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Journal American Rhododendron Society

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Dr. Glen Jamieson ars.editor@gmail.com


Volume 30, Number 1
Winter 1976

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A Game of Chance
H. J. Slonecker, Milwaukie, Oregon

        It has been suggested that my experiences and my success, or nearly lack of same, in raising seedlings from certain crosses made between parents of the Knap Hill strain of azaleas might be of interest to the membership. Perhaps a parallel can be drawn between these experiences and possible hybridization, carried on in the future, using rhododendron parents of a like complex ancestry.
        To emphasize the complex nature of the blood lines of the Knap Hill strain of azaleas, let's briefly review the history of their development. It was all started at the Knap Hill Nursery in England just after the middle of the 19th Century by Anthony Waterer, Sr. He started with the Chinese R. molle, various selected forms of the American R. calendulaceum and some of the best of the Ghent hybrids. Later he introduced R. japonicum, our western R. occidentale and the fine eastern R. arborescens into his hybridization.
        The Ghent hybrids were started in Belgium in about 1825 using R. calendulaceum, nudiflorum, roseum, speciosum, viscosum, molle, luteum, canescens, cumberlandense and others. This illustrated the great variability of blood in even the earliest of the Knap Hills. Waterer crossed and re-crossed prolifically during his lifetime and it is speculated that he raised at least 10 generations of azaleas. He produced some wonderful seedlings of more brilliant color with larger flowers of more substance than any other hybrids up to that time. Very few of his seedlings were named during his lifetime and apparently none whatsoever were released to the trade.
        After his death in 1897, his son Anthony Waterer, Jr., carried on the work and added innumerable generations of deciduous azalea hybridization. He maintained the best of his father's seedlings and added many of his own. He died in 1924.
        About 1922 Lionel de Rothschild of Exbury Gardens was able to obtain some of the best of the Knap Hills from Anthony Waterer, Jr. Mr. Waterer was very reluctant to give them up, but did so apparently because there was no one in his family prepared to carry on the work.
        Rothschild immediately set about hybridizing on a large scale using the best of the Knap Hills, the best R. occidentale hybrids, R. japonicum, and R. molle x R. japonicum. He carried on this work for over 20 years and the resulting Exbury race is known for richness and brilliance of color as well as a much wider range of colors than ever seen before. He was able to double the size of the flowers. They were flat faced, or in some cases with recurved petals, and in some instances with frilled edges. They are without doubt some of the finest deciduous azaleas in the world.
        In the mid-1950's, I was able to obtain a number of the Exbury azaleas and three Knap Hills. Up to that time we had to be satisfied with 'Altaclarense' and Mollis azaleas for yellow color in deciduous azaleas. The Mollis yellows left much to be desired and there was much activity in trying to produce better yellows just as there was in producing better yellow evergreen rhododendrons. I was much impressed with the Exbury yellows available at that time, especially 'Klondyke', an orange tinted yellow, and 'Hugh Wormold', with rather small flowers, but the most intense yellow of all.
        I was also much impressed with 'Marion Merriman' which was produced at Knap Hill in the early 1920's, but which apparently was not obtained by Rothschild. When I first heard of it in the 40's, it was known as the best of the yellow Knap Hills and was rated as one of the best yellows in the world. It had a large flower of a very pleasant and good yellow color. I realized that it was probably far enough apart from the Exbury strain of yellows that a mating with the latter might produce interesting results if enough seedlings could be raised.
        The laws of genetics are such that an F, cross between two species invariably results in progeny that are more or less intermediate between the parents. As you advance into the crossing of the hybrids with more complex blood lines, the progeny will be more varied especially if every seed out of cross is raised. The one dropped seed may be the ''break" of the cross, the outstanding hybrid that is lost to the world.
        I had read that the Dutch in the early 20's had raised about 20,000 seedlings from a cross between two very inferior hybrids by present standards, of very complex blood lines. Of these 20,000 seedlings, one was named 'Earl of Athlone', and another 'Britannia'. They far outstripped any hardy hybrid reds of those times and when shown in British flower shows of the middle 1920's caused a sensation. Both received an F.C.C. from the Royal Horticultural Society. Other named plants of record out of this cross were 'C. B. van Nes', 'Dr. W. F. Wery', 'Langley Park', 'Van Nes Glory', and the old warhorse 'Unknown Warrior', very inferior by present standards. These five drop off in quality very fast from the two best out of the cross. The other 19,993 plants should have made a nice warm fire.
        I had been on very friendly terms for many years with Art Wright, Sr., the founder of the Art Wright Nursery in my neighborhood. He was a keen plantsman and we spent many hours discussing horticultural subjects. He had produced some of the better Mollis azaleas of this country, particularly in the reds. The large planting of red Mollis at the Crystal Springs Island Rhododendron Garden in Portland contains some of his productions and were given to the garden in one large block. There is one in this planting he must have missed as I have been watching it for years and believe it to be the finest red I have seen. It should be named and propagated. He was also hybridizing rhododendrons and I was able to furnish some unusual pollen used in some of his crosses. Art Wright had a very discerning eye for plants of unusual merit and would discard everything that was clearly not superior.
        I told him of my thoughts on creating better yellow azaleas and he agreed to raise every seed of the crosses I was interested in making. This meant a tremendous sacrifice on his part as it would mean less time and nursery space for his own horticultural activities.
Three crosses were made: 'Hugh Wormold' x 'Marion Merriman', 'Klondyke' x 'Marion Merriman', and 'Hugh Wormold' x 'Klondyke'. About 5000, 2000, and 3000 seedlings respectively were raised of the three crosses. Of the first named cross at least 50 percent were of very inferior quality and nearly all of the remainder were slightly inferior to, or no better than, the parents. Only 17 were picked out as superior or possibly superior. Thirteen were named and of the four unnamed, kept for further evaluation, none has been deemed worthy of naming and have been mainly discarded. Of the 13 named, only eight now seem worthy of having been named. That is a ratio of one good plant in 625 seedlings. If we had raised only 624 seedlings, I might have missed getting that one good plant.

R. 'Clackamas'
R. 'Clackamas'
Photo by Howard Slonecker

        Art and I had watched the 'Klondyke' x 'Marion Merriman' seedlings for about three years from the time they began blooming and had about given up getting anything worthy out of them. One day when I dropped by Art said, "You know there is one plant in that horrible mess that looks a little better.'' It was the runt of the lot and one of the last to produce flowers. It has been named 'Clackamas'. It is the only one that was kept out of the cross and it is not yellow. That is a ratio of one good plant in 2000 seedlings. It remains a slow growing plant. The original plant is now about 31/2 feet tall as compared to 'Yaquina' which is out of the 'Hugh Wormold' x 'Marion Merriman' cross and is 9 feet tall, although of the same age.
Of the last of the three original crosses, only two seedlings were named and one of those is now proven to be of dubious merit in comparison to its parents. It would be an under
statement to say that 'Klondyke' was a poor parent. 'Clackamas' seems to be the only superior plant out of 5000 of its seedlings and it did not come yellow as originally was hoped when the cross was made.
        People ask me why I do not, or if I am, going on with deciduous azalea breeding. Firstly, I do not want to unless about twice as many seedlings are raised per cross as previously. Any volunteers to do what Art Wright did, but on at least twice as big a scale? The line forms to the right.
        Secondly, the other colors have wonderful representatives and it is hard to imagine improving such as 'Cecile', 'Orangeade', 'Ginger', 'Princess Royal', 'Scarlet Pimpernel' and several others as well as my own 'Yachats', if modesty will allow its inclusion. In my opinion, further increase of flower size alone would be a doubtful improvement.
        Undoubtedly, someone will emerge with a fertile imagination as to where improvements can be made and with a gambling nature conducive to raising 10,000 seedlings per cross with only a chance of producing a few improved plants. Or perhaps someone will figure out how to program a computer so that it would tell him how to reduce the odds in this game of chance.


Volume 30, Number 1
Winter 1976

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