QBARS - v11n3 Rhododendron Notes

Rhododendron Notes

This has been a good growing season in the Northwest, and an early one. We wonder if the "early" seasons aren't usually the best for rhododendrons.
Comment from an out-of-towner at the Portland Show "This Rhododendron Island is one of the few things I have gone a long way to see which has fully come up to my expectations."
Rhododendron Parks are also being developed by the Eugene and the Tacoma Chapters. Do other Chapters have plans for projects of this kind?
The Orchid growers also have problems of nomenclature, probably a good deal more complicated than ours. The International Code of Nomenclature is necessary as an over all instrument but a simplified code for an individual plant group, such as the A.R.S. Code, can be very helpful. It will be interesting to see how the Orchid people solve their problems.
"Rhododendrons 1956" is no longer the only existing publication to differentiate horticultural varieties as "clones" and "groups." The new R. H. S. Handbook has marked with "cl" or "g" all names in the Stud Book, but some are marked with both symbols, as for instance 'Aladdin,' so a gardener buying that variety might still get the clone he wants, or just a seedling of the cross.
Before printing "Rhododendrons 1956" we asked competent English authority if any of the varieties in the Stud Book had actually been introduced as single clones and the list came back indicating that all should be considered as groups, presumably because someone in the future might make the same cross and use the group name for his seedlings. Now it would seem that the R. H. S. might go one step further and indicate that anyone making the cross R. didymum X R. griersonianum , for instance, should not call the seedlings 'Arthur Osborn' as that name is listed in the Stud Book as a clone. Let's keep working at this problem until the ambiguous names have been so defined that their meaning is completely clear.
The use of sawdust as a mulch or soil conditioner for Rhododendrons continues to arouse some discussion on the part of garden writers, some still "viewing with alarm." It is our feeling that if water and nitrogen levels are properly maintained sawdust is a very valuable material. In fact one nurseryman recently told me that if it weren't for sawdust he would be out of the Rhododendron business. Probably the most serious fault of sawdust as a mulch is that, under certain conditions, there may be more likelihood of frost damage because bare earth would radiate more heat. But that applies more or less to all mulches, although, so far as I know, the scientists have not yet measured the effect of various kinds of mulching materials on heat radiation from the soil on frosty nights.
Prof. A. N. Roberts of Oregon State College some time ago gave a very interesting paper before the Portland Chapter in which he brought out the fact that much better results were secured with Azaleas (and presumably with other Rhododendrons) if the nitrogen fertilization was with the ammonium rather than the nitrate form.
Those who are interested in the technical phases of this very important work should look up the following reference. Colgrove, M. S. and A. N. Roberts. Growth of the Azalea as influenced by ammonium and nitrate nitrogen. Proceedings American Society for Horticultural Science, Vol. 68, 1956, pp. 522536.
- J. Harold Clarke

Mrs. Ruth Martin Hansen, secretary-treasurer of the American Rhododendron Society, was recently given the Garden Club of America Horticultural Committee award for horticultural achievement within the club. This was for her work with rhododendrons. Besides her work as an officer of the rhododendron society, Mrs. Hansen who is a landscape architect planned the planting for the Rhododendron Test Garden. It was her active interest which helped make possible the combination cool house and exhibition house at the garden.
Two more fine seedlings from the Dr. Rock 1949 collection bloomed this season. R. bainbridgeanum (Rock No. 48), is creamy-yellow with a crimson blotch in the throat. R. himertum (Rock No. 128), has a loose truss of seven light lemon-yellow cup-shaped flowers. This compact growing plant is rated "A" in hardiness in the RHS Handbook.
The best planting of dwarf rhododendrons we saw this season is at the home of Mrs. Philip Hart on S. W. Edgecliff Road, Portland. This group of plants on a hill side facing the Willamette River are quite exposed to weather and sun. They thrive in this location. Six large and very old plants of R. sargentianum are outstanding, each nearly two feet across. A big plant of R. lepidostylum with its grey-green foliage is beautiful, as is a unusually deep yellow R. flavidum . Other big plants are R. camtschaticum , fastigiatum , haematodes , hippophaeoides , impeditum , intricatum , keleticum , leucaspis , pemakoense and trichostomum .
The rare and beautiful Gaultheria forrestii grows well here as does a rock-clinging European form of Loiseleuria procumbens . Background plants are R. wardii , campylocarpum , smirnowii , brachyanthum ; a number of hybrids and a wonderful deep pink form of R. schlippenbachii .
A recent California visitor writes, "We are still in a daze over the beautiful plants, dogwoods and gardens we saw in Portland. The rhododendron park was wonderful."
An English visitor said the Society Test Garden in Portland is one of the finest planting of rhododendrons he has seen. Out-of-state visitors speak highly of it and wonder why it is not better known. Even Portland people are not too familiar with it. A group of 60 women garden club members recently toured the park. Only two of them had heard of it. Seven years ago the site of this Rhododendron Test Garden was just a three acre island in Crystal Lake Springs. Part of the parks department of the City of Portland it was undeveloped, overgrown with big trees and covered with brush and poison oak. Today the Test Garden contains over 2500 rhododendrons, many 6 to- 12 foot in height, planted in open woods and viewed across wide expanses of well-kept lawns. These plants, about 600 varieties of species and hybrids, grow to perfection here where they are quite protected from strong winds and the temperature is tempered by surrounding water. The new 40 foot cool and exhibition house houses a good collection of the tender varieties while the surrounding roofed patio forms a protected show space. This work has been done in less than seven years. In October, 1950, the first plants were moved to the Test Gardens, two 40 year old plants of Cynthia. This work has been so well done that two or three years ago the Parks Department asked the Society to take over an adjoining tract of land and developed it. To make this possible the Parks Department built a foot bridge from the island to this wooded tract, and a good portion of this new part of the Garden has now been planted. The city also built a parking area for the Garden. Maintenance of the island is done by the Parks Department. Planting is done by the members of the Portland Chapter of the American Rhododendron Society. Plants have largely been donated by growers in the Portland district.
In articles on propagation mention is often made of "potting the rooted cuttings." But we have never read of a reason for this. Rhododendron roots grow fast, quickly fill a pot then the plant becomes root bound. It will often be two or three years before all roots will break out of this tight root ball. Rooted cuttings lined out on the greenhouse bench or in the cold-frame in peat or your regular growing mixture can freely developed roots.
- Bob Bovee