Further Trips to the Rhododendron Occidentale Patches
Frank D. Mossman, M.D., Vancouver, Wash.
Britt Smith, Kent, Wash.
Paper presented at the A.R.S. Annual Meeting, Eugene. Oregon, May 12, 1968
Accompanied by numerous slides
This is the first of a series of programs to be presented under the general heading "Modern Day Rhododendron Expeditions." When we think of expeditions we think of trips to Japan as taken by Frank Doleshy or to New Guinea as by Maurice Sumner, or Taiwan as by Dr. Creech and about which you will be told in subsequent programs during the next two days. To those men belongs a great deal of credit and the pleasure which they add to our growing of rhododendrons should not be forgotten. Also we must remember the early rhododendron expeditions of Forrest, King-Ward, Rock, Ludlow and Sherriff, Cox, Mr. Yu, and many others. These men provided the basic stock for the beautiful rhododendrons which grace our gardens today. We envy each of them for his expedition and experiences.
It hardly seems right to call a trip of 500 miles each way an expedition, but we have found great pleasure in taking those trips which include visits to places with exotic names like Denmark and Trinidad. It is our good fortune, and yours if you choose to make it so, that R. occidentale grows close enough to home that we and you are able to visit a sizeable area several times a year. We hope that you will derive as much pleasure from hearing of our trips and seeing the pictures as we derive from telling you about them and showing you the pictures.
R. occidentale was first discovered by the expedition of Captain Beechy in 1827, and was later collected by Douglas, Hartweg, and Burke. William Lobb receives the credit for introducing this azalea into cultivation about 1850 when he sent seeds to the Veitch Nurseries in England where flowers were seen about 1857. Anthony Waterer, Sr. flowered R. occidentale at Knap Hill about 1860, and later made the first. hybrids with other azaleas. Ninety years later Mr. Leonard Frisbie of Tacoma, Washington made the first extensive survey of R. occidentale. Mr. Frisbie's intensive work covered a span of about ten years during the 1950'x. In this truly monumental work he examined distribution, ecology, and synecological associates. He made many field trips by bus, train, jeep, and foot, collecting significant forms. The clone Tacoma #158 'Rogue River Belle' has been sent by him to plant lovers over the world. Mr. Frisbie sought and received the help of many interested scientists at universities in Oregon and California. He published a summary of his investigations in January 1961.
Our trips have taken us to southwestern Oregon and northern California, as far north as Riddle and Bandon in Oregon and as far south as Redding and Eureka in California. Both coastal and inland areas explored have produced interesting clones. Hunting may be easy or difficult. Pasture situations may be strolled with ease, whereas bramble tangles in gullies or on hillsides may require special protective clothing and the stamina of a mountaineer. Hedge rows can often be viewed from the auto. Morning always brings heavy dew so water repellant clothing is needed at least part of the time. Rain is frequent. Cameras suffer.
Sometimes bushes grow separately as specimens. In logged areas plants are damaged but the remaining roots send forth vigorous new canes. More often tangled masses of many plants make identification of root systems difficult; the effort to do so requires searching with an ungloved hand which too frequently contacts unnoticed berry vines entwined there. Rhododendron occidentale seeks water, growing along streams, in gullies, on spring-dampened hillsides, or on marshy plateaus.
We have found patience a necessity, successful hunting requires that we inspect every bush, and almost every flower thereon. Our judgment seems adequate only when we are close enough to hold the flowers in our hands. We find that judgment dulled by the visual stimuli and the wonderful fragrance of the R. occidentale patch. After viewing several hundreds of bushes over a period of many hours we experience mental and physical fatigue. The SM 28 series of double flowering hushes was almost missed because of such weariness.
The fascinating characteristic of R. occidentale is the variety of forms. In two years about 170 clones have been collected for further study, and these from many thousands of plants inspected. One hundred seventy may seem too many-or maybe too few. The pictures will illustrate the problem of selection. You will see some duplication or near duplicates among them.
A decision to catalogue a particular bush is made by a brief discussion between the two of us. Is this one bigger? Smaller? Different in color or form of flower? A positive decision means work. First a description of the shrub and flower, location, marking, pictures, and collecting propagating material. We feel that a reflex camera is essential for close pictures-within inches. We use color film with an ASA rating of 160 in order to get the smallest possible aperture and thereby achieve the greatest depth of focus. We have found that flowers should be viewed and photographed in the shade. Full sun interferes with the best color evaluation by eye or by film.
Propagation by vegetative techniques is the immediate concern with a selected clone. Half-ripe green wood cuttings taken in May-June-July at or soon after the time of flowering have been successfully rooted. Layers or small plants taken in the spring or early summer do better with nearly all top wood removed. We replant these in half shade and water copiously. Layers or plants which are root and top pruned in June have been successfully transplanted in August with short new top growth. August is the dry season; a time of relative dormancy and, for us, a satisfactory time for transplanting R. occidentale. All wood may be retained on small plants. Air and ground layers form readily.
When R. occidentale grows in soil which provides ample moisture the root system is compact as is found with cultivated rhododendrons. When R. occidentale grows in a dry situation, one or more tap roots are found extending from the bottom of the compact root system which is near the soil surface. We have not attempted to determine the depth to which these tap roots grow, but it is far beyond the usual maximum depth for domestic rhododendrons. These tap roots have been severed when the plants were dug and the plants do not seem to suffer when they receive plenty of water in their new situation. We have raised some plants from leafless cuttings taken in November-December. A later report is planned for this subject.
Propagation from seed is gratifying. Hand-pollinated seed is allowed to develop for 100 days or more. Pods are not allowed to tan or split lest we lose seed. Plants to 18 inches tall have been raised in one growing season by starting them in a mixture of equal parts of Canadian peat and heat-sterilized peat soil. They are germinated and kept under lights until transplanted the first time and then are moved to a cool house. Liquid fish fertilizer is the only supplement.
Hardiness of R. occidentale is stressed because of some misgivings about its ability to survive outside its native environment. Mr. Frisbie found this azalea in the Donner Pass area at altitudes of over 6000 feet, obviously cold hardy. Mrs. J. Norman Henry grew and admired two color forms of R. occidentale at Gladwyn, Pennsylvania, for many years. Knap Hill Nursery in Surrey, England, has large plants of R. occidentale over 100 years old which have survived 40 degrees of frost in some winters. Some eastern U.S. gardeners report that the species survives the rigors of winters but seems to be adversely affected by eastern summers. Mr. William Lobb made his collections as far south as the San Diego area and it is possible that some of those were tender forms. Generally R. occidentale seems extremely hardy, and it is possible that they will thrive in eastern summers if they are supplied enough water.
Generally the flowers of R. occidentale are consistent from year to year. Observations made during only two seasons indicate that consistency can be expected but is not certain. 'SM 12' in 1966 bore extensive development of petaloid stamens on approximately half its flowers. In 1967 the petaloid feature was present only as little tabs at the centers of the corollas. It was also observed in 1967 that the normal petals were not nearly as wide as in 1966. Perhaps the same casual factors were involved in both these changes. The color of 'SM 12' was the same during both seasons.
It was the impression of the authors that the 1967 blooming season somehow brought florets containing much more blue in their coloring than in the previous season. This was not true of all flowers, and the degree varied.
Some double flowering plants produced more beautiful double flowers during 1967 than during 1966; examples are 'SM 28' and 'SM 28½.' On the other hand 'SM 34' which had beautiful petaloid stamens, evenly spaced and five per floret in 1966 did not do nearly so well in 1967. Most flower colors, sizes, and shapes remained stable for the two seasons. We have confidence that the proper balance of water, sunshine, fertilizer, and humus in the soil will produce more beautiful flowers each succeeding year if plants are moved from their native environment into cultivation.
R. occidentale types tend to grow in groups. All of our persistently double-flowering clones were found within an area of 300 yards diameter.
R. occidentale was a very important element in the development of the Knap Hill azaleas and later the Exbury strain. The "square-faced," wide petaled flower sought by the Waterers and de Rothchilds was produced in nature long ago in some forms of R. occidentale. 'SM 35' and 'SM 183' are but two examples.
Indications are that the Knap Hill and Exbury azaleas were developed using comparatively inferior forms of R. occidentale. Now we are looking forward with great anticipation to the possibilities from hybridizing and intra-specific crossings of these beautiful forms which we have found and will find. It seems that the possibilities are tremendous!
|Interesting Smith-Mossman R. occidentale selections:|
|All numbers over 100 were selected during the 1967 flowering season.|
|a. Our deepest yellow-flowered bush so far 'SM 12'. Virtually the same yellow color overall.*|
|b. Very deep pink-flowered forms: 'SM 29', '126', '163'.|
|c. Plants on which every floret has petaloid stamens. Fifteen bushes in all. The largest flowered of these being 'SM 28-2'.*|
|d. Plants on which every floret has more than the normal five petals without significant petaloid changes in the stamens. 'SM 22', '36', '136'.|
|e. A plant with orange-yellow color on every petal 'SM 30'.*|
|f. A plant with flowers up to four inches in diameter, 'SM 148'. Our largest so far. The petals are frilled, creped, and broad.*|
|g. A plant with flowers only ⅜ inch in diameter. 'SM 157', 'Miniskirt'. Similar to a form reported by Frisbie, but later lost in a forest fire. Other intermediate small flowered forms have been found in several places.|
|h. Highly frilled flowers, 'SM 125', '127', '154' and others.|
|i. Wine-colored flowers, 'SM 147', '151', '160'.*|
|j. Flowers on which the standard is entirely covered with deep orange-yellow color, 'SM 112', '153'.|
|k. Plants on which almost no yellow color is present in the standard, 'SM 5', '21', '151'.|
|1. Flowers with no pink at any time in bud or flower, 'SM 186'.|
|m. Flowers with maroon to orange-maroon-colored flare on the standard, 'SM 176'.|
|n. Flowers with nearly all petals red-margins, 'SM 113', '120'.*|
|o. Flowers with all petals quite broad to overlapping, 'SM 35', '125', '183'.|
|p. Highly creped petals, 'SM 7', '30', '55', '148', and others. Longitudinal folds running the length of the petals giving them a twist so that no two flowers are shaped the same.|
|q. Distorted flower forms in which the petals and even the style are divided to the ovary, 'SM 53' and 'freak'.*|
|* Indicates that we have been unable to find a record of other R. occidentals flowers of this description.|
Frisbie, Leonard, 1961, Rhododendron occidentals survey, Rhododendron, Jan.
Frisbie, Leonard and Dr. Edward Breakey, 1955, Rhododendron occidentals, R. H. S. Rhododendron and Camellia Yearbook.
Henry, Mrs. Norman, 1946, Deciduous Rhododendrons at Gladwyne, R. H. S. Rhododendron Yearbook,
Street, Frederick. Azaleas.
Waterer, G. Donald,1950, Rhododendrons and Azaleas at Knap Hill Nursery, A. R. S. Quarterly Bulletin, vol. 4 No. 1.
Wilson, E. H. and Alfred Rehder, A Monograph of Azaleas.