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Davidsonia Jun 1, 1973

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 DAVIDSONIA
VOLUME 4        NUMBER 2
Summer 1973
RHODODENDRONS ON CAMPUS Cover
A portion of the Tantalus Range with
the left flank of Black Mountain in the right
foreground. One of the many vistas
seen from the Point Grey Campus.
DAVIDSONIA
VOLUME 4        NUMBER 2        Summer 1973
Davidsonia is published quarterly by The Botanical Garden of The University of British
Columbia, Vancouver, British Columbia, Canada V6T 1W5. Annual subscription, four
dollars. Single numbers, one dollar. All editorial matters or information concerning subscriptions should be addressed to the Director of The Botanical Garden.
A cknowledgements
Cover drawings and vignettes are by Mrs. Lesley Bohm. Photographic credits are as
follows: Black-and-white—pages 11, 25, C. J. Marchant; page 23, R. L. Taylor; pages
13, 26, R. D. Turner. Colour—all R. D. Turner except page 19, figs. 1 and 4 and page 21,
figs. 5 and 6 by R. L. Taylor.
Special acknowledgement is given to The Leon and Thea Koerner Foundation for a grant
to provide assistance in defraying the cost of colour work in this issue. Introduction to the
Rhododendrons on Campus
ROY L. TAYLOR
I suppose there is no other single plant on the campus at The University of British Columbia that people
view with more delight each year than the genus Rhododendron. Rhododendrons represent the most widely
used landscape plant on the campus, and a rich mixture of both species rhododendrons and hybrid rhododendrons are to be found in nearly every corner. The use of rhododendrons as important landscape elements
at The University of British Columbia goes back some 25 years to the immediate post-war period after
World War II. A major development of the campus at the University took place at that time. At the same
period that the physical development occurred, considerable care was taken to provide the students, staff
and the visitor with a pleasant landscaped environment. Rhododendrons played an important part in providing this environment. Prior to World War II f^ew rhododendrons could be found on the campus. An
exception were a few R. 'Cunningham's White' (arboreum f. album X caucasicum) planted near the
Geography Building (the old Applied Science Building).
One of the principal areas of focus of interest in the genus on the campus can be found near Crescent
Road and the Triangle area east of the Faculty Club and Rose Garden complex. It is in this area that the
rhododendrons, many of them fine specimens of species from the Royston Nurseries on Vancouver Island,
can be seen. These rhododendrons form the principal understorey shrub in small pockets of native west
coast conifers, and appear to be completely at home and naturalized in that environment. Such plantings
clearly indicate how well-suited the west coast conditions are for the culture of rhododendrons. From March
through June it is always a delight to wander through this area and see rhododendrons growing at their best.
A mass planting of rhododendrons can be found near the bus stop on Crescent Road. These plants, origin-
Rhododendron vernicosum, a variable member of the Fortunei subseries
of series Fortunei. A native of Yunnan and Szechwan occurring between
9,000 and 14,000 feet elevation. A plant of good form very suitable
for understorey plantings and as a specimen shrub in the larger home garden.
11 12
ally placed in this region by Dr. John Neill, are Rhododendron calendulaceum (s. Azalea, ss. Luteum)1
seedlings grown originally from material obtained from the international seed exchange. These azaleas
are most colorful in their various tones of yellows, oranges and reds in the spring, and in the fall present a
similar kaleidoscope with the coloration of leaves from russet to dark red and golden yellow. The spring
show of rhododendrons in this area is enhanced by a collection of daffodils that are found in the Triangle
area.
Other areas contain special collections of rhododendrons, and I suppose one of the most enjoyable walks
on the campus to see rhododendrons is that taken through the very pleasant surroundings of the Place
Vanier Residence complex. It is in this region that the rhododendron is used to best advantage, both in mass
plantings and as specimens, combined with some unusual tree specimens and ground cover arrangements.
Some of our best hybrid specimens can be seen in this general area. There has been a constant attempt to
provide a progression of form and texture and a succession of bloom by massing low, medium and tall
forms, representing a variety of leaf shapes and sizes, in large free form beds under the native conifers.
Perhaps the single best example of this landscape form is seen in the gardens of the president's residence.
Particular attention was given to the development of transition plantings linking formal free form gardens
with the surrounding natural woodland.
Large showy beds of both species and hybrids can be found in and around the Buchanan Building complex. Two striking beds of the red-flowered species; Rhododendron yunnanense (s. Trifiorum, ss. Yunna-
nense) and R. davidsonianum (s. Trifiorum, ss. Yunnanense), respectively, can be seen on the west side
of the building. Two mass plantings of Rhododendron fortunei (s. and ss. Fortunei) and R. decorum (s. and
ss. Fortunei) are found at the northwest corner near the entrance of the plaza. In addition to the plantings
already mentioned a list of other plantings in the vicinity of this building illustrates the diversity of both
species and hybrids used in landscaping at UBC: A. Species; R. indicum (s. Azalea, ss. Obtusum), R.
occidentale (s. Azalea, ss. Luteum), R. racemosum (s. Scabrifolium), R. augustinii (s. Trifiorum, ss.
Augustinii), R. catawbiense 'Grandiflorum' (s. Ponticum, ss. Ponticum); B. Hybrids; R. 'Elizabeth' (for-
restii var. repens X griersonianum)-, R. 'Coral Bells' (known as 'Kirin', a Kurume X kaempferi hybrid),
R. 'Sea Shell' (Kurume X kaempferi hybrid), R. 'Kathleen' (a Malvatica X kaempferi hybrid), R. 'Blue
Tit' (impeditum X augustinii), R. 'Johann Sebastian Bach' (a Kurume X mollis hybrid), R. 'Lilac Time'
(diaprepes X 'Purple Splendour'), R. 'Cynthia' (catawbiense X griffithianum), R. 'Lady Primrose' (cam-
pylocarpum hybrid), R. 'C. B. Van Nes' ('Princess Juliana' X 'Florence Smith'), R. 'America' (parentage
unknown), R. 'Louis Pasteur' (parentage unknown), R. 'Loder's White' (arboreum var. album X griffithianum), R. 'English Roseum' (a form of the catawbiense hybrid, 'Roseum Elegans').
Some of the largest rhododendrons are found in the areas already discussed, however, a specimen of
Rhododendron 'Caractacus' (a catawbiense hybrid known as one of the ironclads), found on the east side
of the old Arts Building, is nearly 20 feet in height. The largest azaleas, reaching more than ten feet in
height, are found in the naturalistic shrub corner of the Main Library frontage, north of the Chemistry
Building. Included here are the fragrant R. luteum (s. Azalea, ss. Luteum) which colors well in the fall
season.
Rhododendrons are occasionally used in special circumstances such as the R. kaempferi hybrids (s.
Azalea, ss. Obtusum) in the landscaped portions of the Nitobe Memorial Garden. These specimens provide
soft patches of color in the garden during the spring and summer seasons.
Future landscape development at The University of British Columbia will continue to utilize rhododendrons as a major part of the development program. Recent plantings in the South Campus have emphasized
the use of azaleas for roadside verge plantings. As the playing fields and the extensive, but ugly, parking lot
areas become landscaped, it is our hope that rhododendrons may well play again a significant role in providing both beauty as well as protection for the casual visitor and user of such facilities.
One of the real attributes of rhododendrons which is often overlooked is their very fine evergreen foliage.
Some superb mosaic leaf patterns are found in areas where several types of rhododendrons have been
planted along with other vegetation. Since much of our winter time in the Vancouver area is spent in rather
gray, wet days, the consideration of the details of the green vegetation is an important one in the development of any landscape planning. It is our hope that through the development of the many new species and
forms being accumulated in our species collection, new and interesting leaf forms as well as flowering
forms of the genus can be added to our already fine collection of rhododendrons on the U.B.C. campus.
!The series and subseries according to The Rhododendron Handbook, Part One: Rhododendron Species in General
Cultivation published by The Royal Horticultural Society in 1967.
-parentage of hybrids are given in parentheses. The display bed on the northwest side of the Frederic
Wood Theatre featuring Rhododendron 'Cilpinense'
(ciliatum X moupinense). The plants often flower in late
February and March providing a complimentary splash
of colour with the early spring bulbs.
Evaluation and inventory record taking in the permanent
collection of rhododendron species in the nursery.
Mr. James MacPhail (left), and Mr. James O'Friel
(right) checking record forms produced by the
computer program BGAS. Rhododendron Species
—A Developing Collection at U.B.C.
ROY L. TAYLOR
In the development of the Botanical Garden program, emphases were placed on three objectives: 1)
research, 2) education and 3) public information. In order to achieve any of these three objectives it is
necessary to develop core collections of plant groups. A prime example is the Rhododendron Species Collection being developed at U.B.C. Its development is designed to meet the three objectives of the Botanical
Garden program entitled ''Plants and Man". The decision has to be made regarding the development of
any plant collection as to the parameters of the collection. Clearly, a botanical garden cannot amass collections of all plants from throughout the world. This is not only impossible to achieve but is not necessarily
a desired objective. The genus rhododendron is valuable in having special interest to both researchers and
the public at large in the coastal region of western North America, as the climate is conducive to the propagation and maintenance of a major portion of the types of rhododendrons found throughout the world. The
very tender members of the tropical sections, such as Vireya, must be grown under glass house conditions.
In addition, many of the large-leaved species belonging to the section Falconeri must have some protection,
but a number can be grown with some degree of success although there is often damage during particularly severe winters.
14 In the reorganization of the Botanical Garden and the development of the objectives for our "Plants and
Man" program, consideration was given to the parameters of the rhododendron collection to be developed
at U.B.C. After considerable investigation and deliberation it was decided to restrict our collection in the
Botanical Garden to rhododendron species. Hybrids will be used extensively for ornamental plantings on
the campus but will be the primary responsibility of the Department of Physical Plant and their nursery
operation, which is designed to supply landscape and maintenance material for the campus ornamental
plantings. As a result of this decision an area was established in the new Botanical Garden nursery and
was developed for the establishment of a permanent collection of rhododendron species. This specific planting was inaugurated on September 27, 1971 when Dr. Douglas M. Henderson, Regius Keeper of the Royal
Botanic Garden of Edinburgh, planted the first rhododendron in the new site (see DAVIDSONIA, Vol.
2(3):29-30).
The Rhododendron Species Collection was initiated back in the early 1950's by Dr. T. M. C. Taylor and
Dr. J. W. Neill, when plans were made to bring a major collection of plants from Royston Nursery on
Vancouver Island to the U.B.C. campus. The initial collection of 1,000 rhododendrons donated by the
owners of Royston Nurseries, Mr. and Mrs. T. E. Greig, served as the nucleus of the permanent collection
of rhododendrons at U.B.C. In 1964 the University cooperated with the new Rhododendron Species
Foundation, of Eugene, Oregon, in serving as the principal propagator of the plant material that was being
obtained by the Foundation from the major gardens in Great Britain. This cooperative program has continued to the present time and has become more active in the last several years. Mr. P. H. Brydon has
become the Secretary of the Rhododendron Species Foundation, and has established a permanent home
for the collection at Salem, Oregon. An active interchange of materials has taken place between the Foundation collection and our own collection.
In 1971 and 1972 the University Botanical Garden initiated a more active acquisition program through
the help of the Vancouver Chapter of the American Rhododendron Society, who provided a grant to assist
in the development of the species collection. In addition, a grant from the Stanley Smith Horticultural
Trust was instrumental in assisting the purchase and movement of dwarf rhododendrons suitable for rock
garden development from private local collections. Mr. Ken Wilson, of the Botanical Garden staff, spent
considerable time in Britain developing additional contacts for exchange of materials and an active aquisi-
tion program of original material has been achieved through participation of the Botanical Garden in
several international plant collecting expeditions. The interest and enthusiasm by both the Vancouver
Chapter of the American Rhododendron Society and rhododendron buffs in The Alpine Garden Society of British Columbia have served to add some unusual and interesting material to our collection. Mr. James
MacPhail, of our staff, has developed over the past year a specialized peat bed garden adjacent to the
rhododendron species collection which is now being used to cultivate some of the peat-loving species.
The current species collection at U.B.C. consists of 269 species with an additional 110 infraspecific forms
or varieties of special merit. The total collection that has been established in permanent plantings is now
more than 2500 plants. In addition, an active program of propagation of plant materials from not only the
permanent collection in the Nursery but also particularly good forms of species in the general campus collection has been initiated. This program is designed to provide additional material for testing and evaluation and for dissemination to growers through the Vancouver Chapter of the American Rhododendron
Society. The basic aim of the collection is to provide a major gene pool of rhododendron species on which
research, testing, evaluation and propagation of materials can be achieved.
The Botanical Garden initiated in 1972 a program of evaluation of the species in the collection. This
evaluation consists of a five-page format designed to provide such information as the age of plant, origin
of the material, type of propagation, description of the site, record of weather conditions, indication of
weather damage, time of flowering and suitability for the home garden (see form below). In addition to
these general characteristics, the morphology of each plant is evaluated. An extensive series of measurements and characteristics are taken for each plant. A sample form and the guide for the contributor to the
development of rhododendron species records can be obtained by contacting the Botanical Garden office.
It is our hope that with an annual evaluation of the rhododendrons in our collection, pertinent information
for use by breeders and by the home gardener will be developed and a greater appreciation and use of
rhododendron species will be made. Of particular importance to the plant breeder will be the developing
inventory of morphological characters that will be desirable in future breeding programs.
The permanent collection in the Botanical Garden Nursery is arranged according to the Rhododendron
Handbook published by The Rhododendron Horticultural Society. Mass planting of species propagated from
the collection will be established in the Marine Drive Garden component of the main display gardens. This
is a long-term and continuing project but a good start has been made toward the development of material
for this display. Continued efforts will be made to obtain species material of excellent quality for incorporation into the collection at U.B.C.
UBC EVALUATION PROGRAM FOR RHODODENDRON SPECIES—1973
Observer's initials:	
NAME:
Species	
Subspecies or variety	
Cultivar	
Special form	
SERIES/SUBSERIES	
AGE ORIGIN OF MATERIAL	
PROPAGATION (check one)
seed cuttings understock graft type	
SITE DESCRIPTION (check one in each column)
open northern exposure peat	
semi-shade eastern exposure loam ,
full-shade southern exposure gravel	
western exposure	
WEATHER CONDITIONS
General winter conditions	
Lowest winter temperatures jdate	
WINTER DAMAGE (indicate 1, 2 or 3 - 3 indicates complete kill)
stem leaf bud	
FLOWERING
First date Last date Second flowering	
SUITABILITY FOR HOME GARDEN (rate 1 - 5, 5 indicates most suitable)
(check only those applicable) Rating
General garden planting   	
Mass or background planting   	
Patio or enclosed planting   	
Container planting   	
Specimen shrub or tree   	
15 Se^yfB
-J^~i^
L> Phytophthora Root Rot
of Rhododendrons
CHRISTOPHER J. MARCHANT
Many growers of rhododendrons in home gardens may not know of the existence of a very widespread
and destructive disease which can attack and kill their plants. Furthermore, it may not be widely appreciated how almost impossible it is to eradicate the disease when once it appears. Prevention is certainly
better than the cure. The disease is known as Phytophthora Root Rot or Wilt and is first noticed as wilted,
drooping leaves on the twigs.
Botanically the genus Phytophthora is a fungus very much associated with water or wet conditions. Its
life cycle is tailored to a semi-aquatic environment and this is why the disease is prevalent in wet soils and
in wet summer seasons. In some species the thread-like fungal hyphae growing near the soil surface will,
when ready to reproduce, grow vesicles at the ends of the hyphae. When these zoosporangia, as the vesicles
are called, are mature they become detached and if they come in contact with sufficient soil water they
burst open, releasing small motile zoospores. These single-celled spores, each with two hairlike flagellae,
can swim around in the wet soil thus bringing them in contact with Rhododendron roots. If spores get
into drainage or flood water, dispersal can be over long distances.
Usually the spores encyst and rest for a while after swimming. They then germinate into fungal hyphae
which attack the adjacent roots of the host plant, entering and passing through the cells and rapidly killing
the tissues.
In other species sporangia are produced aerially on hyphae which protrude through the epidermis of
the plant. Wind then carries the zoosporangia to wet soil.
The life cycle is such that the fungus does not rely on the presence of host plants to survive. Many
Phytophthora species can survive saprophytically for a while on decaying soil humus and, of course, en- 1/
cysted zoospores can survive a long time under unfavourable conditions for growth, until conditions
become wetter. In view of this spore resistance it should be remembered that, particularly in locations
where Phytophthora is present, all tools and machinery should be cleaned before transferring to another
site.
Unfortunately the chemicals known to kill Phytophthora are also toxic to the host plants. Hence, only
preventive measures can be used. This involves treating beds before planting with a soil fumigant—i.e.,
methyl bromide. Partial prevention of infestation and spread is subsequently achieved by regularly drenching planted beds with Truban or Benlate solution (3 oz. per 100 gallons) at the rate of one quart per
square foot.
At the moment careful sanitary cultural methods are the best known prevention. Heavy, wet soils with
poor drainage should be avoided. Planting beds should be raised. Irrigation should be avoided, especially
in hot weather (80°F or more), and a mulch at least one inch thick can help preserve existing moisture
and lower root temperature. If irrigation must be applied the water must not be drawn from drainage
ditches or ponds which might be contaminated.
One of the difficulties when withholding irrigation from rhododendrons during dry spells is to determine at what point soil dryness becomes critical for survival of the shrubs and hence, when watering should
Opposite:
Fig. 1 and 2. Rhododendron sutchuenense (s. Fortunei ss. Davidii),
two colour phases.
Fig. 3. R. planetum (s. Fortunei ss. Davidii).
Fig. 4. R. calophytum (s. Fortunei ss. Calophytum).
Figs. 5 and 6. Two phases of R. fargesii (s. Fortunei ss. Oreodoxa).
Overleaf:
Fig. 1. Rhododendron glaucophyllum var. luteiflorum
(s. and ss. Glaucophyllum).
Fig. 2. R. glaucophyllum var. rubiforme (s. and ss. Glaucophyllum).
Fig. 3. R. stewartianum var. aiolosalpinx (s. and ss. Thompsonii).
Fig. 4. R. dictyotum (s. Lacteum).
Fig. 5. R. russatum (s. Lapponicum).
Fig. 6. R. cuneatum (s. Lapponicum).  w^^^^ 'TH
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commence. Despite its very effective use in soil moisture retention, a surface mulch can conceal from
direct observation the moisture condition of the soil beneath it.
There are mechanical methods of monitoring soil moisture and one of these is the "soil moisture block"
method which is used in the UBC Botanical Garden. The block consists of an electrode embedded in a cube
of gypsum about 1 Vi inches square. This moisture sensor can be buried at varying depths up to three feet.
With rhododendrons care should be taken to locate some blocks quite near (within 6") of the soil surface
along with others at greater depth.
Insulated twin-core leads from the block are left protruding at the soil surface and can be connected to
a light-weight portable moisture meter. The latter measures resistance in ohms and this figure is converted
to "percentage available soil moisture" on a scale indicated by a needle. The critical point at which irrigation must commence varies according to type of soil from 25% (clays) to 65% (sands). Watering is
continued until the reading returns to at least 95%. The table below indicates critical moisture percentage
levels. It also indicates depths at which to locate soil blocks in different types of soil management.
Depth to Bur>
Soil Blocks
Procedure to Operate Moisture Meter
1—Connect lead wires to binding posts.
2—Press "To Cal." button.
3—Rotate "Cal." knob until needle rests on
right end of scale.
4—Press both buttons to read.
Tab
Color
Red
Blue
Green
White
Block
Depth
Shallow
Medium
Deep
Very
Deep
Golf
Courses
2"
6"
Not Required
For the Following Soils-Irrigate
When Bouyoucos Meter Reads:	
Sands   65%
Lawns
3"
8"
"
"
Athletic
Fields
5"
10"
■•
»
Sandy Loams      50%
Shallow
Crops
4"
10"
"
■'
Fine Sandy Loams              46%
Very Fine Sandy Loams 43%
Loam   36%
Silty Loam  34%
Clay Loam 30%
Sandy & Silty Clays 25%
Medium
Crops
6"
12"
"
"
Deep
Crops
6"
12"
18"
Not
Req'd
Very Deep
Crops
8"
14"
24"
"
Continue Irrigation Until Meter Reads 95%
to 100% Available Moisture at Desired Block
Depth
Trees
Citrus
8"
16"
24"
36"
Propagating media should be very well drained, using coarse sand, perlite or styrofoam. Bark fibre has
been found to be a very successful constituent and Dr. Harry Hoitink, of Ohio Agricultural Research and
Development Center, recommends a bark/peat mixture containing 75% bark with Vs" particle size. This
gives a maximum air space of 20% which is detrimental to the fungus. Sphagnum peat may be incorporated
but the use of sawdust in the mixture is not recommended.
Continued on page 26
Overleaf:
Fig. 1. Rhododendrons used in landscaping the south side of Crescent Road,
near Chancellor Boulevard.
Fig. 2. R. arboreum ssp. cinnamomeum (s. and ss. Arboreum).
Fig. 3. R. strigillosum (s. Barbatum ss. Maculiferum).
Fig. 4. R. 'Caractacus' (catawbiense hybrid), probably the tallest
rhododendron on the campus.
Opposite:
Fig. 1. Rhododendron degronianum 'Dalriada' (s. Ponticum ss. Caucasicum).
Fig. 2. R. vellereum (pale pink form) (s. and ss. Taliense).
Fig. 3. R. bainbridgeanum (s. Barbatum ss. Crinigerum).
Fig. 4. R. beanianum var. compactum (s. Neriiflorum ss. Haematodes).
Fig. 5. R. calendulaceum (s. Azalea ss. Luteum) in a group planting on the
north side of Crescent Road, U.B.C. campus.
Fig. 6. R. 'Elizabeth' (R. forrestii var. repens X R. griersonii) on north
side of Buchanan Building, U.B.C. campus.  What Does That Label Mean?
ROY L. TAYLOR
One of the frequently asked questions by the visitor to the Garden is "What does that label mean?" This
is particularly true of people who see the rhododendron species collection and the permanent labels which
are associated with this collection.
When the new Department was initiated in 1968 the problem of maintenance of accession records was
of major concern. To achieve an orderly development of our records an accession system was developed and
a companion computer program was established entitled BGAS*. At the same time an accession numbering program was initiated for all material in the Botanical Garden. Each accession number consists of three
parts. First, a five-digit unique number that has been assigned to an individual or collection of plants that
were obtained for the Garden. This is followed by a three-digit number which indicates the source of the
material, that is, the commercial source, individual or other source from which the material was obtained.
Thirdly, a two-digit number is assigned indicating the year in which the accessioned material was incorporated into the plant collection.
The current program calls for a metal photo-engraved label to be initiated once each new seedling or
scion or plant has been established. This small label accompanies each individual rhododendron through-
_ _ out its propagation and transplant program, and eventually it is punched and tied to the woody plant as its
*&<& permanent accession label. When the plant or group of plants from each initiation is incorporated into the
main rhododendron collection, the individual or group planting then is given a new permanent display
label made by an engraving process on a plastic laminate. This engraved plastic label is supported by a
plexiglass stake and carries both the genus, species and infraspecific taxon information, as well as the series
and subseries to which the plant belongs, and finally, the accession number from The University of British
Columbia Botanical Garden. In some cases, if it has been propagated from a special award-winning form
or special collection number such as a Kingdon-Ward 1937 Expedition Number, e.g. K. W. 13165, this information will also be incorporated on the label. It is our hope that the labelling system should enable a
user of the collection to quickly reference any material to the Rhododendron Handbook.
One source number that is of particular interest to the user of the collection is 051. This source number
indicates that the material has been propagated by the U.B.C. Botanical Garden from an existing accessioned collection. This is, of course, an important process for the Garden as it is the one way in which we
can select and develop species which are particularly suitable and adapted to the climatic regimes of this
area. In addition to the development of new material propagated from the collections, it is envisaged that
research programs will be developed to provide for additional methods of obtaining plants through hybridization and selection. In the first few years special emphasis will be directed to the increasing of our
understanding of the techniques most suitable for propagation and for the successful development of all
kinds of rhododendron materials.
Much information is contained in the BGAS system and the accession number on the label gives the
user the key to obtain much more information already stored in the system about that particular plant. The
Garden normally produces a complete printout of its holdings twice a year. However, specialized listings,
such as a compilation of all the rhododendron material and the inventory of the genus in each component
of the Garden, can be obtained at any time. The flexibility of BGAS enables easy input of new accessioned
material and editing of existing files, thus listings are up to date and new labels can be made from the
current output.
*UBC Botanical Garden Accession System (BGAS) by Roy L. Taylor, Stephen Sziklai and Annie Y. M. Cheng.
January 1973. Technical Bulletin No. 2. Published by The Botanical Garden, The University of British Columbia,
Vancouver, British Columbia, Canada V6T 1W5. Permanent photo-engraved metal accession label attached
to plexiglass stake. The label accompanies the plant
throughout its life, here seen in the propagating bed.
23
The permanent photofoil label has now been perforated
and is attached to the woody plant. Each plant in
the collection has such a label. The display label is seen in
front of the plant.
The permanent display label made by engraving a
laminated plastic material is bonded to a plexiglass stake.
Information contained on the label includes genus,
species, infraspecific name(s), other special information,
i.e. this plant from a Forrest collection no. 27089,
the series and subseries, and the UBC Botanical Garden
accession number. Societies Directly Concerned
with the Genus Rhododendron
The genus Rhododendron is a widely used ornamental throughout the Northern Hemisphere and a number of specialized societies have been developed that relate directly to this genus. In Canada, at the present
time, there are two specifically organized societies concerned with the propagation, dissemination, evaluation and promotion of the use of rhododendrons as interesting plants in the garden.
The Lower Mainland of British Columbia has long been a principal growing area for rhododendrons in
Canada and a chapter of the American Rhododendron Society was organized by growers of rhododendrons
in this region nearly 25 years ago. The chapter is a very active one and in 1970 hosted the American Rhodo-
endron Society annual convention in Vancouver. The Vancouver Chapter holds monthly meetings, frequent
plant sales and publishes a newsletter. A special study group was established in 1972 to undertake and
evaluate the study of rhododendron species. Meetings have been held at the University, and field study of
the rhododendron species collection in The University of British Columbia Botanical Garden Nursery
has been part of this program. The current address of the corresponding secretary of the Vancouver Chapter
of the American Rhododendron Society is listed below. Readers interested in this Vancouver group should
contact Mrs. Rhodes.
More recently, rhododendron growers in eastern Canada formed The Rhododendron Society of Canada. This society was founded in 1971 and was helped in its infancy by the Royal Botanical Gardens in
Hamilton. The society holds an annual show and produces a bulletin three times a year. One of the principal reasons for the development of the society was to search out and publicize information regarding hardiness in Rhododendrons (see editorial in the first issue of the Bulletin). Although initially there was some
QzA feeling of estrangement by the Pacific Coast rhododendron growers with the development of The Rhodo
dendron Society of Canada, there has been a good acceptance of the society by Pacific Coast growers
indicating that many of the problems are similar across Canada. The secretary-treasurer of The Rhododendron Society of Canada is found below.
The Rhododendron Species Foundation, with which The University of British Columbia has been
closely associated for nearly 10 years, was a private interest group of rhododendron growers belonging
to the American Rhododendron Society who had a special interest in developing and preserving a collection of rhododendron species of known value from gardens in Europe. Dr. Milton V. Walker, one of the
prime movers, actively pursued the development of the Foundation and his enthusiastic initiative has led
to the establishment of a Rhododendron Species Foundation collection at Salem, Oregon under the direction of Mr. P. H. Brydon, former Director of the Strybing Arboretum at San Francisco. The close relationship between the U.B.C. Botanical Garden and the Rhododendron Species Foundation has been elaborated
on in the article entitled "Rhododendron Species—A Developing Collection at U.B.C," starting on page 14.
Persons desiring more information about the Rhododendron Species Foundation should contact the secretary at the address given below.
CONTACTS FOR SOCIETIES
Mr. P. H. Brydon, Secretary Mrs. Jean Rhodes
The Rhododendron Species Foundation Corresponding Secretary
Rt. 1, Box 748 Vancouver Chapter American Rhododendron Society
Salem, Oregon    97304 21471 Cherry Avenue
Maple Ridge, B.C.
Dr. H. G. Hedges
Secretary-Treasurer
Rhododendron Society of Canada
4271 Lakeshore Road
Burlington, Ontario
Opposite: Rhododendron houlstonii in a mature planting in the Place Vanier
residence complex. This species belongs to the series and subseries
Fortunei and is a native of S.W. China in Hupeh and Szechwan. ft ~
5^ ^^*^« From page 20
If the following propagation procedure of Dr. Hoitink is followed Phytophthora should be avoided:
1. Propagate in sphagnum peat and perlite.
2. Transplant into sphagnum peat and sand; use coarse concrete sand from a gravel pit or river bottom.
3. Transplant in a bark mix, preferably more than 75% bark.
4. Use baskets or well-drained containers placed on gravel, not on plastic.
A search is going on for resistance to Phytophthora in rhododendrons in the hope of introducing resistance
2(3 on a broad scale. Of scores of species and hybrids tested only a few hybrids such as 'English Roseum',
'Koster', 'Dr. Arnold Endtz' and 'Vulcan' show good, but not complete, resistance. Their roots are still
attacked by the fungus but killing is slow and new roots are able to replace infected ones at a faster rate.
The disease is not confined to rhododendrons and azaleas. Other ornamentals, such as Pieris, Chamaecy-
paris, Taxus and Pinus can be affected and should be watched for wilt symptoms.
Until and unless good resistant strains can be produced growers must adhere to strict cultural methods,
avoid areas with high summer temperatures and especially avoid irrigation at such periods. Only by stringent sanitary measures can the disease be avoided or controlled.
CLIMATOLOGICAL SUMMARY1
Data                                                              1973
April
May
June
Mean temperature
47.65°F
54.15°F
56.65°F
Highest temperature
59°F
82°F
77°F
Lowest temperature
35°F
38°F
44" F
Grass minimum temperature
23°F
26°F
34°F
Total rainfall/No. days with rainfall
0.60"/7
2.05"/9
2.48"/13
Total snowfall/No. days with snowfall
nil
nil
nil
Total hours bright sunshine/possible
213.6/404.02
261.8/468.03
213.7/482.29
Max. wind speed (m.p.h.) for 1 hour/
direction
ll/NW&SE
13/E&SE
15/E
Mean mileage of wind at 3'
67.2
87.9
77.3
Mean mileage of wind at 40'
97.4
126.6
111.2
*Site: The University of British Columbia, Vancouver, B.C. Canada
Position: lat. 49°15'29"N; long. 123°14'58"W. Elevation: 342.6' Opposite
A few of the fine specimen rhododendrons
from the Triangle Garden area near the
Rose Garden. Left: Rhododendron 'Robin
Hood' (calophytum X sutchuenense).
Right: R. sutchuenense (s. Fortunei,
ss. Davidii) in the foreground.
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 Assistants
Mrs. Marilyn G. Hirsekorn
Mrs. Sylvia Taylor
Secretary to the Office
Mrs. Susan Weiner
Senior Technician (Horticulture)
Mr. A. James MacPhail
Plant Accession System
Mrs. Annie Y. M. Cheng
Senior Gardener
Mr- James O'Friel
Gardeners
Mr. Harold Duffill
Mr. Leonard Gibbs
Mr. Sam Oyama
Mr. Pierre Rykuiter
Mr. Tomomichi Sumi
Mr. David Tarrant
Mr. Isao Watanabe
Mr. William S. White
Flora British Columbia Program
Dr. Roy L. Taylor (Editor)
Dr. Bruce MacBryde (Associate Editor)
Miss Deborah Smyth (Secretary)
Mrs. Sylvia Taylor (Research Assistant)
Plants and Man', the logo of the
UBC Botanical Garden emphasizing the
understanding of the interaction of plants
and man through the achievement of the
objectives of the Botanical Garden program. Volume 4
DAVIDSONIA
Number 2        Summer 1973
Contents
Introduction to the Rhododendrons on Campus    11
Rhododendron Species—A Developing Collection at UBC    14
Rhododendron Species    16, 18, 19, 21
Phytophthora Root Rot of Rhododendrons    17
What Does That Label Mean?    22
Societies Directly Concerned with the Genus Rhododendron    24
Climatological Summary    26
*Pf'IC«   prr(-*T1**C LTD.

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