Breeding Evergreen Azaleas in the Mountains of West Virginia
W. L. Tolstead, Elkins, West Virginia
I have worked with several strains, taxa or species of the Obtusum Subseries over a period of a little more than 15 years. So far nothing that would shock the world has developed, but now I have the gene pool necessary for production of a good, hardy plant for our eastern mountains characterized by extremes of climatic conditions somewhat outside the ecological tolerance of most Obtusums. If there are no linkages, it is largely a matter of time and making the right combinations.
FIG. 9. R. nudiflorum has a wide ranging
habitat from the Carolinas to
Photo by Fred Galle
I have some of Pride's evergreen azaleas, especially 'Nadine' and 'Marjorie'. They flower too early, even before the earliest native, Rhododendron nudiflorum, but seem quite hardy. 'Willy', imported from Scotland, even though it is originally an American clone and used in the Glenn Dale hybrids, is like the above, too early flowering and the buds are injured by frost in October. The same is true of most plants obtained as seed from F. W. Schumacher that were labeled R. kaempferi, but obviously these are not in this taxon alone, probably more correctly a mixture of this species with R. mucronatum and R. obtusum. They have been around here about 17 years and some clones seem very hardy. While they tend to be very early flowering, a few plants with red flowers escape late frosts in May. They have a small, summer leaf that is short and rounded and a much larger spring leaf. These later individuals have possibilities bred with the very late ones, but I have made this cross only this spring (1974).
About 15 years ago a seedling from a stray seed accidentally contaminating a collection from England had hardiness and lateness of flower with early budding in fall. It seems to run out in Wilson and Rehder's key to R. simsii, a Chinese species, and it just could be from a collection on some northeastern Chinese mountain that might not be typical of the distribution of this species generally. R. simsii is widely spread throughout east Asia, the most widely distributed one in the Obtusum Subseries. I now have a number of seedlings derived from this plant.
Wilson and Rehder in the "Monograph on Asiatic Azaleas" say "At its (R. simsii) upper altitudinal limit the leaves are much reduced in size and nearly all fall off in the late autumn".
Another clone called 'Inverwe Pink' from Mr. Peter Cox in Scotland is at least late flowering and early budding, but I am not sure of its hardiness yet. Since it took the import gaff, it might be quite tough. It was outside so far only one winter, hardly a testing year. Its specific identity remains uncertain to me. At any rate it is quite different. It is slow growing. I have a number of seedlings from it too.
A considerable number of plants of R. kiusianum and hybrids of these and second and third generations do not have sufficient hardiness though selections have been made over a period of about ten years. The originals were imported from England as was also R. nakaharai. The latter and its hybrids show early budding in fall, winter hardiness of the wood and very late flowering, somewhat more so than R. kiusianum.
So far I have paid no attention to color of flowers or any other desirable trait. I have been satisfied with what comes and hope especially for success working with the three genetic combinations indicated above: early budding in fall, wood hardiness in extremes of winter cold and late flowering in late May.
Mr. Peter Cox has a chapter on the evergreen, Obtusum azaleas in his recent book. He states here that few species of this series have been a success in Scotland because it never gets warm enough to harden up the wood. This might be the problem here too, and in addition, there is the need to withstand extremes of cold in winter (-15° F). My emphasis on early budding is to give the young flower buds a little more beat in early fall and more time to "harden-up" or mature before the first frosts that occur here on the average October 12. The buds should be showing by August 15 or better yet by August first. The late-flowering trait is needed because of late frosts in spring, and plants should therefore bloom in the last half of May. April and early May are much too early for flowering because the flowers would be killed nearly every year.
Three taxa (R. simsii, 'Inverwe Pink' and R. nakaharai) have the desired genetic combinations already naturally developed in their native habitat in Asia, possibly at the extremes of the ecological range of the Obtusums. It is interesting also to note that our four native azaleas have the same traits looked for in the Obtusums. Nature worked this out in them a long time ago (R. roseum, R. nudiflorum, R. calendulaceum and R. arborescens).
That these three traits are present in two diverse groups of azaleas inhabiting cold parts of their ranges is an interesting case of parallel evolution. That the Asiatic species are not quite up to the extremes of the East American ecological stance lies in the generally more moderateness of the east Asiatic climate.
Most of my worth-while finds came from the United Kingdom because the British have a long record of searching over the world for plants, and the selections made by them in their far northern latitude also fit quite well into our needs here. We do have a climate in these mountains that comes close to being European, not as ideal as that of Britain, but it is quite near that of the central, continental alpine areas of southern Germany and Austria.