Confusion Of Names - Confusion Of Plants
The Case of Rhododendron Maximum Roseum
John C. Wister, Swarthmore, Pa.
Sometimes it seems that botanists and horticulturists, the very people that should be studying and enjoying plants together, are worlds apart. There seems to be so little communication and so little cooperation between them that it gives the impression that never the twain shall meet.
Rhododendron 'Maximum Roseum' is one of the extreme cases which prompt the above feelings. In Rehder's "Manual of Cultivated Trees and Shrubs" page 699, we find that a wild rhododendron a member of the Ponticum Series native from Ontario to Georgia, Alabama and Ohio was named Rhododendron maximum by Linnaeus. The form with white flowers tinged pink, named Rhododendron maximum roseum by Pursh was considered to be the typical form of the species as distinguished from the botanical varieties album and purpureum which were also named by Pursh.
Rehder on the same page stated that Rhododendron ponticum of Linnaeus was native to Asia Minor, the Balkan Peninsula, Spain and Portugal and that it was probably hardy only to Zone 7. He mentions that its botanical variety, Rhododendron ponticum roseum was named by the botanist Sweet.
More than forty years ago I purchased Rhododendron maximum roseum believing that it was the wild pink variety of Rhododendron maximum, from Andorra Nurseries, at that time the leading American supplier of good rhododendrons. The catalog described it as pink rather than white with pink, and when it bloomed it was rose pink and worthy of being included in any good rhododendron collection.
Then one day Dr. Clement Bowers told me it was not a wild type but a hybrid and I found this confirmed in his "Rhododendrons and Azaleas" on page 357 where he stated it should be correctly called 'Ponticum Roseum'. When David Leach's "Rhododendrons of the World" was published, I found on page 472 that he also considered it a synonym of 'Ponticum Roseum' and that on page 484 he described 'Ponticum Roseum' as a pinkish clone, a hybrid of Rhododendron ponticum. Neither Bowers or Leach ventured to say what other species was the other parent, nor did they even attempt to guess how long ago it was introduced or where or by whom.
In a foolish attempt to avoid the confusion of the names, I quite improperly labeled my plants "Andorra Pink." Later I wanted to purchase more plants but Andorra Nursery had gone out of business and I could not find either 'Maximum Roseum' or 'Ponticum Roseum' in any nursery. Finally in 1960 1 found 'Maximum Roseum' listed by James Wells in Red Bank, New Jersey. I secured several plants for the Tyler Arboretum which grew well but which were very slow to come into bloom. When they did bloom, it was in the season just after the ironclads and long before Rhododendron maximum or my former 'Maximum Roseum'. Not only that, they were not the same color but a much paler pink. So I began to wonder which plants were which and the more I wondered and the more I asked my rhododendron friends, the less I knew.
Then one day I saw a late pink rhododendron listed under the strange name of 'Maxroseum' by Westbury Nursery on Long Island. I was told it had turned up in a shipment of collected plants from North Carolina. I thought this might be the wild variety of Pursh so I bought a plant to try. It did not fit the Pursh description but it was a good late pink somewhere between the two I already had. When I reported this to the nursery I was told that perhaps it was, after all, a hybrid that had got mixed up with the collected plants. It is, apparently, a hopeless job to try to trace its origin.
These last few years I have become more interested in these plants because a series of hybrids made at Swarthmore College in 1953 and 1958 began to bloom. In the hopes of producing some late blooming Rhododendrons that would make a good display at Commencement time, the second Monday in June, Rhododendron maximum had been used as the seed parent. The pollen parents had been red or deep pink Iron-Clads, such as 'Charles Dickens', 'Dr. Dresselhuys', 'F. D. Godman', 'H. W. Sargent', 'Henrietta Sargent' and 'Mrs. C. S. Sargent'. The exact parentage of these old varieties is not known beyond the fact that Rhododendron catawbiense and Rhododendron arboreum and probably also Rhododendron ponticum had been used.
The flowers of some of the resulting hybrids more or less resembled the two 'Maximum Roseum' and 'Maxroseum', but the flowers of others did not resemble any of them. This is true also of 'Midsummer' a variety raised by John Waterer, Son and Crisp and said to be a R. maximum hybrid. It blooms in Swarthmore in mid-June somewhat earlier than most of the varieties I have been discussing. Watching these seedlings evidently opened my eyes, or improved my observation, for this past June and early July I began to notice similar flowers on big rhododendrons planted along the roadside fence lines on private estates. Not over three miles away on Route 250 between Wallingford and Media, there were rhododendrons 10 x 15 feet high and across that look at least half a century old. The flowers were very similar to, or perhaps identical with those of my puzzling plants. About ten miles further away on Route 320 between Villanova and Conshohocken I noticed even larger plants with similar flowers.
The plants may have come from England or Holland long before Quarantine 37 was enacted in 1919 and therefore I would suppose they were varieties well known in Europe in that era. But how could the names be traced? The land on which they are growing has probably been subdivided or has changed owners half a dozen times.
I am writing in such detail in the hope that some of the older rhododendron growers may have some recollection of the late blooming forms of years ago. Or perhaps I can interest younger members of the Rhododendron Society enough so that they will ask the owners of these plants to give them some cuttings, so that some of the varieties may be more widely tested. Any rhododendrons that bloom as well as these do in summer, long after the main season of rhododendron bloom, certainly deserve to be propagated and reoffered by nurseries.