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Davidsonia Jun 1, 1976

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 DAVIDSONIA
VOLUME 7
NUMBER 2
Summer 1976 Cover:
Rubus parviflorus, the Thimbleberry, is a
common shrub in Pacific coastal forests.
It is a near relative of the raspberries and
blackberries, and its fruits are edible.
Ledum groenlandicum or Common Labrador
Tea is a member of the family Ericaceae.
It is readily distinguished by the rusty hairs
on the undersides of the leaves.
DAVIDSONIA
VOLUME 7 NUMBER 2 Summer 1976
Davidsonia is published quarterly by The Botanical Garden of The University of British
Columbia, Vancouver, British Columbia, Canada V6T 1W5. Annual subscription, six dollars.
Single numbers, one dollar and fifty cents. All editorial matters or information concerning
subscriptions should be addressed to The Director of The Botanical Garden.
A cknowledgements
The pen-and-ink illustrations on the front and back covers and inside covers are by Mrs.
Lesley Bohm, and those on p. 13 and pp. 19-22 are by Ms. Geraldine Guppy. Photographic
credits are as follows: p.15 (top), Mr. Art Guppy; p. 15 (others), Ms. Geraldine Guppy; p. 18,
Mr. Colin Price, courtesy of The Province; p. 23, Dr. Christopher Marchant. Editorial and
layout assistance was provided by Ms. Geraldine Guppy and Mrs. Jean Marchant.
ISSN 0045-9739 The Hawkweeds of British Columbia
GERALDINE A. GUPPY
The hawkweeds, genus Hieracium, are a group of herbaceous perennials
belonging to the Asteraceae or Aster family. They are related to Taraxacum
(the Dandelion) and to Hypochoeris (the Cat's-ear or Summer-dandelion),
both of which commonly invade Vancouver gardens.
The family Asteraceae is a large, widely distributed and highly evolved
plant family which is easily recognized by its characteristic flower heads.
Each head is a composite of numerous individual flowers, hence the
family's alternate name, the Compositae. The individual flowers are of two
types: disk flowers (with tubular corollas) and ray flowers (with strap-
shaped corollas). Flower heads made up entirely of disk flowers (as in
thistles, for example) are called discoid, those containing only ray flowers
are called ligulate, and those having flowers of both types are called radiate. The genera making up
the tribe Cichorieae (of which the hawkweeds are one) all have ligulate flower heads. A single ray
flower of Hieracium cynoglossoides is shown at left. The pappus, one of the most highly specialized
structures in the flower, aids in dispersal of the seed and is thought to be a modified, much reduced
calyx. The anthers are joined together into a tube or ring, a morphological feature which is characteristic of the family.
The genus Hieracium is a very large and complex group, particularly in the Old World where
weedy species are numerous. At a conservative estimate there are 750 species altogether, on a worldwide basis; these fall into four groups or subgenera. The first and largest of these is the subgenus
Euhieracium, containing many large and vigorous species. It is a predominantly European group,
though it also occurs on this continent. Next is the subgenus Pilosella, also native to the Old World.
The plants of this group are usually stoloniferous and often scapose (i.e., having basal leaves and a
leafless flowering stem). Third is the subgenus Stenotheca, which occurs more typically in the New
World, and last is the subgenus Mandonia, a small group of species found only at high elevations in
the Andes of South America.
The hawkweeds that are found in British Columbia come from three of these four subgenera.
There are 14 species altogether, of which half are native to the province and the remaining half are
introduced. The introduced species belong to Euhieracium (two species) or to Pilosella (five); the
native taxa belong to Euhieracium (one) or to Stenotheca (six). We will first look at the introduced
hawkweeds.
Not all introduced plant species are weeds, but a very large number of them are. Introduced plants
are plants that have established themselves in a new and foreign environment, and weeds are the ultimate example. A successful weed has a number of characteristics that are responsible for its success.
Almost all weedy plants are ready colonizers, adapted to successional or disturbed habitats. Usually
they are able to set abundant seed without the aid of a pollinator, either by self-pollination or by
special mechanisms such as apomixis (setting seed in the complete absence of pollen, by a sort of
"budding" process). Many hawkweeds, especially some of the European species, are apomictic. This
makes them independent of external factors which might otherwise restrict their success in new areas.
Weeds frequently reproduce by vegetative means and readily regenerate after vegetative damage.
Most readers are familiar with the ease and speed with which dandelions regrow after their tops have
been pulled off. Finally, a common characteristic of weeds is phenotypic (morphological) plasticity
— the ability of a given individual plant of a species, with a given genetic constitution, to develop a
growth habit suitable to the conditions in which it finds itself.
AH of the introduced hawkweeds in British Columbia are apomictic or thought to be so. They are
often annoyingly weedy, but several of them are quite showy. They are as follows: Hieracium aurantiacum Linnaeus (Orange Hawkweed). This species is an attractive plant, with a
rosette of basal leaves and a slender, usually leafless flowering stem covered with dark bristle-like
hairs. The plant produces abundant stolons. Its bright orange-red flowers are of a color rarely seen
amongst hawkweeds and unique amongst those occurring in our area. This hawkweed would make a
good garden plant if it were not so invasive. In fact, it has long been a garden flower in Europe, and
this is the reason it was introduced on this continent. It is an aggressive weed, however, and those
who are attracted by the flame-colored heads should consider carefully before allowing it into the
garden. It might well be useful as a ground cover for erosion control, where aggressiveness is an asset.
It is found quite frequently in the Vancouver area. Two or three years ago there was an attractive
small stand of it along University Boulevard on the University of British Columbia campus, but it
was gradually eliminated by repeated mowing. It has also established itself in several places in the
Interior of the province, for example the Slocan Valley. This hawkweed was probably the first
introduced species to appear in British Columbia.
Hieracium piloselloides Villars (Tall Hawkweed). This species has a compact cluster of slender basal
leaves and a long, slender flowering stem a foot or so high. The stem is topped with a cluster of yellow
flower heads. This plant somewhat resembles H. aurantiacum in general appearance but is taller and
more slender. Though it belongs to the subgenus Pilosella, it is not stoloniferous. However, it is
apomictic and sets abundant seed, so it often occurs in large stands containing many thousands of
plants. A pretty sight, providing that it is not one's own cow pasture where it has chosen to grow!
This hawkweed has established itself in vacant fields and along roadsides near a number of places in
the Interior. Among these are Hazelton, Terrace, Prince George, Nelson and portions of the
Yellowhead Highway.
Hieracium floribundum Wimmer & Grabowski (Yellow Devil Hawkweed) and H. caespitosum
Dumortier (Meadow Hawkweed). These two species are closely related to H. piloselloides, being distinguished from it by the fact that they are stoloniferous. Both are infrequently encountered in British
Columbia, but they can be expected to occur in the same type of habitat as does H. piloselloides. The
14 leaves of H. caespitosum are densely to moderately hairy, whereas those of H. floribundum are
sparsely hairy to glabrous. Apart from this the two species are very similar — so much so, that a good
case could be made for considering them as different phases of a single species. They belong to a
taxonomically difficult group of hawkweeds, however, and a final decision on their classification is
best made by European botanists.
Hieracium pilosella Linnaeus (Mouse-ear Hawkweed). This is a small, creeping plant whose leaves
are covered on the underside with a silvery wool of stellate hairs. If left to grow undisturbed it will
form a dense leafy mat. It is the only species in our area in which the flower heads almost always
occur singly. The outermost ray flowers of each flower head are often tinged with red on the outer
side, giving the plant an extra touch of color. It is an attractive though persistent little plant. It is
widely established in Ontario and eastward, but is relatively rare in British Columbia. This, of course,
may be only a temporary state of affairs.
Hieracium lachenalii Gmelin (Common Hawkweed) and H. murorum Linnaeus (Wall Hawkweed).
These are large robust plants, perhaps the most strongly growing of the introduced species found in
British Columbia. The two species are very much alike, their main difference being in leaf shape.
They have big, broad, often coarsely toothed leaves, rounded at the base in H. murorum and tapering
in H. lachenalii, and large yellow flower heads. Hieracium murorum has seldom been collected in the
province. However, H. lachenalii is very abundant along the shoulders of Highway 3 immediately
east of Hope. The proximity of the railroad may have something to do with its occurrence there,
railroads being a common means of dispersal for weed seeds.
The native hawkweeds are much more shy and retiring than the introduced species, and their
reproductive patterns are also different.. Only one of the seven native species is apomictic. Two are
somewhat weedy in appearance, but neither of these is invasive. The native taxa are as follows:
Hieracium umbellatum  Linnaeus  (Narrow-leaved  Hawkweed).  This is a tall,   large-flowered,
somewhat weedy-looking species found in fields and along roadsides in the drier regions of the o
a
o
3
15
FIGURE 1. Some of the Hieracium species occurring in British Columbia (clockwise from top): H. triste, H. piloselloides, H. scouteri and H. umbellatum. province. It differs from our other hawkweeds in that its leaves are more or less evenly distributed up
the stem, rather than clustered toward the base. The basal leaves are often dry and dead by flowering
time. This plant is also our only native apomictic species. Since apomixis is of adaptive value to
weedy species, this is consistent with the type of habitat in which this plant is found. The
Narrow-leaved Hawkweed is often attacked by a rust, which covers the leaves and stem with small
brown spots and which may become quite pronounced as the growing season progresses. However,
this organism appears to have little effect on the overall vigor of the plants.
Hieracium albiflorum Hooker (White Hawkweed). This is our only white-flowered species. The
flower heads, though numerous, are small and inconspicuous, and they usually set seed by self-
pollination. This species is common throughout the province, along roadsides and field edges, but is
seldom a troublesome weed. It is the least decorative of the hawkweeds found in British Columbia.
Hieracium albertinum Farr (Western Hawkweed), H.cynoglossoides Arvet-Touvet (Hound's-tongue
Hawkweed) and H. scouleri Hooker (Scouler's Hawkweed). These three closely related species
differ from one another only in the hairiness of their foliage, and there is good evidence for considering them varieties of a single species. The yellow flowers are quite large and showy as Hieracium
flowers go, and they produce abundant pollen. Though not spectacular, the plants are an attractive
sight in their native haunts. One good place to find them is the Botanie Valley near Lytton, B.C.
Hieracium albertinum, in particular, can be quite showy, with the long silver-white hairs on its
involucre. Far from being weedy, all three of these species are quite difficult to maintain in
cultivation, and do not like to have their roots disturbed during the flowering period. They all prefer
a dry climate, but their preferences vary slightly in degree: H. albertinum (the hairiest species) tends
to grow in the driest spots and H. scouleri (the least hairy species) in the dampest sites. It is likely that
the hairs aid in the conservation of moisture.
Hieracium gracile Hooker (Slender Hawkweed) and H. triste Willdenow ex Sprengel (Woolly
Hawkweed). The hawkweeds so far mentioned are all of low to middle elevations, whereas these two
species are alpine. They may be found at moderate to high elevations throughout the province.
It) Generally, H. gracile is the more common of the two species in the southern parts of the province,
and H. triste is more commonly found in the north. Together they have a range extending from
California to Siberia. They are inconspicuous little plants, in nature sometimes consisting of a single
small flower head on a stem 5 cm high. Often they grow singly rather than in stands. Like many small
natural objects, however, these little plants are worth a detailed inspection. The involucres and upper
stems are abundantly dotted with silvery stellate hairs, and H. triste, the more northerly species, has a
dense woolly layer of long soft gray hairs on the involucre. In many specimens these hairs exceed the
ray flowers in length. These two species display considerable phenotypic plasticity, and when grown
in the garden they may become tall plants with a hundred flower heads or more. This aids them in
adapting more readily to the harsh environment in which they live.
Key to the genus Hieracium of British Columbia
la Flower heads pale cream-color to white; involucre, stem and leaves lacking
stellate hairs   H. albiflorum
lb Flower heads yellow or orange-red; small white stellate hairs present,
especially on the involucre
2a Slender alpine species; involucre with soft gray to black villose hairs 1-5 mm
in length, often mixed with black glandular hairs and white stellate hairs;
leaves narrowly elliptical to spatulate, often obtuse, all basal except for
(sometimes) one small leaf on stem
3a Involucre lacking glandular hairs; villose hairs grayish,
generally 3-5 mm long H. triste
3b Involucre with black glandular hairs; villose hairs blackish,
generally 1-3 mm long    H. gracile
2b Plants not alpine; involucre lacking villose hairs (though sometimes
with long bristle-like hairs); leaves narrowly to broadly elliptical, acute,
often not all basal
4a Leaves densely stellate beneath; stolons present; flower heads one per
stem, yellow, the outermost ray flowers often red-tinged on the back;
plants introduced  H. pilosella 4b Leaves not densely stellate beneath; stolons present or absent; flower
heads several to many, yellow (not visibly red-tinged on the back) or
red-orange; plants introduced or native
5a Flowers red-orange (darker on drying); stolons present; plant an
introduced weed  H. aurantiacum
5b Flowers yellow; stolons present or absent; plants introduced or native
6a Leaf margins with short stiff subconic hairs; stem leafy, leaves
alike in size except for the much reduced upper ones; basal leaves
usually few or absent by flowering time; setose hairs lacking on
stem (except sometimes at very base) and on involucre H. umbellatum
6b Plants lacking subconic hairs; stem leafy or scapose, leaves
progressively reduced upward; basal leaves generally present at
flowering time; involucre and stem often with setose hairs
7a Leaves narrowly elliptical, seldom wider than 3 cm; entire or nearly so
8a Plants introduced and weedy, developing stolons by
flowering time; rhizomes usually long and slender;
setose hairs on involucre and upper stem (if present)
having blackish bases
9a Leaves moderately to densely setose on both sides,
not glaucous    H. caespitosum
9b Leaves glabrous to sparsely setose on both sides,
glaucous    H. floribundum
8b Plants native or introduced, not stoloniferous; rhizomes
shortened into a caudex; setose hairs various
10a Leaves all basal except for a single greatly reduced
leaf on the stem; setose hairs on involucre and
upper stem having blackish bases; plants
introduced and often invasive H. piloselloides
10b At least some of the cauline leaves well-developed
(though reduced in size upward); setose hairs 1 /
(if present) white; plants native, not at all invasive
11a Leaves moderately to abundantly setose on
both sides; involucre sometimes with white
setose hairs
12a Involucre covered with long white setose
hairs    H. albertinum
12b Involucre lacking setose hairs   H. cynoglossoides
lib Leaves glabrous to very sparsely setose on
both sides, often glaucous; involucre lacking
setose hairs    H. scouleri
7b Leaves broader (ovate to elliptical), sometimes purple-
blotched, often wider than 3 cm; at least some leaves broadly
toothed near the base
13a Leaf blades tapering gradually to
the base    H. lachenalii
13b Leaf blades rounded, truncate or
cordate at the base H. murorum
REFERENCES
Baker,  H. G. and G. L. Stebbins (eds). 1965. The Genetics of Colonizing Species. Academic Press, New York.
Gleason, H. A. 1963. The New Britton and Brown Illustrated Flora. Vol. III. Hafner Publishing Co. Inc., New York.
Guppy, G.A. 1975. The systematics of indigenous species of Hieracium (Asteraceae) in British Columbia. M.Sc. Thesis,
University of British Columbia.
Gustafson, A. 1946-1947. Apomixis in higher plants. Parts I-III. Acta Univ. Lund N.F. 42, 43.
Hitchcock, C. L., A. Cronquist, M. Ownbey and J. Thompson. 1955. Vascular Plants of the Pacific Northwest. Part V.
Compositae. University of Washington Press, Seattle.
Hulten, E. 1968. Flora of Alaska and Neighboring Territories. Stanford University Press, Stanford.
Stebbins, G. L. 1953. A new classification of the tribe Cichorieae, family Compositae. Madrono 12: 33-64. Fruit Tree Training for the Home Garden
DOUGLAS G. SMYTHE
18
The growing of fruit trees is one of the most satisfying forms of gardening. However, standard'
fruit trees may grow too large for the average city lot. An alternative to growing fruit in the conventional way is to adapt the plants to your location by training them. In this way they will take up less
space, and their reduced size makes routine maintenance, treatment of disease, and picking of the
fruit much easier. Various forms may be obtained by training, and each of these is better suited to
some kinds of fruit trees than others. The training of these plants need not be unduly difficult if some
basic rules are followed.
One-year-old trees must be used. These are not easily obtained in B.C. as there has been no
demand for them. The trees generally available in nurseries are two-year-old trees. However, these
are not suitable for training, and an effort should be made to obtain one-year-old stock if at all
possible. Use certified virus-tested stock. A number of reputable nurseries in the Greater Vancouver
area sell virus-free material. Dwarfing understocks should be used for all fruit trees for which they
are available, otherwise difficulties will be encountered in maintaining the size and shape of the tree.
FIGURE 2. Mr. Ken Wilson with a group of
cordoned apple trees being grown at the
Botanical Garden. FIGURE 3. A cordon, shown (left to right) at
time of planting; the first summer after planting; the second summer after planting; at
maturity.
Ss
J
r
Plant the young trees during their dormant period, November to March, whenever weather
conditions permit. The form in which they are to be trained should be decided on before planting, so
that a suitable location can be prepared and (where necessary) a supporting framework built.
Apples and Pears
For both apples and pears a dwarfing rootstock should be used. The smallest dwarf stock
available for apples is M-9, but this understock has poor root development and the tree must be
staked from the time it is very young. The rootstock M-26, which produces trees almost as small, is
much used in western Canada but also may need staking. Other less dwarf rootstocks that are suitable
for training are also available in B.C. These include M-7, MM-106, MM-111, and even the relatively
vigorous M-2, which may be used in areas where the soil is poor. For pears, Quince C (moderately
dwarfing) and Quince A (semi-vigorous) rootstocks are best.
Apples and pears may be trained as cordons, espaliers or pyramid trees.
19
Cordons
A cordon tree consists, essentially of a single main stem on which the side branches are pruned
back to fruiting spurs. Cordons may also be grown with multiple stems. The main stem is allowed to
grow to whatever height is desired, usually 2.5 to 3 m, then pruned back to maintain it at this height.
Single cordons are usually grown at an angle of 45° (see Figure 2) in order to get the maximum length
of stem into a given height. However, they may be also be grown vertically. Multiple cordons are
more difficult to train and require more space than single cordons, but they may be grown by those
who wish to take on the challenge.
A permanent system of wiring is necessary for growing cordons. Posts of iron, concrete or treated
wood may be placed 3.5 m apart, and should extend 2.5 m above the ground. Three parallel wires are
then stretched tightly between the posts, and fastened with adjustable straining bolts. The bottom
wire should be about 75 cm above the ground, with the other wires at 50-60 cm intervals. Bamboo
canes 2.5 to 3.5 m long are attached to the wires so that the cordons may be trained along them.
For single cordons the trees should be planted slightly less than 1 m apart. If they are to be trained
as oblique cordons they should be set at an angle of 45° to the ground. The graft must be about 15 cm
above soil level, with the scion uppermost. If the tree is planted with the point of union at or below
ground level, rooting will eventually occur above the graft and the dwarfing effect of the understock
will be lost. The plants are then tied to their supporting canes with soft string. At the time of planting, FIGURE 4. An espalier, shown (left to right) at time of planting; the first summer after planting; the next spring before growth starts; the second summer after planting.
side shoots more than 10 cm long should be cut back to three buds. After this only summer pruning
should be necessary; this is usually done in late July. A good system of summer pruning (based on the
method known as the "Modified Lorette System") consists of cutting back all mature lateral shoots
from the main stem to three leaves beyond the basal cluster. Side shoots from these laterals are then
cut back to one leaf. If there are a few immature shoots, treat them in the same way as the side
shoots. The main stem is allowed to elongate until it reaches the desired height. If it is an oblique
cordon, the new growth must be tied in each year to keep it at the proper angle. Once the leader has
reached the required length, it should be pruned back each year in May. The training process for
cordons is illustrated in Figure 3.
To make a double cordon, cut back the young tree to about 30 cm above ground level, just above a
O r\ bud. Two shoots are allowed to grow, one on either side of the stem. Each of these is trained horizon-
tally for 15 cm, then grown vertically. Pruning of the two stems is subsequently carried out in the
same manner as for single cordons.
Espaliers
Espaliered trees (see Figure 4) are trained so that the branches lie in a single plane. They should be
grown against a supporting fence or wall. Many kinds of woody plants may be trained as espaliers
and there are a number of variations on the basic design. The form traditionally used for apples and
pears consists of a single main stem, with the branches extending out horizontally on either side.
If several espaliers are to be grown, the trees should be planted 3 to 6 m apart. The exact spacing
depends upon the final size of the tree, which will be regulated by the particular understock on which
it is grown.
For training and support, the branches are tied to wires stretched horizontally on the wall or fence.
There should be a wire for each tier of branches on the finished tree. The tiers are approximately
30 cm apart. During the first winter after planting the tree, cut it back to a good bud about 5 cm
above the bottom wire. There must also be two other good buds near the wire, one on the left and one
on the right hand side of the stem. Growth from these buds will produce the first tier of branches.
Allow the top bud to grow vertically, training it against a cane. Remove any buds other than these
three. During the following summer, tie the two new side shoots to canes which are arranged at a 45°
angle to the main stem. If one becomes more vigorous than the other, raise the weaker shoot to a
more vertical position. During the next winter, lower the canes and shoots, securing them to the
bottom wire. Side shoots from these main laterals are cut back to 10 or 12 cm. As the leader continues
to elongate, repeat the above process at each wire until the top wire is reached. At this point the leader
is removed and only two buds are left. The growing tips of each lateral branch should not be pruned
unless they have made poor growth. If this is the case, they should be winter-pruned to stimulate new
growth. This is done by cutting back the previous summer's growth by one-quarter. When the FIGURE 5. A pyramid apple or pear tree,
shown (left to right) in the early spring soon
after planting; in the following winter; in the
second winter.
branches of each tier have reached the desired length, the leaders should be pruned back to 1 cm of
new growth each May. The sub-laterals (side shoots from the lateral branches) are pruned back to one
leaf in the same way as described for cordons.
Pyramid Trees
These trees (see figure 5) have a central main stem from which side branches radiate outwards, the
general shape being very much like that of a Christmas tree. This training method gives a more
natural, less stylized form than those already discussed. Most kinds of fruit trees may be trained as
pyramids. A dwarfing rootstock should be used, but it should have a sturdy rooting system so that
the tree will not have to be staked.
The tree is planted during the winter but pruning is started in the spring, just before new growth
begins. At this time, the leader should be cut back to 50 cm above the ground and the side shoots back
to about five buds. During the following winter, shorten the leader back to 20 or 25 cm of new
growth. Cut the lateral branches back to a bud on the lower side, so that the branches will grow out at
a wide angle. During the latter part of July each year, prune the main branches back to 5 or 6 leaves
and cut out any competing central leader. Each winter the central leader should be pruned back to 20
or 25 cm of new growth, and any secondary growth that has appeared since the summer should be cut
back to one good bud. Any thinning out of branches should also be done at this time. Once the tree
has attained a height of 2 m, prune the new growth hard back every May to a length of about 1 cm in
order to keep the tree to the required height.
Peaches, Apricots, Plums and Cherries
For peaches and plums, a good rootstock is the semi-dwarfing St. Julien A. In the case of
peaches, since they are not exceptionally large trees, ordinary vigorous stock could also be used. No
dwarfing stock is available for apricots or for sweet cherries, so if these trees are to be trained a large
amount of space must be allowed. Sour cherries, however, have a less vigorous growth habit and
produce smaller trees.
These trees are suitable for training as fans or as pyramids.
Fan Training
Fan training (see Figure 6) is the best method to adopt with trees which are to be planted against a
south- or west-facing wall or fence. The branches are all in one plane, and are trained to radiate out
from the tree starting a short distance above the ground. This allows each branch the maximum
amount of light and air.
Plums and peaches on semi-dwarfing rootstock, as well as sour cherries, should be planted 4.5 to
5.5 m apart if more than one tree is being planted. Apricots, sweet cherries, and peaches on a vigorous
rootstock should be planted 5.5 to 7.5 m apart if more than one is to be planted. For most city gardens, a single tree will suffice. It should be kept in mind, however, that both sweet cherries and plums
21 FIGURE 6. A fan-trained tree, shown (left to right) at time of planting; the first summer after planting; the following winter; the second summer after planting;
at maturity.
22
must be cross-pollinated. This is achieved usually by growing another tree of a compatible variety
nearby (possibly in the neighbour's garden!) Another solution to this problem is to graft onto your
tree a branch from a different variety.
Plant the one-year-old trees 15 to 25 cm away from the wall or fence against which they are to
grow, sloping the stems slightly towards it. Training wires to which the branches can be attached
should be stretched horizontally on the wall, about 15 cm apart.
During the first spring after planting, cut the tree back to 60 cm above the ground, preferably to a
lateral branch or a good bud which has a couple of other buds below it. All other laterals should be
removed. In the following summer select two good shoots, one on either side, about 30 cm above the
ground. Remove all buds except those at the top of the stem and on the lateral shoots themselves.
When the two side shoots have reached 45 cm in length, tie them to canes at approximately a 45°
angle. The main stem above these shoots may then be cut out and the wound treated with a tree paint.
The next February, cut back each of the two shoots to a bud 30 to 45 cm from the main stem. During
the second summer after planting, allow the shoots from these end buds to grow, and tie them in as
before. In addition, two well-placed shoots on the upper side and one on the lower side of each
branch should be allowed to grow on, and should also be tied in; this gives a total of eight branches.
During February of the third year, cut back each of the branches to leave about 50 cm of ripened
wood from the previous summer.
Space permitting, repeat this summer and winter pruning for one more year. Once the final size of
the tree has been attained, the only operations that need to be carried out are the pinching back of
unwanted shoots to about four leaves, and the removal of those that would otherwise compete with
fruiting wood. When needed, well-placed buds may be allowed to develop in order to produce replacement shoots. These operations should be done during the summer months, starting at the top of
the tree and working down it, and spreading the work over a period of one to two weeks.
Pyramids
Plums are commonly trained as pyramid trees. Peaches and sour cherries may also be grown in
this fashion, though this is less usual. Plants grown on a dwarfing rootstock should be used whenever
obtainable. The basic method of training is somewhat similar to that for apples and pears. At the time
of planting, cut back the leader to 1.5 m above the ground and reduce the side shoots to half their
length. Remove any side shoots within 45 cm of the ground. The following summer, during late July,
shorten the new growth to 20 cm in length. Cut it back to a bud on the lower side of the shoot, in the
same way as for apples and pears. Sub-laterals should be pruned back to 15 cm. Do not prune the
central leader until the following winter, at which time the previous year's growth should be reduced
by two-thirds. Once the tree has reached a height of 2.5 to 3 m, prune the new growth back each May
to a length of about 2 cm. During the third week of July each year, prune in the same manner as
for apples. Botanical Garden Staff
Director
Dr. Roy L. Taylor
Supervisor of Operations
Mr. Kenneth Wilson
Research Scientist (Cytogenetics)
Dr. Christopher J. Marchant
Research Scientist (Horticulture)
Dr. John W. Neill
Research Technicians
Miss Andrea M. Adamovich
Mrs. Sylvia Taylor
Secretary to the Office
V            sp/A
Miss Ellen O. Campbell
mm
Plant Accession System
Mrs. Annie Y. M. Cheng
V } vJkW s——~
Mrs. Marie Shaflik
V    ^      Jfw<l£-'C-;;w4'li<''>K2j
Education Coordinator
^~^-^l Vw«f- 'V^SS^
Mr. David A. Tarrant
y ■ v, ^?\ \ v
Horticulturists
^--^sxij^v..;) ></l A |
Mr. A. James MacPhail (Alpine Garden)
/^^giSfe^se^       lO*
Mr. Gordon J. Ramsdale (Nursery)
Gardeners
Mr. Pierre Rykuiter
rv        ) j*r^ rf*^ J
(Area Manager, South Campus)
Mr. Helmut Koblischke
(          ^. s* $v   r
(Area Manager, Upper Campus)
\    / "U-*JJ--'    Y^
Miss Margaret E. Coxon
Mr. Harold Duffill
Mr. Leonard Gibbs
vM
Mr. Robert E. Kantymir
\ a
Mr. Murray J. Kereluk
j ^*^i
Mr. Paul Kupec
('    1   s 1   \ ,./—^vsf
Mrs. Bodil Leamy
S/A \ \ '^>,
Mrs. Elaine V. Le Marquand
Miss Elaine F. Mascali
Mr. Sam M. Oyama
Mr. Ronald S. Rollo
Mr. Allan A. Rose
Mr. Douglas G. Smythe
/
Mr. Isao Watanabe
Mr. Peter A. Wharton
Mr. Thomas R. Wheeler
Mimulus lewisii, one of our most
Flora of British Columbia Program
brightly colored monkeyflowers.
Dr. Roy L. Taylor (Editor)
It is common in damp alpine
Ms. Geraldine A. Guppy (Research Assistant)
meadows in midsummer.
Research Associates
Dr. Charles E. Beil
Dr. L. Keith Wade Nuphar tutea ssp. polysepala, the Yellow
Pond Lily. This vigorous water lily is
widespread in British Columbia wherever
suitable habitats occur.
Volume 7
Number 2
DAVIDSONIA
Summer 1976
Contents
The Hawkweeds of British Columbia    13
Fruit Tree Training for the Home Garden    18
A Rhododendron Phenology Study Program   23
Local Initiatives Program 1975-76   24
Climatology   24

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