Reliable Rhododendron Species for Pacific Northwest Woodland Gardens
Rudolph Henny, Brooks, Oregon
This paper was prepared by our Bulletin Editor shortly before he passed away,
for presentation before the Seattle Chapter, but was never given.
Mr. President, Members of the American Rhododendron Society. My talk to you tonight will in several instances be of a rather divergent nature. Though the main address will be titled "Some Reliable Rhododendron Species for Pacific Northwest Woodland Gardens," I will show some slides of a few species, several of my newer hybrids, and a number of Japanese Flowering Cherries, also a Magnolia or two.
This short paper will not attempt to touch on the many hundreds of species of rhododendrons grown here in the gardens in the Northwest, but rather it will focus on a rather small group of long time favorites that are reliable and possess no small merit as to ease of culture, and a certain elegance of beauty. Of course, rhododendron species, while not in every garden or collection, are quite numerous and popular in gardens of rather larger size. As I have mentioned this particular group will include less than 15 species, and are plants of easy culture, and I ask no one to take it amiss if some of the latest and most sought after species are not amongst them.
I think the finest group of plants are represented in the Triflorum section, and the following five are great favorites throughout the Northwest. R. augustinii, is a beautiful plant in many shades of blue. Some forms are much hardier than others, and in recent years clonal forms from here and abroad have been distributed. I would like very much to mention early that the clonal forms, wherever obtainable in the species, are the ultimate. Anyone that has ever raised a group of seedlings of R. augustinii is well aware that they range from fine blue to rosy mauve or other uninteresting shades. The clonal form 'Barto Blue' found by Dr. Phetteplace in Eugene has proved very hardy, and has large fine blooms borne in great profusion. I will not name others as the list is long, but in the clonal forms now available there are enough to fit and suit any taste. I will include R. chasmanthum since it is very near R. augustinii in habit, form and coloring, and I find it is often mistaken for the former. Large bushes of the above are effective in the woodland and even as specimens in the garden.
R. oreotrephes in its better forms is outstanding. It is quite hardy throughout, and does not have the very tender individuals amongst its offspring. I have several large plants of this species, and they are seldom injured by the coldest weather. The foliage is shiny, from green to blue shades, and many plants are marvelous since they take on an altogether different foliage color during the winter months. The corolla color is variable from seedlings and ranges from magenta to pink. From the Rock seeds sent back in 1948 I have found a white form, though I am sure that the latter is not common.
R. pseudoyanthinum is a highly variable plant as to color which could range from royal purple to burgundy red, and some shades of very muddy, dirty pink. I raised one of the latter to quite a large bush, and it is now the prize specimen in a friend's garden who, to all appearances, cherishes it very highly. The best forms are of a color like 'Purple Splendour' or burgundy colors nearing maroon red. Several years ago I introduced the clone 'Purple Fake.' R. pseudoyanthinum has recently been merged and in the future will be known as R. concinnum var. pseudoyanthinum.
R. lutescens is an early blooming yellow of open growing habit that shows its bloom in the very early spring or late winter. This early blooming habit will see the bloom caught many times in a frost, but the lightness of the habit of this plant, so characteristic of the members of the triflorum group, makes it a great favorite. The FCC form has larger bloom, but I think it is a bit less hardy than others. There is another very fine form in the Test garden in Portland, and I have made several tours in the early spring especially to see it. Many years ago Wales Wood gave me a plant of R. lutescens that I have since named 'Woods Hardy' form. The bloom is a bit smaller than other forms, but it is an intense yellow, and has never been cut down by frost.
R. davidsonianum is one of several of the finest rhododendrons that we can grow. The FCC form is a very fine pink, and the A. E. form, named 'Ruth Lyons', from the Barto Collection, is very nearly like it. These willowy large plants are simply exquisite in the spring. 'Serenade', another of the Barto plants, is also recommended.
R. schlippenbachii that is hardy even on the east coast is also a favorite in west coast gardens. The color ranges from white to a very fine pink. The forms that should be sought after are the pinks that come into bloom before any of the foliage is evident. I am not aware that any clonal forms of this are being propagated, but there surely should be. A good pink form from the Esch nursery is in the Test garden.
R. sutchuenense. Most plants grown in the gardens are the variety geraldii with a deep maroon basal blotch. Superb forms with larger blooms are now in evidence, especially the A.M. form with its large flowers. Almost as large blooms though are noted on a plant raised from seed by Cecil Smith. Light frosts in the early spring seem not to damage the bloom. Actually the plant in twenty years will make a small shapely tree.
A most remarkably prolific bloomer is R. fargesii. Most plants from seed vary somewhat in color and the degree of spotting, but I can say that I have never seen a poor form of this species. Dr. Phetteplace has registered the clonal form 'Barto Rose' which I think is highly "descriptive. An excellent form was shown also in the Eugene Test Garden. I am aware of at least four forms of this plant that should be named as fine clones. The gardener must pick off all the spent bloom for every terminal will have buds, and the profuse setting of seed will greatly injure this variety. The plant is hardy, and will bloom in late March, and will almost never fail to put on a real display.
R. rubiginosum and R. desquamatum are two delightful species. I have placed these two together since they are very much alike. Both are hardy, easy to grow and have a fine upright habit. The color ranges from white through clear pink to mallow purple. Plants from the 1950 Rock expedition have shown some very fine, clear pinks, and last season I had the opportunity to see some growing in the Test Garden in Portland. Several years ago I named a clonal form 'Finch'; it is mallow purple. During the storm in October a large fir tree toppled on it, and broke it to the ground, but I hope that it will recover in the years to come. It has made considerable growth.
The large leaved species R. fictolacteum and R. rex, are two very fine trees for the woodland garden; both are hardy enough to withstand the coldest weather we have and, given partial shade out of the wind, they are among the best plants that can be grown here. There is very little variance but pinker forms of each do exist. I am not aware of any named clonal forms of these species, but several fine forms have been called to my attention.
I cannot overlook the marvelous species R. mucronulatum. This species many times blooms in mid February when no other plant is in bloom, and the sight of a large plant in full flower at that time is an outstanding novelty. I must also again state that I have never seen a poor form of this in bloom during the dull days of late winter. A clonal form is 'Cornell Pink'.
R. calophytum is a stately small tree with fine pink or white bloom in early March. This species, along with R. fictolacteum and R. rex, is among the hardiest and most reliable of the larger leaved plants. R. calophytum never fails to impress in the garden landscape. The color ranges from pale pink to mostly white. Forms exist with buds of maroon color rather than the usual green, and it was thought that these would have pinker bloom, but it has not been an indicator as such. It has the contrasting green pistil.
R. williamsianum. This charming small bush is easy to grow, and does very well in most instances. Some forms take years to bloom, others recently introduced, are reportedly much faster. In all cases R. williamsianum is one of the finest species which will eventually grow to make a compact bush. Several forms exist, ranging from pink to white, and others have almost tubular bloom although this probably suggests hybridity.