JARS v54n3 - The Yellow Rhododendron occidentale

The Yellow Rhododendron occidentale
Britt Smith
Kent, Washington

Early in the search of Rhododendron occidentale in its native habitat, Frank Mossman and I became acquainted with Jimmy Smith. Jimmy and his wife had a small nursery beside Highway Route 101 in the southern part of Brookings, Oregon. There were plants of R. occidentale growing all around the area and Jimmy was quite interested in them. One of his acquaintances was a logger who told him of an occidentale growing at the edge of the forested area, bearing flowers which were completely yellow. But, Jimmy reported, the logger would neither bring Jimmy a truss nor tell him where that plant was growing.

Not long after that Jimmy sold his home and nursery, and we lost track of him. But Jimmy had "planted a seed." Subsequently an effort was started to make a "yellow occidentale ". This seemed well within the potential of intraspecific crossing because occidentale "in the wild" exhibits such a wide range of variability. Plants were found with color variation from almost white to almost yellow as in SM 12 to deep red as in SM 205 (see box on next page for explanation of numbering system). Some had extra lobes as in SM 136 and SM 165, and some were double with stamens converted to petals, as SM 28 and others. Some had attractive picotee edges, as SM 502 and SM 307, and some had strongly frilled edges on the lobes, as on 'Stage Coach Frills' and SM 232. Some have flowers to 4 inches (10 cm) in diameter. On some the flowers are divided to the ovary. SM 601 has fifty or more flowers per truss.

The quest of the yellow occidentale was irresistible, and SM 30 seemed a "natural" because it has yellow on every lobe. It was crossed with SM 247 because that plant produces flowers which seemed to show traces of yellow all over each flower. That cross produced plants designated 83-39, 84-142, and 85-20, which were chosen to be parents for the next generation (SM 30 x SM 247) _F2 and that group included a number of very interesting progeny including 91-102, 91-105, and 93-101, plus others. Eureka! It seems that the goal is attainable!

At about the same time, it was decided to test the sustainability of flower size through an intraspecific crossing. Primary parents in this experiment were SM 232 and SM 148, each of which had large flowers, particularly SM 148, with flowers to 4 inches (10 cm) in diameter. This F ₁ cross produced 83-35 and 83-36, each bearing flowers as large as or larger than SM 148.

SM 28, SM 28-1, SM 28-2, and SM 28-3 were found growing in a floriferous area no more than 50 feet (15 meters) in diameter, in "LeMunion's Pasture" in Crescent City, California. Each consistently bore flowers with ten or more lobes. Crossing SM 28-2 and SM 28-3 produced progeny with ten or more lobes on each flower. This, however, was not consistent among those offspring. The experiment was not carried beyond the first generation. It seems appropriate to mention here that Dennis Hughes, of the Blue Mountain Nursery in New Zealand, has developed azalea plants producing flowers up to fifty-two lobes each, but we do not know the parentage of those.

The same sort of experiment was conducted relative to picotee edges, and that characteristic "carried through" to the progeny in the first generation, but second generation "carry through" of this characteristic has not been attempted. In the case of SM 30 x SM 247, it took only two generations to achieve desired results. The potential for exploration and understanding in this field seems untapped!

The South King County Arboretum Foundation is establishing a garden with as complete a collection as possible of the Smith-Mossman Rhododendron occidentale clones. This garden is located at 22500 S.E. 248th St., Maple Valley, WA. A dedication of the garden was held June 9, 2000.

It is intended that the information here suggest and encourage experimentation. Britt Smith joins with Steve Hootman, Curator of the Rhododendron Species Foundation, and Bob Dunning, president of the South King County Arboretum Foundation, to advise and assist anyone who is interested in undertaking a serious study of intraspecific crossing in this species, particularly for reporting the findings in a thesis for an advanced degree.

Explanation Of The Smith/Mossman Numbering System
In designations SM 1, SM 2, etc., these were assigned to species plants as they were found during the first year of exploration. During the second year, numbers SM 101, SM 102, etc., were assigned in the order in which they were found. In the third year, numbers SM 201, SM 202, SM 203, and on, were assigned. In the sixth year, numbers SM 501, SM 502, SM 503 and on, were assigned.

The system for designating any selected hybrids in my garden was, for example, 83-70. This plant was first noted, designated, and photographed in 1983 and was the 70th in sequence blooming in my garden that year.

Britt Smith has co-authored two articles with Frank Mossman for the Journal on Rhododendron occidentale. They include "Further Trips to the Rhododendron occidentale Patches" (Summer 1968 issue), and "Rhododendron occidentale - One Species or Many?" (Summer 1969 issue).