The Knap Hill and Exbury Strain of Azaleas
G. H. Pinckney
John Waterer, Sons & Crisp, Ltd.
The Nurseries, Bagshot, Surrey, England
I was most interested in Dr. J. Harold Clarke's excellent article on "Some Trends in the Development of the Knap Hill Azaleas" in the Quarterly Bulletin of the American Rhododendron Society of the 15th, October, 1952, and would like to confirm and comment on many of his observations.
It is true no records appear to be available of the late Anthony Waterer's hybridization, but without doubt the original Mollis and japonicum hybrids were greatly improved by the addition of calendulaceum and occidentale blood.
Dr. Clarke has very rightly indicted those English growers who are said to have led American purchasers to believe that many of the named clonal varieties will come so true from seed that it is no longer necessary to propagate asexually. If seed and un-flowered seedlings are sold under this guise it is both contrary to the ethics of our Rhododendron and Azalea Association, and completely misleading to the American azalea growing public. With generations of hybrids in the background there can be no guarantee as to what the seedlings will turn out to be, and much variation is bound to appear.
Undoubtedly Mr. Lionel de Rothschild of Exbury achieved more in the improvement of the Knap Hill Azaleas than any one else in England. From some of the most recent hybrids we have had on trial at our Bagshot Nurseries for several seasons we have selected for colour, size of flower and vigor, several varieties which we have named. These are, in our opinion, some of the finest forms of this grand race.
The loose trusses of outstandingly large flowers have a richness and brilliance of colour as well as a wide range not seen elsewhere. In many varieties the flat, open petals are recurved, and in some instances frilled along the edges.
These have been propagated by us vegetatively, and were shown at the Chelsea Flower Show, 1952, for the first time, when several varieties were selected by the Royal Horticultural Society for trial at their gardens at Wisley, Surrey. It is hoped that these named new varieties will appear in the 1953 Azalea Handbook of America.
There is no doubt that in subsequent years many other seedlings will be named, but before a name is given greater discrimination should first be used in ascertaining that the seedling is a definite improvement on its predecessors.
I feel that if all growers were more particular in eliminating those varieties superseded as no longer worthy of garden merit as soon as possible, the public would he better off in being able to select their plants from a smaller and choicer list than now meets the bewildered amateur eye.
In qualification, however, of this opinion, such attributes as suitability to climatic conditions have to be taken into consideration, for example several of the R. catawbiense hybrids--long discarded in this country--are still widely grown in the Northern States where many of our newer hybrids would not succeed.
On page 57 of the Azalea Handbook, 1952, issued by the American Horticultural Society under the heading "Knap Hill Group," the following sentences appear: ". . . Many have keen named only recently. However, in accordance with British practice some of these names are not the names of clones propagated vegetatively but are hybrid group names for seedlings of a particular selected female parent supposedly self-pollinated. Individual plants under such names may therefore vary widely, and in those instances the description given is merely that of the female parent..."
With due respect to the Editorial Board this is misleading, and is not an authorized British practice, although, as mentioned earlier in this article, it has regrettably occurred. Hybrid group names, according to the Rules laid down by our Association, can only be given to primary species crosses. Even their progeny has noticeable variation, a good example being griffithianum x fortunei = R. 'Loderi'.
R. 'Loderi' has thrown many forms, the best of which have been recognized by being given varietal names. It must be remembered, however, that this cross was a result of crossing selected forms of these two species, and it is by no means certain that inferior forms, which do occur, would produce a 'Loderi'. To emphasize this point, R. 'Kewense' = griffithianum x fortunei raised at Kew Gardens, England, can he cited.
Vegetative propagation, therefore, will, I think, always appeal more to the discriminating buyer as it is obvious that seedling from any selected parent, itself a hybrid of very mixed parentage, cannot possibly reproduce itself true from seed.
I again agree with Dr. Clarke that the average run of these seedlings is very good, but they should be carefully selected in flower before being sent out as Knap Hill varieties, since some will be found to be no better than the older hybrids.