JARS 43n1 - Deep Red Rhododendron maximum At Barnard's Inn Farm

Deep Red Rhododendron maximum At Barnard's Inn Farm
Polly Hill
Vineyard Haven, Massachusetts

In June 1960 a group of keen plantsmen hiked ten miles up Mt. Mitchell in North Carolina to secure a very special plant. The seven men were: Dr. Henry Skinner, Dr. Nick Fortescue, his son Nick Jr., J.R. Brooks, Henry P. Yates, Clem Bowers, Joe Gable. With much hard labor they brought back a plant to the U.S. National Arboretum, where it was given the number, NA 15524-C, Rhododendron maximum . At 4,000 feet on Mt. Mitchell it had deep red blossoms. But in D.C., in the Arboretum, it flowered pink and white year after year, never red. Just in case there had been an error at the Arboretum a second expedition was mounted with all the same results. The question arose, why?
In July 1972 Dr. Skinner brought me a rooted cutting of NA 15524-C to see if the cooler climate of Martha's Vineyard would induce red flowering. In 1975 it was planted out from my nursery to the west field where it bears the BIF number 72-108 in addition to the NA number. In June of 1987 my plant produced a few branches with deep, almost blood red flowers, in addition to its pink and white flowers. These photographs were taken at that time.

R. maximum 72-108-A
R. maximum 72-108-A
Photo by Polly Hill

In 1980 I had the good fortune to receive a plant from the Massachusetts Chapter of the American Rhododendron Society called R. CV. Red Max. It bears my number BIF 80-053. That plant was a grafted scion from the Lee Memorial Garden in New Canaan, Connecticut, grafted on 'Cunningham's White' in the fall of 1979. In June 1987 it also bloomed, but only pink and white, although perhaps a richer pink than the average R. maximum .

R. maximum 80-053 (syn. Red Max) R. maximum 72-108-A
R. maximum 80-053 (syn. Red Max)
Photo by Polly Hill
R. maximum 72-108-A
Photo by Polly Hill

Dr. David Leach tells me that in 1956 or '57, he went with a group of men including Warren Baldsiefen, Joe Gable, Milo Coplan and Ernest Yelton looking for the red flowered R. maximum colony thought to be on Mt. Mitchell. They each brought back a little plant or two of self seedlings that varied considerably in the intensity of red in the flower. Dr. Leach took self seeds from Warren Baldsiefen's plant and named the best seedling 'Mt. Mitchell'. It is registered and described in the ARS Bulletin (Vol. 18:1, January 1964). He has two plants now, five to six feet tall, which he describes as superior to R. maximum in their foliage density. The sap is red and there is a layer of red tissue beneath the surface green of the stems. A red pool is visible in the center of an immature leaf when it is held up to the light. This sounds to me more like my grafted Red Max than my red flowered form.
I suggest that these photographs will show that my two plants are separate cultivars and not propagations of the same individual.
Searching for horticultural answers always seems to involve a welter of variables; weather present, weather past, how far past?, soils, nutrition, injuries. What was involved here? It is appropriate to state that there was a late freeze on May 14th 1987 in the low twenty degrees Fahrenheit. If that low temperature triggered something on one plant, why not also on the other? If, in addition to temperature, altitude is involved, Barnard's Inn Farm is only about fifty-nine feet above sea level, quite a drop from 4,000 feet on Mt. Mitchell.
Geneticists have suggested that a chimera* might be involved in this event. I even read 159 pages (33 of them were references) on "Plant Chimeras" by R.A.E. Tilney-Bassett. It was clear that he enjoyed them and carefully described their genetic diversity and took delight in their color variations. But nowhere did I notice the words altitude or temperature used as an explanation for their origin. Colchicine treatment was not involved in my case. Mutation is a mystery which seems to me very close to the idea of chimeras.
However that may be, how is one to explain this particular occurrence on my red flowered R. maximum ! I find that the answers I seek are as elusive as the search for them is seductive.

*Chimera -" ... a plant containing tissues from at least two genetically distinct parents." (American Heritage ' Dictionary , 1982)

Polly Hill is a keen observer of rhododendron species and their variations.
For more information on David Leach's red R. maximum see ARS Quarterly Bulletin (Vol. 19:2).