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Davidsonia Dec 1, 1980

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VOLUME    11 NUMBER    4
Winter 1980 Cover:
Tsuga mertensiana in an
alpine setting.
A shrub in the snow, showing how snow collects
in the angles of the branches, possibly causing
snapping of the branch.
VOLUME    II NUMBER    4 Winter 1980
Davidsonia is published quarterly by The Botanical Garden of The University of British
Columbia, Vancouver, British Columbia, Canada V6T 1W5. Annual subscription, ten
dollars. Single numbers, one dollar and fifty cents, except for special issues. All information
concerning subscriptions should be addressed to the Director of The Botanical Garden.
Potential contributors are invited to submit articles and/or illustrative material for review
by the Editorial Board.
© 1980 by The Botanical Garden, The University of British Columbia.
The pen and ink illustrations are by Mrs. Lesley Bohm. The article on Tsuga mertensiana was
reviewed by Dr. Oscar Sziklai of the Faculty of Forestry at UBC, who also provided some
additional information. Dr. John Neill, Department of Plant Science at UBC, provided information on plants for the Climatological Summary for 1980.
ISSN 0045-9739
Second Class Mail Registration Number 3313 British Columbian Plants in Winter
Winter in British Columbia, as in any temperate region, is a season of relatively short days, low light intensity and cool temperatures. The low temperatures are, directly or indirectly, the most hazardous of these conditions for plants. They reduce the rate at which living cells can perform vital functions, and, when
temperatures fall below freezing, they bring the possibility of ice formation and the accompanying danger of
cell freezing. Ice formation within cytoplasm is always lethal.
British Columbia may be divided into three regions based on expected minimum winter temperatures. The
southwestern Mainland and Vancouver Island are relatively mild with very little probability of the
temperature falling to -40°C. The central and southern Interior, approximately south of the latitude of Prince
George, is a region with some probability of the temperature falling to -40°C. The northern half of the Province has frequent winter low temperatures below -40°C. The -40°C temperature that defines these zones is not
arbitrary. Pure water can be cooled without ice formation (supercooled) only to -37.1 °C, while plant solution
water can be supercooled to -41 °C. Thus, a plant that is only rarely subject to -40°C can theoretically survive
without freezing.
Snow may present a mechanical hazard, causing, for example, broken or bent branches. However, it also _ _
provides excellent insulation against extreme cold and thereby reduces the risk of damage by ice and cell OO
Heavy rains in winter also present problems. Apart from erosion, which may disturb root systems, the raising of the water table may lead to waterlogging. If the water freezes in the soil, it will add to the stresses experienced by the plants.
In spite of the rigorous conditions, winter slows but does not stop life processes. The conditions essential
for survival must be maintained and preparations for spring must proceed. Events occur slowly, but they stop
only with death.
The Advanced Warning of Winter
The seasons follow each other with regularity in the cycle of a year. There is considerable synchrony between the season and the events that take place inside plants. These events include preparations for oncoming seasons. There appear to be two major signals of approaching winter. Plants can detect the shortening of
daylength with progression through the months of July, August and September. Several responses to this
signal are known, including completion of seed and fruit formation and, in deciduous plants, preparation for
leaf abscission. Shortening days bring less and cooler sunlight, which brings the second signal for
winter — lower temperatures. The lower temperatures and short daylength seem to trigger events that
together provide winter protection for plants. Plants that can survive sub-zero temperatures are said to be
cold-hardy. Shortening days and low temperatures are the major signals, but there are probably other stimuli
received from the changing environment that contribute to the attainment of the cold-hardy state.
Response to the Signals — Preparations for Winter
Plants seem to have two major ways of reacting to the approach of winter. They adopt a strategy of cutting
potential losses, and they develop protective states. The result is that overwintering parts resist conditions
that would have lethal or seriously deleterious effects when the plant is growing actively at other seasons.
Cutting the Losses
Annuals, withering biennials, and withering and deciduous perennials reduce body exposure in winter. Annuals avoid many of the winter stresses by renewing the whole plant body each year. The shortening days and
lower temperatures trigger the completion of sexual processes, flowering and seed development, for produc-
*lain E.P. Taylor, Department of Botany, University of British Columbia, Vancouver, B.C. V6T 2B1 FIGURE 1. Snow-covered conifers, showing the
bending of the leaders caused by the weight of the
tion of the next generation, as well as initiating events that lead to the death of the parent. The embryo within
the seed is provided with protection against winter and with the means to restart growth in the next season.
The signals of approaching winter initiate the processes of leaf abscission in deciduous perennials. Enzymes are produced by cells at the base of the petiole. These work to dissolve the walls between the cells,
thus weakening the union between leaf and stem to such an extent that the leaf can be blown off the plant or
fall by its own weight. The same signals also lead to aging of the leaf cells and more or less recovery of
nutrients from the leaf before leaf fall. Furthermore, the cells immediately below the abscission zone are
stimulated to develop into a layer of corky tissue, which becomes the familiar leaf scar. The loss of leaves
before the arrival of winter thus reduces the surface of the plant that could be injured and from which the
plant could lose water by evaporation during a period when replacement is difficult.
The deciduous habit is usually associated with tree or shrub forms. However, several herbaceous perennials and biennials are deciduous, being referred to as "withering" or "dying back". We believe that the triggers leading to withering are the same as those that initiate other winter preparations. The withering biennial
form is uncommon in the British Columbia flora. It is restricted to four families (Apiaceae, Asteraceae,
Boraginaceae and Lamiaceae) and fewer than 10 species (Caraway, Carum carvfi; Poison Hemlock, Conium
maculatum; Wild Carrot, Daucus carota; Wild Parsnip, Pastinaca sativa; the Greater and Lesser Burdock,
Arctium lappa and A. minus; Common Houndstongue, Cyanoglossum officinale; and American Dragonhead,
Dracocephalum parviflorum). It is also of note that the overwintering structure is usually a taproot.
The withering perennial is a common form that seems to differ from the withering biennial in having a
variety of overwintering structures. The events within the withering parts appear similar to those in aging
deciduous leaves. There are color changes, which are associated with the degradation of the photosynthetic
and other pigments, and there is a substantial export of nutrient substances to the overwintering structures.
The effect is the same, namely to reduce the bulk of plant body that can be damaged by the adverse climate.
"•AH species Latin and common names and data on plant habit and flowering times are taken from: Taylor, R.L. and B. Mac-.
Bryde. 1977. Vascular Plants of British Columbia: A descriptive resource inventory Technical Bulletin No. 4, The Botanical
Garden, The University of British Columbia. University of British Columbia Press, Vancouver, B.C. Development of Protective States
1. Dormancy. The term 'dormancy' is generally used to describe a state of suspended activity in plants.
Release from dormancy usually requires special environmental conditions. It is this requirement that
distinguishes dormancy from 'quiescence', which refers to a non-growing state caused by the absence of one
or more of the basic conditions for normal growth, such as temperature or oxygen. Dormancy is known from
many plants and plant parts. Winter dormancy is usually induced by shortening days and lowering
temperatures, and, in many cases, release from dormancy is brought about by the conditions of winter itself.
Seeds, buds and other overwintering structures become dormant in the fall and are thereby stopped from further growth in the event of an 'Indian Summer' or unusually warm early winter weather. In the Interior
Douglas Fir {Pseudotsuga menziesii var. glauca) the seed becomes dormant in the fall and remains so until it
has been chilled at less than 5°C for about 2 months, after which time it can germinate when conditions
allow, usually in March or April. There are many types of winter dormancy. Seeds of the aquatic Nemophila
species are inhibited from germinating by light. The passage of winter seems to provide time for the seed to
be covered with debris and settling silt. Many legumes have hard seed coats that require the activity of
microbes or abrasive damage before becoming permeable to the water and oxygen needed for germination.
Heavy winter rains, which mix the seed with small gravel, may be enough to cause the required damage. The
naturalized annual Cockleburs (Xanthium spp.) produce two seeds in each fruit, one that is not dormant and
one that requires damage for access of oxygen. In other species, the seed coat contains inhibitory chemicals
that must be leached out by rain before germination can proceed.
A contrasting example is provided by Downy Birch (Betula pubescens) in which the dormancy induced in
fall is not released by the passage of winter, but requires the occurrence of mid-summer conditions (both long
days and temperatures in excess of 15°C).
The induction and control of dormancy are little understood, but it seems that several mechanisms known
from seeds have parallels in buds and other structures.
2. Surviving as an evergreen. Winter annuals and evergreen biennials and perennials face the winter with living structures above ground and exposed to the elements. Reaction to the signals of approaching winter
seems to involve many cellular changes. All plants contain a considerable amount of freezable water. Most
plants are killed if frozen during active growth in summer. The evergreen plants and the remaining parts of
others survive winter by tolerating or even avoiding freezing if they are allowed to cold acclimate, that is,
become cold-hardy. Clearly the events of fall are critical to winter survival. There have been several studies
on the biochemistry of cold acclimation, and it is clear that no one mechanism has been identified. The
chemical composition of cell membranes and cell contents have been found to change during acclimation,
but these changes have not been rigorously demonstrated to be the causes of resistance to winter.
A few annuals germinate in the fall and overwinter as seedlings ready to grow whenever the weather improves. Among these so-called winter annuals are the agriculturally important winter rye and wheat, and
more than 30 other species occurring in British Columbia, including Cornflower (Centaurea cyanus), Common
Ragwort (Senecio vulgaris), Shepherd's-purse (Capsella bursa-pastoris), Wild Radish (Raphanus raphanistrum),
Spurred Gentian, (Halenia deflexa), and Rosy Gilia (Cilia sinuata). These plants seem not to become dormant.
Rather, they are quiescent and are able to take advantage of warmer weather while possessing considerable
hardiness. Biennial evergreens, e.g., Foxglove (Digitalis purpurea), overwinter in a low profile form, which is
also capable of some growth prior to the season of reproductive growth that occurs in the second summer.
Evergreen perennials are either low profile herbaceous and shrubby plants that can survive compression
against the soil, or woody shrubs and trees that are physiologically acclimated against their exposure.
Whatever its form and habit, the evergreen must survive the winter bearing the same structures (leaves)
that in summer perform some of the major processes of plant life. The summer leaf traps sunlight with immense efficiency, provides an efficient cooling and gas exchange system, and contains the machinery that we
believe is concerned with the fine timing of reproduction. In winter that same leaf must avoid damage and
reduce photosynthesis and evaporation. The development of cold hardiness is vital to survival.
How Plants Tolerate the Cold
Once preparations for winter are under way, the remaining plant or plant parts must survive the unfavorable conditions. The danger of damage is constantly present. The commonest frost- and ice-caused injuries include frost splitting of tree trunks, black heart in woody stems, and crown kill of winter cereals and
herbaceous perennials. In spite of often extreme conditions, we find effective morphological and
physiological tolerance to winter, and even considerable development and metabolic activity in the case of
winter flowering and evergreen forms Morphological Devices for Cold Tolerance
Both biennials and perennials use the bud as a protective structure for the shoot tip growing zone, or
meristem. The overwintering bud consists of a series of scale layers around the miniature leaves and/or
flowers that will emerge as new growth in the next growing season. The scales of some buds are tightly
wrapped, e.g , the Maples (Acer spp.), whereas others, like Red Alder (Alnus rubra), have their male catkins
clearly visible but not open.
The woody stems of shrubs and the trunks of trees also serve as overwintering structures. In deciduous
forms, the remaining aerial parts serve to store materials recovered from the leaves before the onset of winter
and sequestered in the living parenchymatous tissue (xylem or ray parenchyma) within the wood It has long
been thought that the increased solute concentration within these cells provided some type of anti-freeze
mechanism; however, recent studies indicate that the matter is somewhat more complex. The outer bark of
woody stems provides further insulation against the extreme air temperatures that trees must withstand
Rhizomes, stem tubers, root tubers, corms, bulbs and tap roots are underground overwintering structures
from which new growth and some asexual reproduction can occur. The soil provides considerable protection
for plants, even when it is frozen. The air in spaces between soil particles, and even the ice itself, provides
substantial insulation against the much more variable air temperature above ground. Similarly, snow cover
serves to stop ground temperatures falling much below 0°C, as well as protecting low profile evergreens from
more intense cold.
The seed, whether it be dormant or merely quiescent, is a structure designed for hardship. Much of its
resistance to cold, apart from dormancy mechanisms, seems to be due to its relatively low water content.
FIGURE 2. Vacc;ni'um sp  in winter, only the buds
and stems are exposed. Seeds can remain air dry for some time, a property that is exploited in various seed storage practices.
However, in nature most seeds do not spend much time dry. They are usually released from the parent plant,
imbibe some water, and survive the winter in this somewhat dehydrated but cold resistant state.
Frost Hardiness — A Physiological Device for Cold Tolerance
Jacob Levitt, who worked at the University of Missouri for many years, identified three general means of
achieving frost hardiness:-
a) Dehydration of freezable tissue water before winter. Plants lose water by evaporation, and the
cell chemicals bind the remaining water in such a way that it cannot freeze. Several lichens use this strategy.
When dehydration is complete, the tissue becomes extremely dry and brittle, and the cells, although cold,
cannot freeze.
b) Supercooling (undercooling) of tissue to below normal freezing point. Pure water freezes at 0°C
and water in plants can freeze at-5°C. However, some plants do not freeze until the temperature falls to the
point at which it is physically impossible to stop ice crystal formation (approximately -40°C). Plants possessing this mechanism thus avoid tissue ice formation and the danger of intracellular freezing in all but the
coldest of winters. In areas where temperatures fall below -40°C, these types of plants can only survive if they
are protected by snow or can tolerate some injury. Some 70 species of deciduous hardwoods native to eastern
North America are known to supercool, but the phenomenon is not known in British Columbian hardwoods,
such as Willow, White Birch and Trembling Aspen, nor in conifers. There have been reports that Kinnikinnick
(Arctostaphylos uva-ursi) and Prickly Rose (Rosa acicularis), both woody shrubs native to British Columbia, do
have supercooling of their xylem ray parenchyma, and thus the ability to survive to -40°C. Our present limited
information is that supercooling is restricted to localized regions within the plant, such as xylem rays and
floral primordia. This localization provides protection to vital parts and reduces the general damage that
would occur if the whole plant supercooled. If this were the case, the chilling of one exposed supercooled
part to below -40°C would lead to ice formation in that part, and this would be followed by rapid and total
freezing of the whole plant, which, in turn, would be lethal. In fact, the centres of supercooling are protected
and insulated by the bud scales around primordia and by the bark outside the xylem. Clearly the system is not
stable enough to withstand extensive exposure to -40°C temperatures, and this is believed to be the reason
that supercooling has not been reported from plants that grow in the far north.
c) Extracellular freezing of water. Although intracellular ice formation is always lethal, the formation of ice in the cell walls and intercellular spaces is a common occurrence in many intermediately hardy
and very hardy plants. The ice crystals that form first act as growth points and draw water out from the living
cells, thereby creating conditions of physiological drought (water present but not available to the cells). Ice
formation is quite slow, and, as ice is a bad heat conductor, it may provide some insulation for the living
material within. In addition, the liquid water remaining, like that in dehydrated lichens, is so tightly
associated with cell constituents that it will not freeze. The introduced Black Locust tree (Robinia
pseudoacacia) is so well protected by this mechanism that its bark can survive freezing to -196°C, the
temperature of liquid nitrogen It is likely that most of the plants in the British Columbia Interior fall into this
category, but it is to be expected that the degree of frost hardiness achieved by this method will vary between
species and from winter to winter We may speculate that environment will determine the extent of hardening, but we do not know the details.
Activity in Winter
Winter in the coastal regions of British Columbia is far less severe than in the interior of the province The
higher air temperatures and the generally milder conditions provide greater opportunity for growth and
development, as well as reduced hazard. Many plants can photosynthesize at temperatures close to 0°C and
root growth may occur, albeit slowly. Several species flower in the winter months, including the California
and Beaked Filberts (Corylus cornuta var. californica and C. cornuta var. cornuta), Common Whitlow-grass
(Erophila verna), Western Birch (Betula occidentalis), Common Corn Spurrey (Spergula arvensis), Common Star-
wort (Stellaria media), and Annual Nettle (Urtica urens).
Overwintering evergreens develop various degrees of hardiness, but retention of the leaves throughout the
year presents several problems that are not faced by the seemingly better protected deciduous and withering
plants. Winter sunshine provides the leaves with enough energy for the performance of photosynthesis and
transpiration, although the incidence of both light and heat energy is much reduced.
The opening of stomata for photosynthesis is at the expense of water loss by transpiration through the same
stomata — water that is not easily replaced from cold or frozen soil. Evergreen plants may thus become
seriously water deficient with the passage of winter. There are several leaf modifications that serve to reduce this water loss. Many evergreens, for example, conifers, Labrador Tea (Ledum spp.), English Holly (Ilex
aquifolium) and Salal (Gaultheria shallon), have thick waxy cuticles on the upper, more exposed surface of
their leaves. The water-repellent nature of this cuticle provides a barrier across which water cannot easily
pass. In addition, the reflective properties of the wax contribute to the reduction of light entering the leaf,
thereby cutting down the heat that must be dissipated by evaporation. Water loss is also reduced by the confinement of stomata to the more shade protected lower side of the leaf, and by their insertion below the leaf
surface. There is some thickening of cuticle on the lower surface, and in some cases there is a layer of protective hairs. All of these modifications serve to reduce water loss by the creation of a humid air layer below the
leaf, which is not easily disturbed and which forms a barrier to diffusion between the saturated inner atmosphere of the leaf and the often drier air outside. A behavioral water-conserving modification is hyponasty,
which reduces evaporation and the incidence of light energy by causing the leaves to become reflexed.
Pacific Madrone (Arbutus menziesii) shows this reaction, in which the leaves change their orientation from
more or less perpendicular to parallel with the direction of sunlight by folding backwards along the stem. The
effect is to increase undisturbed air volume close to the lower surface of the leaf (reducing transpiration) and
to reduce the light striking the leaf by presenting less of the flat blade and more of the margins to the path of
the light. This reaction is also shown by Rhododendron species.
These and other devices seem to provide the evergreen plant with protection against extreme conditions
while allowing some growth and development when conditions are favorable.
Preparations for the Spring
Although only a few systems have been studied, it seems likely that all plants undergo some changes during the winter that are preparatory for the coming of spring. The signals are lengthening days and warmer
temperatures. Non-dormant plants are free to grow whenever conditions permit, but those showing dormancy
must be released from that state before they can begin the new season's growth. We saw earlier that there are
many dormancy mechanisms and it is reasonable to expect that each will have its own particular release processes. Two plant growth regulators have been implicated in the control of certain types of dormancy, including after-ripening and cold treatment release. Abscisic acid seems to play a major role in the induction of
dormancy. Its action is thought to be that of a growth inhibitor, and it has been isolated in significant amounts
from both dormant seeds and dormant buds. One or more of the gibberellin hormones (there are over 50) is
thought to have a function in the release of dormancy. As the amount of the gibberellin(s) present increases,'
and as the abscisic acid levels fall, the dormant structure progresses towards release Apart from this information, we have very little understanding of the changes in plant hormone status in the winter
Whatever the cause, most plants are ready to restart their growth during the early spring All they require is
warmth, moisture and light.
There are over 2500 vascular plant species in British Columbia Ecologists recognize several biogeoclimatic
zones within the province (see Davidsonia 7:45-55), each of which has characteristic winter conditions. Plants
survive winter by receiving signals from the environment and by reacting to those signals. The variety of
plants and the variety of conditions suggest that plants have adopted many strategies to deal with winter.
There may be some universal patterns, but it is likely that each species will have its own pool of responses
from which to draw. Selection from that pool may well be a function of the local environment
It is true that we understand very little about plants in winter, and the flora of British Columbia is no better
studied than any other. However, the current interest in the cultivation of native plants and in gardening in
the Interior provides some incentive to study things in greater depth. The suitability of plants for cultivation
depends on many things, not least in British Columbia being the ability to develop hardiness and resist winter
conditions. In selecting varieties for cultivation, it is important not only to select hardiness but to ensure that
improvement programs include the consolidation of the genetic determinants for frost resistance.
I thank Dr. Mark Tepfer for helpful criticism during the preparation of this article REFERENCES
Dr. Taylor has suggested the following references for those people who wish to read further on the subject of plants in
Levitt, J , Ed 1980 Responses of plants to environmental stresses Vol 1. Chilling, freezing and high temperature stresses.
Academic Press Inc., New York.
Underwood, L.S., L.L   Tieszen, A.B   Callahan and G E. Folk, Eds. 1979. Comparative mechanisms of cold adaptation.
Academic Press Inc , New York
Vilhers, T A. 1975 Dormancy and the survival of plants. Studies in Biology #57, Edward Arnold (Publishers) Ltd., London.
Weiser, C J   1970. Cold resistance and injury in woody plants. Science 169:1269-1278.
In addition to the above references, the results of research on cold acclimation and hardiness are reported in several
botanical journals, such as the Canadian Journal of Botany, Plant Physiology and Physiologia Plantarum. Magazines such
as Nature Canada, Audubon and National Geographic have all published excellent essays and photo-essays on various
aspects of plants in winter
71 Mixed Hanging Baskets
A hanging basket need not be just a flash of summer color. With carefully chosen plant material and
seasonal modifications, a miniature hanging garden can be created as a focal point of interest enhancing its
background for year-round pleasure.
To ensure an interesting and long-lasting summer display, various factors should be taken into consideration.
The amount and intensity of sunlight required by plants varies, therefore material with similar requirements
should be used for each location chosen
A suitable mixture of plants should include both background and/or foliage plants to enhance flowering
and/or color-giving plants.
Some plants bloom throughout the summer, while others have a definite season. Early-flowering plants
generally bloom when the basket is planted in spring and finish about mid-summer, while late-flowering
plants begin to bloom in mid-summer and last into the fall. A combination of early- and late-flowering plants
allows a greater number of species to be used, and the display, as well as the color scheme, will vary
throughout the season.
The choice of color is a highly individual one, but it should be kept in mind that the amount of light and the
distance of viewing play an important role. White and light-colored flowers brighten a dull shady spot, and
are more visible from a distance. Such colors also give an illusion of coolness to a hot sunny area. Dark and
brilliantly colored flowers may tend to merge into the background on a dull day, but will look rich and glowing on a sunny day.
When using plants with variegated foliage, choose ones with a bold and clearly-defined pattern, as they
will have a cleaner, crisper appearance from a distance
It is a sad fact that most plants used in baskets have little or no fragrance. Scented Geraniums
(Pelargonium) and Plectranthus coleoides cv Marginatus are exceptions and have a pleasant aroma when
It is possible to continue the display through the winter by removing spent tender plants from the baskets in
the fall and replacing them with hardy ones. Obviously, the display in our climate will have to depend, to a
very large extent, on a pleasing mixture of different colors, textures and patterns of foliage, both plain and
variegated. However, most of the factors to consider for a summer display apply equally well for a winter
basket (Figure 3).
A mixed basket can be divided into three specific layers:-
1. Upright-growing plants to provide height.
2. Bushy, floppy and spreading plants to soften the edges of the container.
3. Long trailing plants to add grace and luxuriance.
Plants from each category should be used in the same basket for maximum effect Thus, it is important to
know the habit of growth of the plants used. For example, Fuchsia cultivars with upright, arching or completely trailing habits are available. In our experience, with few exceptions, single or small-flowered Fuchsia
varieties perform better than double or large-flowered ones, as they are more floriferous and the habit of
growth is more attractive.
"Staff  Members,  The  Botanical  Garden,  The  University of   British  Columbia,  6501   NW Marine  Drive,  Vancouver,
B.C.    V6T 1W5 FIGURE 3. A winter hanging basket The plants
include (clockwise from centre back) Arundinaria
variegata, Tsuga canadensis, Rubus tricolor, Sar-
cococca hookerana var. humilis (right centre),
Hedera helix, H. helix cv. Conglomerata, and Cryptomeria japonica
There are a multitude of containers available on the market. When choosing a container, keep in mind that
ones with straight sides hold more soil, and also that an adequate opening for proper drainage is necessary. As
a basketful of soil and plants can easily weigh 16 kg (35 lbs.) or more by the end of the season, it is obviously
important that the hanger and the support be sturdy enough to carry the weight
The two classic types of containers are the wire basket and the wooden lattice basket, both of which require lining with moss before adding the soil. They have an advantage over the other containers in that small
plants can be planted around the sides and bottom by inserting them through the moss. Their disadvantage is
that they dry out faster than solid containers.
Garden shops generally sell commercially mixed soilless composts that are especially suited for the local
climate They are a better choice for use in a hanging basket than garden soil, which is often too heavy and
may not drain sufficiently well.
When planting a basket, well-established plants of equal size should be used. Avoid small seedlings and
newly established material. All the plants chosen must require or tolerate the same growing conditions, plus
be vigorous enough to stand the fierce root competition in the small, crowded space of the container.
Strong-growing annuals, such as Impatiens and Schizanthus, initially should be controlled by removing
some of the basal leaves or they will smother the surrounding growth of other plants. The shoots from trailing plants should be prevented from growing towards the centre of the basket, so that all the growth may be
directed into the trailing shoots.
The location chosen should be convenient for maintenance, and where water drips will cause no problems
to either plants or surfaces below. A windy site should be avoided, to prevent excessive drying out and
damage to soft foliage. If possible, a winter basket should be positioned in a location out of the wind and
under an overhang or other cover to protect it from too much rain and light frosts. Plants suspended in the air
are far more vulnerable to frost damage than those growing in the ground. It would be wise to remove the
basket to a warmer location if a severe or prolonged frost is expected.
Hanging baskets should always be watered thoroughly, until water drains freely from the bottom of the
container. If a basket has become very dry, repeat the process until the centre is completely moistened again.
The frequency of watering will depend on exposure, temperature, wind, and the plants used. Plants in a
basket, especially those growing under cover, will appreciate an overhead sprinkling of water at intervals, to
clean and freshen the foliage.
Container-grown plants quickly exhaust the nutrients in the soil, therefore a feeding schedule should be
established to maintain their vigour and good health. A fertilizer such as 20-20-20 with trace elements may be
used approximately once a week when the basket has become established. In general, plants in hanging
baskets benefit from lighter, more frequent feedings than plants in the ground.
Hanging baskets are highly susceptible to air-borne insects. The two most common ones to cause trouble
are aphids and spider-mites. A weekly inspection will allow detection and control of an infestation, before it
gets out of hand, by using an insecticidal aerosol. A chronic infestation should be treated with a systemic insecticide. Diseases are generally not a problem if plants are kept healthy, and dead plant material removed
FIGURE 4. Heterocentron elegans, Spanish-shawl,
is a trailing plant with solitary purple flowers, 2.5 cm
in diameter. FIGURE 5 (right)   Acaena buchananii is a creeping
alpine plant from New Zealand.
FIGURE 6 (below) Solanum jasminoides cv Album,
White Potato Vine, has white star shaped flowers
in branched cymes.
75 Plants to Use in Hanging Baskets
Plants for sale in nurseries or listed in books are generally labelled as being suitable for Perennial Borders,
Rock Gardens, etc. If one can get into the habit of looking at plants without categorizing them into such
groups, there are a multitude of possible candidates for use in hanging baskets. During 1980 we tried several
unusual plants with varying success.
Two unusual plants that we used were Acaena buchananii and Diascia X 'Ruby Field' (D. barbarae x D.
cordata). Acaena buchananii (Figure 5) is a creeping alpine plant from New Zealand, normally used as ground
cover in the rock garden. The plant is 1.25 cm high and has small, divided, pale mauve-grey leaves with a
glaucous surface. The flowers are insignificant. Acaena buchananii performed well as a trailing plant in its
first year, except for the fact that we started with rather small plants so that the trailers only reached about 75
cm long. The best features of this species are that it supplies a unique color and a distinctly different texture
from other trailing plants. It is a beautiful foil for pink and rose colored flowers.
Diascia X 'Ruby Field' (Figure 7) is another plant borrowed from the rock garden. It is related to
Schizanthus and, indeed, looks like a salmon- to strawberry-pink form of this species. Diascia will send up its
wire-fine flower stems bearing up to 15-20 flowers from May until September without slowing down or setting
seed. The flowers are nearly 2 cm in diameter. The plants used in the mixed baskets did not perform too well
because they were too small and not well enough established. However, seven small plants placed in a
wooden lattice basket in January 1980 began to flower in the greenhouse about March 15 The basket was
hung outside in May, and looked like a beautiful pink cloud until well into the fall
The possibilities for trying out new and different plants are endless Among the plants we are proposing to
try next year are a purple four-leaved form of the common garden and roadside weed White Clover, Trifolium
repens 'Atropurpureum'; a 45 cm high variegated Bamboo, Arundinaria variegata (often listed as Pleiobastus
fortunei 'Variegatus Pygmaeus'); and Dicentra eximia cv. Zestful, a well-known border plant with a long
blooming season and bearing gracefully pendant, deep pink flowers.
FIGURE 7 Diascia x Ruby Field' has pinkish
flowers that are nearly 2 cm in diameter, and will
bloom throughout the summer APPENDIX. Unusual Plants to Try in a Hanging Basket.
To compile a list of plants suitable for use in hanging containers would be an enormous task, since most plants will grow
suspended in the air, indeed some require it. Most good all-round gardening books contain a section or chapter dealing with
the subject, and will have lists or tables of the more commonly-used species and their varieties.
The plants in the following list have been chosen as possibilities, and range from alpines and shrubs to grasses, from
hardy to tender, and with habits from upright through bushy to trailing. The L.H. Bailey Hortorium book Hortus Third has
been used as the standard for the names and authorities wherever possible.
Trailing Plants
Acaena buchananii Hook. f. (Rosaceae)
Artemisia stellerana Bess (Asteraceae)
Convolvulus mauntamcus Boiss. (Convolvulaceae)
Cotoneaster   dammeri   C.K    Schneid.   (compact   form)
Cotu/a squalida (Hook f) Hook. f. (Asteraceae)
Felicia amelloides L (variegated form) (Asteraceae)
Geranium sanguineum L (Geraniaceae)
Hedera helix L  cv. Gold Heart (Araliaceae)
Helichrysum petiolatum (L ) DC. (Asteraceae)
Heterocentron elegans (Schlecht.) O. Kuntze (Melastom-
ataceae) (sometimes known as Schizocentron elegans)
Lathyrus latifolius L (Fabaceae)
Lysimachia nummularia L. (Primulaceae)
Lysimachia nummularia cv. Aurea
Plectranthus coleoides Benth. cv. Marginatus (Lamiaceae)
Polygonum   capitatum   Buch.-Ham.   ex   D.   Don   (Poly-
Polygonum vaccinifolium Wallich.
Rubus nepalensis (Rosaceae)
Rubus tricolor Focke
Solanum jasminoides Paxt. cv. Album (Solanaceae)
Trifolium repens L. cv. Atropurpureum (Fabaceae)
Verbena peruviana (L ) Britt (Verbenaceae)
Waldsteinia ternata (Steph ) Fritsch (Rosaceae)
Bushy Plants
Arabis caucasica Schlecht. cv   Variegata (Brassicaceae)
(also known as A. albida cv. Variegata)
Artemisia stellerana Bess. (Asteraceae)
Coronilla varia L. (Fabaceae)
Dianthus x allwoodii Hort. (Caryophyllaceae)
(also known.as D. alpinus L. cv Allwoodii)
Diascia   x   'Ruby Field' (Scrophulariaceae) (D   barbarae
X D. cordata)
Euonymus fortunei (Turcz.) Hand Mazz  cv Emerald and
Gold (Celastraceae)
Euonymus fortunei var  radicans (Siebold ex Miq) Rehd
cv. Silver Queen (often cited as E. fortunei cv. Silver
Euryops acraeus M.D. Henders (Asteraceae)
Euryops pectinatus Cass.
Felicia amelloides L. (Asteraceae)
Felicia amelloides (variegated form)
Geranium sanguineum L (Geraniaceae)
Geranium wallichianum D. Don ex Sweet cv Buxton's Blue
Hedera helix L. cv. Conglomerata (Araliaceae)
Helichrysum petiolatum (L.) DC. (Asteraceae)
Lamium maculatum L. (Lamiaceae)
Lamium maculatum cv. Album
Oplismenus hirtellus (L.) Beauv. cv. Variegatus (Poaceae)
Parahebe catarractae (G. Forst.) W. Oliver (Scrophulariaceae)
Pelargonium cvs. "Scented Geraniums" (Geraniaceae)
Penstemon hartwegii Benth   cv. Garnet (Scrophulariaceae)
(often listed as P. 'Garnet')
Plectranthus coleoides Benth. cv. Marginatus (Lamiaceae)
Potentilla davurica.Nestl. cv. Beesii (Rosaceae)
Solanum jasminoides Paxt. cv. Album (Solanaceae)
Stenatophrum secundatum (Walt.) O. Kuntze cv. Variegatum
Tolmiea menziesii (Pursh) Torr. & A Gray (variegated form)
Trifolium repens L cv Atropurpureum (Fabaceae)
Verbena peruviana (L.) Britt (Verbenaceae)
Wahlenbergia gloriosa Lothian (Campanulaceae)
Upright Plants
Arundinaria variegata Miq. "Dwarf Whitestripe Bamboo"
(Poaceae) (also known as Pleiobastus fortunei cv Variegatus Pygmaeus)
Cuphea cyanea Moc & Sesse ex DC (Lythraceae)
Dicentra eximia (Ker.-Gawl.) Torr. cv. Alba (Fumariaceae)
Dicentra eximia cv. Zestful
Euonymus fortunei var radicans cv Silver Queen (Celastraceae)
Euryops pectinatus Cass. (Asteraceae)
Festuca ov/na L. var glauca (Lam.) W D.J. Koch (Poaceae)
Geranium endressii J Gay (Geraniaceae)
Hedera helix L cv. Erecta (Araliaceae)
Hedera helix cv Ivalace
Mentha x gentilis L. (Lamiaceae)
Mentha x rotundifolium (L.) Huds. cv. Variegatum
Milium effusum L. cv. Aureum (Hoaceae)
Nandina domestica Thunb. cv Nana (Nandinaceae)
Sarcococca hookeriana  Baill. var. humilis Rehd. &
Verbena rigida K. Spreng. (Verbenaceae)
Wils. Tsuga mertensiana in British Columbia*
Mountain Hemlock
Member of the Family Pinaceae
Natural Distribution and Habitat
Tsuga mertensiana (Bongard) Carriere occurs from southeastern Alaska (Kenai Peninsula, 61°10'N) south
through western British Columbia, Washington and Oregon to the southern fork of the King's River (36°40'N)
in northern California. It also extends eastward to the western slopes of the Selkirk Mountains in southeastern
British Columbia, and south to western Montana, the Bitterroot Mountains of northern Idaho, and the Blue
Mountains of northeastern Oregon. The tree is found at subalpine to alpine elevations throughout its range,
from 1800-3350 m in California and descending gradually northwards to 0-1220 m in Alaska. The species
usually prefers a northern exposure, because of the cool moist soil conditions. It reaches its best development
on loose, coarse, moist but well-drained soils on flat land and gentle slopes and at the heads of moist valleys
or sheltered ravines, but will grow well on a wide range of soils except those derived from peat. It does not
grow on calcareous soils. The best stands of Tsuga mertensiana are found along the broad crest region of the
Cascade Mountains in central and southern Oregon The species is usually stunted in high exposed situations.
The climate throughout the range can be characterized as having long cold winters, short vegetative seasons,
and high precipitation, with most of it falling as snow. The tree is a major component of the Mountain
Hemlock-Subalpine Fir forests throughout the range, and may occur in uneven- or even-aged pure stands, or
in association with other species, such as Alpine Fir, Engelmann Spruce, Alpine Larch, Whitebark Pine, and
Lodgepole Pine.
In British Columbia, Tsuga mertensiana is common in the alpine and subalpine zones of the Coast from
760-1524 m in the south to 300-900 m in the north, and also in the Interior of the Province from 1220-1800 m.
It is present between 305-1525 m on all mountains on Moresby and Graham Islands in the Queen Charlotte
Islands. The species extends eastward through the Fraser River Valley on the higher slopes above 820 m to
Silver Mountain near Yahk. It may also occur at lower elevations on poorly drained soils where other species
offer little competition. The soil in which it occurs in British Columbia is commonly a mor humus, with a pH
of 3.1-3 9. The mean annual temperature is 1-5°C with 50-100 frost-free days, and 2200-4300 mm precipitation, mainly falling as snow in the fall and winter. In both British Columbia and Alaska, the species is capable
of pioneering on glacial moraines, and also of invading and establishing in heath communities, although it
does not grow well on such soils. It is commonly associated in the Province with Sitka Spruce, Yellow Cedar,
Pacific Silver Fir, Western Hemlock, and Alpine Fir
Tsuga mertensiana is an evergreen species varying from a stunted or sprawling shrub on high exposed ridges
to a medium or large tree in sheltered locations. It is usually (2-15-)20-40(-50) m tall, with a diameter of
(12.5-)25-75(-150) cm. The crown is narrow and pyramidal, with slender, horizontal to drooping branches irregularly arranged along the trunk, but becoming irregular and bent or twisted with age. The leader is slender,
flexible, and drooping. Open-grown trees develop a strongly tapered trunk bearing slender branches almost to
the ground, and the crown is narrowly pyramidal. In dense stands, the trunk is more cylindrical, becoming virtually clear of branches with age, and the crown only covers the upper half or less of the tree. On steep slopes
the trunk may have a basal sweep, rather like a sled runner, as a result of heavy snows bending the slender
There is a shallow but widespreading root system.
The bark on older trees is 25-35 mm thick, grayish or dull purplish to dark reddish-brown, and strongly furrowed into rounded, flat-topped ridges covered with closely appressed scales. The inner bark is cinnamon-red
*By Roy L Taylor and Sylvia Taylor C X 0.45
15 m,	
1.0 m
0.5 m	
B X 20
0.5 m
FIGURE 8, Tsuga mertensiana. A. Habit, B. dry, open branch tip, C. branch bearing open and closed cones, D. seed and
paired seed scales. or purplish, and the outer bark may show purplish streaks when freshly cut. The trunk may appear to have a
blue-gray tinge from a distance. The bark contains tannin, which gives it an astringent taste.
The twigs are thin and flexible, or sometimes rather stout and rigid, only slightly drooping, and are unequal
in length, with numerous short erect side branches from the upper side of the longer ones. They are reddish-
brown and pubescent with both long and short multi-cellular hairs for the first two or three years, becoming
brownish-gray and scaly with age. The twigs are roughened by the presence of the persistent, woody, peg-like
bases of the leaves, which remain closely appressed against the twigs  The needle scars point forwards.
The wood is non-resinous, light, soft, close-grained, very hard and tough because of the slow growth. The
heartwood is pale reddish-brown, and the sapwood is thin, similar colored to whitish, and not distinctly
separated. The wood has a distinctive odor when freshly cut. It is variable in quality, sometimes being rather
brittle and at other times being of good quality and easy to work.
The winter buds are non-resinous, ovoid with a pointed apex, about 3 mm long, reddish-brown, and both terminal and lateral buds are present. The outer scales have conspicuous midribs elongated into slender,
deciduous, awl-like tips.
The needles are single, (5-)10-25 mm long, 1-1.6 mm broad, dark green to yellowish- or bluish-green, entire
with a bluntly pointed apex, and are usually slightly curved. They are usually rounded or keeled above,
rounded and grooved towards the base beneath, and have stomatic lines on both surfaces, the stomata
sometimes giving a grayish or glaucous tinge to the needles Tsuga mertensiana is unique among the hemlocks
in that the needles are almost equal in length and are radially arranged. They spread from all sides of the
branch and give a star-like appearance. They tend to be closely arranged and crowded on the short lateral
branchlets, giving a tufted appearance, and more remote on the leading shoots. There is one median resin
canal below the vascular bundle. The base of the needle is abruptly narrowed to the short, slender, slightly
twisted petiole The petiole is articulate on a persistent and eventually woody base, which is at least as long
as the petiole The needles are persistent for 3-4 years, and are then quickly deciduous. There is some variation in the needle color in wild specimens of T. mertensiana, with variation from deeply glaucous to bright
clear green.
The strobili ("flowers") appear in June to July over the range. Male and female strobili form on branchlets
of the previous year's growth in separate parts of the same tree (monoecious). The male or staminate strobili
are single, numerous, and axillary on lateral shoots. They are subglobose to globose, 3-4 mm long, bluish to
violet-purple, and consist of numerous, spirally arranged sporophylls ("anthers"). They are pendulous on
slender, pubescent peduncles that are 4-6 mm long. The female or ovulate strobili are solitary or clustered,
erect, and usually terminal on the shoots. They are cylindric to oblong-cylindric, narrowed at both ends,
bluish- or reddish-purplish to (occasionally) yellow-green, and sessile There are numerous, thin, roundish,
woody, imbricated scales. The scales near the centre are fertile, each bearing 2 ovules at the base. Each scale
is subtended by a membraneous bract, which is lustrous dark purple to yellowish-green, and gradually narrowed into a slender, often slightly reflexed tip The bracts vary in length from shorter than to much longer
than the scales.
The mature cones are woody, (1 25-)3-7.5(-8) cm long, 2-2.5 cm broad, and are usually light brown or
reddish-brown, although there is great variation in the color. They are oblong-cylindric, narrowed towards the
blunt apex and somewhat narrowed towards the base, sessile, and erect until more than half-grown, then
usually pendulous. The cones on stunted and exposed trees are often stunted and erect at maturity. Erect
cones may also be found rarely on non-stunted trees. The cones are solitary or in dense clusters, and may be
very conspicuous. The scales are thin, concave, obovate with a blunt apex, and are gradually contracted from
near the middle toward the cuneate base They are puberulous on the outer surface, and the margins are irregularly toothed and sometimes thickened. The scales are usually much longer than the minute, sharp-
pointed, dark purple or brown bracts. They open at right angles to the cone axis at maturity. The cone is
mature in August to late September and October of the first year, and the seed is shed immediately although
the cone axis with attached scales is persistent on the tree until the summer or fall of the following year.
The seeds are 3-5 mm long, light brown, obovate with a rounded apex, compressed, and dotted with minute
resin vesicles. The surface next to the scale may be marked with 1 or 2 large resin vesicles. The testa (outer
seed coat) is expanded to form a thin membranaceous wing, (5-)8-10(-12) mm long, and nearly surrounding
the seed.
Trees begin to bear cones at about 20-30 years of age, a little later if the tree has been shaded. The species
is a prolific seed producer, with some seed produced annually, and heavy crops at 1-5 year intervals. The
seed may be of poor quality in some years, although the reason is as yet unknown. Varieties and Ornamental Cultivars
Intermediate forms between Tsuga heterophylla and T. mertensiana may be found in areas where the
distributions of the species overlap, especially on Mount Rainier and Mount Baker in Washington and on Vancouver Island. Tsuga x jeffreyi (Henry) Henry, Jeffrey Hemlock, is considered to be such a hybrid. It has the
habit of T. mertensiana, but the leaf arrangement and color more closely resembles T. heterophylla. The form
was originally raised in 1851 at Edinburgh from seeds collected in the Mount Baker Range by John Jeffrey,
although the herbarium specimens that he collected at the same time were T. mertensiana. The hybrid was
unknown in nature until about 1940 when Mr. M. Hornibrook in Ireland received some seedling conifers collected in the mountains behind Cowichan Lake on Vancouver Island. One of the seedlings was identical to
the cultivated T. X jeffreyi. Some authorities believe that T. X jeffreyi may be more common in nature than
is usually thought, because they may be passed over as a green-leaved form of T. mertensiana.
There have been two recent studies on the nature of the hybrid forms. Meagher (1976) studied variation in
the two species of Tsuga in southern British Columbia and concluded from his unsuccessful experiments on
hybridization and other data that they were genetically distinct. He found no cones indicative of a true
hybrid. Dr. R.J. Taylor (1978) studied the relationship of Tsuga heterophylla, T. mertensiana and their intermediate forms in western Washington He found that over 300 cones collected after controlled cross-
pollination between the two species did not contain any sound seed. He concluded from chemical evidence
that hybrids do occur, but at an extremely low frequency rate, the failure of cross-pollination indicating a
genetic incompatibility rather than a difference in pollination time or some such mechanical factor. A majority of the physically intermediate forms that he tested were not hybrids chemically, and he therefore concluded that these forms were not hybrids.
Tsuga mertensiana has a long north-south range and grows in a variety of habitats. It is possible that
geographic variation exists in the species, although this has not been documented. Certainly, there is great
variation in needle color in nature, and trees at high exposed elevations are very stunted. Several of the
stunted forms have been collected and have proved to be fine dwarf specimens for the garden. These dwarf
cultivars include:- cv. Cascade, a slow-growing (35-50 mm annually), very compact plant, originally collected
in Oregon; cv. Elizabeth, a spreading form, about twice as broad as high, collected on Mount Rainier in
Washington; cv. Glauca, a very slow-growing form with distinctly glaucous leaves, that eventually becomes a
small tree; and cv Sherwood Compact, which is extremely slow-growing, dense and irregular. In addition, a
form with silvery colored leaves apparently often occurs in seed beds, and is known as cv. Argentea.
There is great genetic variation in Tsuga in general so that plants may not come true from seed. Most lots of
seed show some embryo dormancy, and require a period of cold stratification before germination. The seeds
should be extracted from the cone by tumbling or shaking (a small amount of heat is usually sufficient to
open closed cones).
Tsuga mertensiana seed shows transient viability but may be stored dry in an airtight container atO°C for up
to 5 years or at 18°C for one year. The seed should be stratified in moist sand at 2-4°C for 90 days before sowing in sandy soil, covering the seed to a depth of 0.5-1.0 cm. A germination period of 25-60 days with day
temperatures of 30°C and night temperatures of 20°C should result in 60-75% germination after a further 16
days. The seed may be sown in light sandy moist soil in the garden or in a flat kept in a cold frame or cool
The young seedlings are easily damaged by hot sun and therefore need protection under lath or brush
screens. They grow best in moist humus soil with plenty of atmospheric moisture. Growth is very slow at first,
and the seedlings should not be moved until after the second or third growing season, when they should be
transplanted for one year (to encourage root development) before planting in their permanent position.
Cuttings of at least 2-year old wood should be taken in October and November, wounded, and given a hormone treatment before planting in sandy soil in a greenhouse or cold frame. This treatment should result in a
high percentage of rooting in about 4-5 months. Cuttings may also be taken from December through April
with success.
Crafting may be used to propagate cultivars of all Tsuga, using a side or veneer graft onto an established
rootstock in January or February. However, Tsuga mertensiana grows very slowly from such grafts for the first
10-12 years, and grafting is rarely used In addition, there are many problems with grafts in Tsuga, due to incompatibility, overgrowth of the scion and girdling, and propagation from cuttings is far more common.
There is evidence that Tsuga mertensiana can reproduce vegetatively in nature by layering. Transplanting
Tsuga species can be transplanted easily with a ball of soil around the roots. They are best transplanted in
spring just before active new growth starts, although transplanting in early fall is satisfactory in areas with a
mild climate or if small container-grown plants are used, provided that the soil is moist and in good condition
and the plant is well protected while it establishes. The tops of Hemlocks are usually not pruned on transplanting, therefore the root system must be kept as intact as possible. Trees should not be transplanted from a
shady position to a sunny one, and the trees should be well-guyed after planting. The best results can be obtained by using well-handled nursery-grown material, rather than transplanting from the wild.
Conditions for Cultivation
The growth rate is slow to very slow when young, but increases somewhat after maturity. Tsuga mertensiana
is believed to be a long-lived tree, reaching 400-500 years of age. In nature, trees 46-50 cm in diameter and
15-20 m tall are 180-260 years of age, but on high windswept ridges a tree 60-80 years old may be only
12.5-17.5 cm in diameter. The species is very tolerant and endures shade well, casting dense shade itself.
The recommended hardiness zone in Canada is Zone 4.
Tsuga mertensiana thrives in a great variety of soils from sandy loams to heavy clay and acid soils, but
prefers a deep, cool, moist but well-drained loam. The atmosphere should also be moist and pure, growth in
industrial districts is less than satisfactory. The best development is obtained if the tree is sheltered from
rough winds.
Hemlocks in general require a minimum of pruning, although they will stand a considerable amount of
pruning when necessary, and may even be sheared to form a clipped hedge. The tips of shoots may be
pinched back in spring or early summer to keep the tree within bounds or to make it more compact.
Landscape Value
Hemlocks in general are elegant evergreen trees forming good specimens or clipped hedges.
Tsuga mertensiana is a handsome, decorative tree, with its shapely habit, dense branch system, and
delicate, often glaucous, foliage combining to make it an attractive garden or park specimen. It is also hardy
in the eastern part of the continent, but is little used there. The species is often planted as an ornamental in
western and central Europe.
The species is not planted commercially and forest nurseries are not growing it.
Note that the name Tsuga mertensiana was formerly misapplied in horticulture to 7. heterophylla, and that
species may sometimes still be offered as such.
Other Uses
The wood of Tsuga mertensiana is not commercially important because of the relative inaccessibility and
small size of most trees. However, it is one of the five important conifers of the coastal spruce-hemlock
forests of southeastern Alaska, where the trees are accessible. This wood is marketed with that of Western
Hemlock (T. heterophylla), being similar although somewhat more dense. Mountain Hemlock is also an important part of the softwood saw-timber volume in central and southern Oregon. When marketed, the wood is
used for the same purposes as Western Hemlock, including general construction, railway ties, mine timbers,
plywood, and pulpwood.
Tsuga mertensiana is mainly important for watershed protection in the subalpine areas of the Pacific Northwest. It has been used in watershed and forest management, and to provide habitat and food for wildlife.
Tsuga mertensiana was used by the Indians much less than 7. heterophylla, presumably because of its
relative inaccessibility.
The Bella Coola tribe used parts of both species in various ways The leaves were chewed and applied to
burns, the gum was warmed and applied to cuts, and burning twigs were applied to the skin for various internal ailments.
The Thompson Indians considered Mountain Hemlock branches to be excellent material for bedding,
because the branching was so flat and the leaves were so fragrant. Diseases and Problems of Cultivation
Tsuga mertensiana is injured by a polluted atmosphere, so that it is unsuitable for planting in industrial
areas. The species is shallow-rooted, and is therefore generally considered to be susceptible to windthrow.
Dwarf Mistletoe, Arceuthobium campylopodium f. tsugensii, is a common and damaging parasite
throughout most of the range. Infection results in the formation of Witch's-brooms, spike tops, a reduction in
vigor and sometimes death.
In nature, the species may be attacked by a number of diseases and insect pests, but ornamental trees are
seldom affected if kept in good condition.
Origin of the Name
The generic name Tsuga is the Japanese common name for their native hemlocks. There is a suggestion that
it is derived from a Japanese word composed of the elements 'tree' and 'mother', meaning 'tree-mother'. The
specific epithet mertensiana commemorates Karl Heinrich Mertens (1796-1830), a German physician and
naturalist who accompanied the Russian Captain Luetke in the corvette "Senjavin" on an exploration of the
coast of Alaska between 1826 and 1829. The specific name jeffreyi honors John Jeffrey (1826-?1854), a Scottish botanist sent to the Pacific Northwest by the Edinburgh-based Oregon Committee of Men, and who collected the seed in 1851 in the Mount Baker region of Washington,
It is interesting to note that the New York Indians used the descriptive name Oh-neh-tah (pronounced Hoe-
o-na-dia or Hoe-na-dia) for the eastern species, while their name for the North Country (now Canada) was also
Hoe-na-dia, meaning "land of the trees"
The type locality for Tsuga mertensiana is "Sitka, Alaska" where it was collected in 1827 by Mertens. The
description was first published in 1832 as Pinus mertensianus by August Heinrich Custav Bongard (1786-1839),
a German Professor of Botany at St. Petersburg in Russia. It was redescribed as Tsuga mertensianus in 1867 by
Elie Abel Carriere (1818-1896) of the Museum d'Histoire Naturelle in Paris, and also director of the Jardin des
Plantes, editor of the Revue Horticole, and a life-long student of the Coniferae.
Tsuga mertensiana was first introduced to cultivation in Great Britain in 1854 by William Murray of Perthshire, who collected plants from mountains of the northwest Pacific coast for Peter Lawson & Son,
Nurserymen, Edinburgh. For a period of time, the species was known in Scotland as T. pattoniana in honor of
the Laird of the Cairnies.
Colhngwood, C.H  and W D. Brush. 1955. Knowing Your Trees  The American Forestry Association, Washington, D.C.
Dallimore, W. and A.B Jackson. 1966. 4th ed. rev. Handbook of Coniferae and Gingkoaceae. Revised by S.G. Harrison.
Edward Arnold (Publishers) Ltd., London.
Davidson, J. 1927. Conifers, Junipers and Yew: Gymnosperms of British Columbia. T. Fisher Unwin Ltd. (Ernest Benn Ltd.),
Fordham, A.J. and L.J. Spraker. 1977. Propagation Manual of Selected Gymnosperms. Arnoldia 37:1-88.
Hitchcock, C.L. et al. 1969. Vascular Plants of the Pacific Northwest. Part 1. Vascular Cryptogams, Gymnosperms and
Monocotyledons. University of Washington Press, Seattle.
Hosie, RC. 1969. 7th ed. rev. Native Trees of Canada. Canadian Forestry Service, Department of Fisheries and Forestry.
Queen's Printer, Ottawa.
Meagher, M.D. 1976. Studies of variation in hemlock (Tsuga) populations and individuals from southern British Columbia.
Ph.D. Thesis, University of British Columbia.
den Ouden, P. 1965. Manual of Cultivated Conifers. Martinus Nijhoff, The Hague.
Sudworth, C.B. 1908. Forest Trees of the Pacific Slope. Republished in 1967 by Dover Publications Inc., NY. Taylor, R.J 1972. The relationship and origin of Tsuga heterophylla and Tsuga mertensiana based on phytochemical and
morphological interpretations Amer J   Bot. 59:149-157.
Taylor, R.L and B MacBryde 1977. Vascular Plants of British Columbia: A descriptive resource inventory. Technical
Bulletin No. 4, The Botanical Garden of the University of British Columbia. University of British Columbia Press,
Vancouver, B C.
U.S.D.A., Forest Service. 1965. Silvics of Forest Trees of the United States. US D.A, Forest Service, Agriculture Handbook
No. 271.
 1974. Seeds of Woody Plants of the United States. U S D A., Forest Service, Agriculture Handbook No. 450.
Viereck, LA. and E.S. Little, Jr. 1972. Alaska Trees and Shrubs. U.S.D.A., Forest Service, Agriculture Handbook No. 410.
Welch, H.J. 1979. Manual of Dwarf Conifers, Theophrastus Publishers, N.Y.
Book Review
Harkness, Jack. 1978. Roses. J.M. Dent & Sons Ltd., Aldine House, Albemarle Street, London 290 pp + 32 color plates.
This is an excellent new addition to books on Roses, with information on all the species and Old-fashioned
Shrub Roses. For each rose, there is a description of the flower, growing habits, information on culture and
propagation, and suggested placement in the garden for best results.
The arrangement is somewhat unusual in that the author has put the whole genus in its natural order, inserting the hybrids of the thirteen groups of wild roses where they seem to belong. Thus, the chapters have
headings such as "Platyrhodon and Hybrids", the species being R. roxburghii, and "Indicae and Hybrids", or
R. chinensis. its varieties and hybrids.
The first three chapters of the book are "What is a Rose", "How Roses Are Made and Grown", and "Introducing What Follows", which includes a bibliography of rose books. Following the 14 chapters on species
and their hybrids are 5 chapters providing tables of roses to be used for specific purposes, such as height, color, flowering time, perfume, and hip production.
This book, with its 32 color plates and 12 line drawings, is a very desirable reference for the more advanced
rose grower. It is, however, somewhat technical for the novice rosarian, who requires straightforward, basic
information on planting, pruning and pest control. A more condensed, cheaper and easier-to-use book for the
novice would be "Be Your Own Rose Expert" by D.G. Hessayon and Harry Wheatcroft.
Harold (Jack) Duff ill
UBC Botanical Garden Index Seminum
The Index Seminum, or Seed List, is published annually in mid-winter, and is the means by which The
Botanical Garden offers seed for exchange with other botanical gardens and research institutions. Many
botanical gardens, including ourselves, confine their Index Semina mainly to the seeds of native plants, most
of which are collected in the wild during the previous summer and fall.
The Index Seminum for the 1979 collection year was distributed to a total of 525 institutions or individuals
engaged in research projects in 48 different countries. The list contained 387 taxa in 68 families. We received
requests for 10,135 seed packets from 370 institutions in 36 countries, of which we were able to supply 6,813
packets (67.2%). The ten most frequently requested taxa were:- Tsuga mertensiana (112 requests), Douglasia
montana (95), Darlingtonia californica (94), Mahonia repens (87), Kalmiopsis leachiana (86), Pinus monticola
(86), Primula mistissinica (85), Fritillaria camschatcensis (82), Kalmia microphylla subsp. occidentalis (81), and
Cornus nuttallii (80). The following are the ten countries in which our seed was in most demand:- United
Kingdom (49 requests), West Germany (34), Czechoslovakia (30), U.S.A (29), France (21), U.S.S.R. (19), East
Germany (17), Canada (16), Hungary (16), and Poland (14).
We acknowledge with gratitude the assistance received from members of the 'Friends of the Garden' who
spent many long hours cleaning seed, and dispatching orders.
During 1980 we received Index Semina from 313 sources in 46 countries. We requested 694 packets of seed
from these lists and have received 550 packets (79.2% of what we requested).
Donations to The Botanical Garden
The following people or organizations have donated money or gifts in kind to The Botanical Garden during
1980. We are very grateful to them, and take pleasure in listing their names here.
Mrs. Anne E. Aikins, Vancouver, B.C.
Alpine Garden Club of B.C., Vancouver, B.C.
Mr. Don Armstrong, Vancouver, B.C.
Mrs. Elsje Armstrong, Vancouver, B.C.
Dr. Kay Beamish, Vancouver, B.C.
Mr. Heinz Berger, West Vancouver, B.C.
Miss Josephine Carney, Vancouver, B.C.
Mrs  Amelie Eschauzier, Vancouver, B.C.
Mrs. Mariette Fisscher, Delta, B.C.
Ms. E. Fockler, Vancouver, B.C.
Mr. Peter Foster, Vancouver, B.C.
Friends of the Garden, UBC, Vancouver, B C.
Ms. Patricia Garth, Victoria, B.C
Mrs Maryke G. Gilmore, Vancouver, B.C.
Dr. Paul C. Gilmore, Vancouver, B.C.
Mrs. Lori Grim, Vancouver, B.C.
Dr. Basil Ho Yuen, Vancouver, B.C.
Mr. D. Kerkham, Vancouver, B.C.
Mr. Phil Makortoff, Vancouver, B.C.
Mrs. Nellie McKay, Sicamous, B.C.
Mr. Peter McKenna, North Vancouver, B.C.
Ms. Susan McLarty, Vancouver, B.C.
Ms. Marilyn Nix, Vancouver, B.C.
Mrs. Kay Pettison, Vancouver, B.C.
Mr. H. Petersen, Auckland, N.Z.
Mr. Peter V. Ruttkay, Vancouver, B.C.
Capt. Adrianus Schweitzer, West Vancouver, B.C.
Dr. William Theobald, Lawai, Kauai, Hawaii
Tuscany House Fine Interiors, Vancouver, B.C.
Vancouver Orchid Society, Vancouver, B.C.
Mr. Henk F. Vanderhorst, Vancouver, B.C.
Dr. H.J. Van Norden, Vancouver, B.C.
Dr. Arnold Van Stekelenburg, West Vancouver, B.C.
Dr. E.G.Q. Van Tilburg, Vancouver, B.C.
Mr. Paul Hyleco Wolsak, Vancouver, B.C
Mr. R.S. Woodward, West Vancouver, B.C.
Mrs. Linda Yip, Vancouver, B.C, 86
Botanical Garden News and Notes
Revegetat/on Program — Under a research contract funded by the B.C Ministry of Forests, a program of
research into the propagation and establishment of shrub and tree species for erosion control was directed by
Dr. Chris Marchant of The Botanical Garden. The experiments are designed to determine those B.C. native
shrubs most useful for rehabilitation of degraded soil in areas disturbed through logging operations in coastal
and interior regions of the province. Nursery trials will determine the most efficient methods of raising bulk
stocks of seedlings or cuttings for each species. Plants are being tested in increasing numbers in trial plantings
on selected field sites. Areas of operation for the program are in the Queen Charlotte Islands, the Kootenays,
and the Fraser Canyon.
NCTRH 1982 Annual Meeting — The National Council for Therapy and Rehabilitation through Horticulture
1982 Annual Meeting will be hosted by The Botanical Garden at the University of British Columbia in August,
1982. Information regarding the program can be obtained from the Office of The Botanical Garden.
Dr. Stearn Re-Visits — Dr. and Mrs. William T. Stearn recently visited The Botanical Garden. Dr. Stearn
officially dedicated the B.C. Native Garden component and the E.H. Lohbrunner Alpine Garden three years
ago. We were pleased to have Dr. Stearn and his wife re-visit The Botanical Garden to see the changes that
have taken place since they participated in the opening ceremonies.
FOG Program for Spring 1981 — "Asia in the Garden" is the theme for the 'Friends of the Garden' study and
project program for Spring 1981. This program is designed to provide basic information on the Asian component in The Botanical Garden as it will be one of the areas officially opened in May, 1981. A total of 43
members now actively participate in the Friends of the Garden program. In addition to the training program,
the Friends of the Garden now have some 17 projects to work on, ranging from the development of a revised
Bird Checklist for the Garden to the development of a tapestry, woven and dyed from natural material in
British Columbia, for the Main Garden Centre.
New Benches Installed in The Carden — A program was undertaken during the winter to install new benches
and trash containers of the Frances Andrew design throughout the Garden areas. This has long been needed
to provide a public amenity for visitors to the Garden.
Plant Introduction Scheme of The UBC Botanical Carden — A renovated program for introduction of new
plant materials to the nursery trades has been established at The Botanical Garden. This program has direct
relationship with the Long Ashton Clonal Selection Scheme in England; the Hornum Research Centre F.S.H.
Scheme in Denmark; and other private European schemes such as the Darthuizer Clonal Collection of
Holland and the Bruns Nursery Hardiness Program and Clonal Selection Evaluation of West Germany. A
special evaluation committee is being developed to initiate the program during the summer of 1981.
Members of the Botanical Garden Advisory Council for this Scheme are: Mr. Peter Jeck of Jeckway Landscaping Ltd., Burnaby, B.C.; Mr. Clive L. Justice of Justice, Webb & Vincent Landscape Architects, Vancouver,
B.C; Mr. Greg Murray of E.J. Murray & Sons, Langley, B.C.; Mr. Rick Sorenson of Homestead Nurseries,
Claybum, B.C , Mr. Frank van Hest of Art Knapp's Garden Centre, Richmond, B.C.; Mr. Joe Crocco, Executive
Director of B.C. Nursery Trades Association, Surrey, B.C.; Mr. A. Bruce Macdonald, Assistant Director,
Botanical Garden; Dr. John W. Neill, Research Scientist, Botanical Garden and Professor, Plant Science
Department, UBC; Mr. Ron Rollo, Botanical Garden; Mr. Charles Tubesing, Botanical Garden; and, Dr. Roy L.
Taylor, Director, Botanical Garden. The program is designed to provide a means of introduction for some of
the best selected material from Europe and Asia, and to provide a means of outlet for new material
developed at The Botanical Garden.
Revised Plant Info-Cram for Roses — The results of the 1980 Rose Trials at UBC Botanical Garden are now
available as a Plant Info-Gram from The Botanical Garden. Interested parties should write directly to the
Office of The Botanical Garden for this info-gram. Ten Year Climatological Summary
The Botanical Garden has copies of the weather recorded at the UBC weather reporting site since 1961.
During the last decade the measurements have become metric, and we have changed the items recorded in
the Climatological Summary table included in every issue of Davidsonia.
During the ten year period 1971-1980 the total precipitation (rain plus snow) decreased from 1976 through
1979, with a low of 1016.4 mm being recorded in 1979. The highest precipitation was in 1971, with 1517.8 mm
recorded (1265.5 mm rain and 252.3 cm snow). (It must be noted here that the main weather reporting station
for Vancouver is at the Vancouver International Airport, where 1419 mm was recorded in 1980 as the highest
ever. However, the UBC campus often receives more precipitation than the airport.) The highest snowfall in
one month was recorded in January 1971, with 102 cm falling on 6 days. Over the ten years, UBC campus
received an average of 1210.48 mm of rain on 177.6 days and 61.15 cm snow on 12.7 days each year, for a
total average annual precipitation of 1271.63 mm. Snow fell in January each year (from a low of 1.3 cm on 1
day in 1976 to the high of 102 cm in 1971) and in December of 8 years (1976 and 1979 being snowless in that
month), with a low of 1.3 cm on 1 day recorded in 1973 and a high of 87.9 cm on 16 days in 1971. Snow was
recorded in March of four years, and a trace was recorded in October of only one year (1971).
The average maximum temperature during the period ranged from a low of 4.84°C in January to a high of
20.34°C in July, while the average minimum temperature ranged from 0.07°C in January to 13.12°C in August.
The highest maximum temperature recorded in the ten years was 30°C in September of 1973, and the lowest
minimum temperature was -11.4°C in December, 1978.
The number of hours of bright sunshine averaged 1844.74 hours per year over the ten years, with a high of
2030.1 hrs in 1979 and a low of 1642.1 hrs in 1976. The maximum possible is 4390.4 hrs per year. The average
daily sunshine ranged from a low of 1.71 hrs in December to a high of 9.36 hrs in July. The dullest month on
record was December 1980 with a total of 14.5 hrs of sunshine (an average of 0.5 hrs per day). The brightest
month in ten years was July 1971 with 335.6 hrs, averaging 10.8 hrs per day (August 1967 recorded 339.1 hrs, or
10.9 hrs per day). The number of days totally overcast per month ranged from an average of 15.8 in December
to 1.7 days in July. The dullest month, December 1980, recorded 23 totally overcast days. No overcast days
were recorded for 6 months during the ten years — April 1973, May 1979, July 1975, and August 1971, 1972,
and 1973,
The only commentary that can really be made on the ten year cycle is that it has lived up to the local saying, "Vancouver has 5 days of rain and 2 of sun in winter, and 5 days of sun and 2 of rain in summer"!
As far as gardening is concerned, the last frost was recorded in April (the latest being -0.6°C on April 1,
1976, and 0°C on April 11,1972), and the first frost in October (the earl iest being -8.33°C on October 28,1971),
giving at least 5 frost-free growing months. However, grass minimum temperatures at or below 0°C have been
recorded regularly in May (8 years) and as late as June in 1976 (-0.6°C), and as early as September on four
occasions (ranging from 0°C to-4.4°C). The lowest grass minimum temperature recorded in the ten years was
Data                                          1971-1980
Average maximum temperature    (°C)
Average minimum temperature
Highest maximum temperature in 10 yrs
Lowest minimum temperature in 10 yrs
1 7
-2 2
Average rainfall (mm)
68 9
Average no days with rainfall
20 3
Average snowfall (cm)
Average no. days with snowfall
Average total precipitation (mm)
130 4
110 3
Average hours bright sunshine
71 0
53 3
Hours bright sunshine possible
Average daily sunshine (hrs)
1 7
Average no. days total overcast
Site:    The University of British Columbia, Vancouver, B.C., Canada V6T 1W5
Position: lat. 49° 15' 29" N;    long. 123° 14' 58" W.    Elevation: 104.4m -17.2°C in December 1971. During the preceding ten years, 1961-1970, the latest frost was recorded in March
of 1962 and 1970, and the earliest in November of 1963 and 1970, although 0°C was recorded in October
1970. Most gardeners in the Lower Mainland area feel confident enough to begin sowing seed outdoors late in
April and expect to pick crops well into September and October (especially when staggered planting is practised). The generally mild climate means that roses are often in bloom as late as December — providing good
photographic copy for local newspapers!
Climatological Summary for 1980*
The year 1980 will be remembered as one of the dullest and wettest on record, with 1418 mm of precipitation and 1716.5 hours of sunshine. November with 308 6 mm on 24 days was the wettest on record, and
December with only 14.5 hours of sun was the dullest ever recorded, June (78.2 mm on 16 days) was the wettest recorded for that month in 20 years. May and November had the lowest hours of sunshine (182.1 and 37.9
hours respectively) recorded for those months in 20 years at UBC. However, both November and December
had record maximum temperatures for those months (17.5°C on November 4 and 14.6°C on December 25),
but December 6 with -9.7°C was a record low for that date. Fortunately, there was a good snow cover during
the December cold period to protect against root damage, and only minimal foliar damage occurred.
For the gardener, 1980 was a bad year for annuals — petunias had little chance to bloom, and even zinnias
and marigolds, usually so good in this area, did not come up to standard All ericaceous material thrived on
the additional summer moisture, hardening off well during the good weather of early fall. Fall color on trees
and shrubs was good, although later than usual. Defoliation, however, was rapid when the heavy rains started.
The additional summer precipitation contributed to heavier than usual fall flowering of the Western Flowering Dogwood (Cornus nuttallii).
We must point out that in the table below the total precipitation since January 1 has increased by an additional 10 mm. This is due to an error in the tables received from the weather reporting station, which we did
not catch at the time.
Data                                                       1980
Average maximum temperature
Average minimum temperature
3.1 °C
Highest maximum temperature
Lowest minimum temperature
Lowest grass minimum temperature
Rainfall/no. days with rain
62.9 mm/6
308.6 mm/24
206.5 mm/23
Total rainfall since January 1, 1980
862.0 mm
1170.6 mm
1377.1 mm
Snowfall/no days with snowfall
26.3 cm/6
Total snowfall since October 1, 1980
26 3 cm  .
Hours bright sunshine/possible
Ave daily sunshine/no. days total overcast
5.3 hr/3
1.3 hr/16
0 5 hr/23
'Site: The University of British Columbia, Vancouver, B.C., Canada V6T 1W5
Position: lat. 49° 15' 29" N; long. 123° 14' 58" W. Elevation: 104.4 m
Colophon Notes for Volume 11
This volume has been printed in Oracle type on Donegal Linen Text by the Copy and Duplicating Centre,
University of British Columbia, Vancouver. The ink used was deep brown. A summer hanging basket. The plants include
(clockwise from top right): Geranium cv.;
Helichrysum petiolatum. Licorice Plant; Zebrina
pendula. Wandering Jew; Schizanthus cv.,
Butterfly Flower (in centre of basket); Campanula
isophylla, Star-of-Bethlehem, Lamiastrum
galeobdolon cv. Variegatum, Yellow Archangel;
Fuchsia cv.; and Abutilon cv. Polygonum capitatum has branches trailing to
25 cm with leaves up to 3 8 cm long. The flowers
are pink and in dense heads up to 2 cm across.
This Himalayan plant may be used in hanging
Volume    11
Number    4
Winter    1980
British Columbian Plants in Winter 65
Mixed Hanging Baskets 72
Tsuga mertensiana in British Columbia 78
Book Review 84
Index Seminum 85
Donations to The Botanical Garden 85
Botanical Carden News and Notes 86
Ten Year Climatological Summary 1971-1980 87
Climatological Summary for 1980 88
Colophon Notes for Volume 11 88


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