QBARS - v26n4 R. Cinnabarinum Series

R. Cinnabarinum Series
G. Guy Nearing, Ramsey, N. J.
(Transcribed from Lecture Given to Tappan Zee Chapter)

This evening I am going to talk about the R. Cinnabarinum Series. This is one of the most celebrated groups of rhododendrons, very different from the ordinary rhododendrons. In England where R. cinnabarinum and its close relatives are to be found to be hardy, it is highly prized and they have developed many hybrids comparable in number to those of R. griersonianum and R. griffithianum (not as many as that but a great many). Most of its species and hybrids are awarded three and four stars of merit. Unfortunately, R. cinnabarinum itself is not hardy enough to survive with us in our climate. The entire Series is so tender that we simply haven't anything around us that belongs to it but I am sure that in time it will be possible through hybrids to achieve the same beauty in hybrid forms. This is a slide of R. cinnabarinum taken in the south of England and another from Bodrrant in Wales. The foliage is very shiny and glowing. It belongs to the lepidote rhododendron group and it is more showy I think than any of the other scaly leaved members.

R. 'Lady Berry'
FIG. 88. 'Lady Berry' showing the pendant,
tubular flowers characteristic of
Cinnabarium Series offspring.
Photo by C. Smith

Here is a hybrid of R. cinnabarinum , 'Lady Chamberlain'. It is the cross, R. cinnabarinum war. roylei x 'Royal Flush'. It is planted in gardens in the south of England in great numbers. 'Lady Chamberlain' is really magnificent and is one of the most spectacular of rhododendron hybrids. It is quite different from other rhododendrons. The flowers are trumpet shaped and are drooping. The colors are very pure, mostly scarlet, orange and yellow. There are some that have interesting combinations of purple in the flower, which isn't the ordinary shade of purple but is an overlay of purple which gives a strange effect. Here is another slide of 'Lady Chamberlain' and this one taken at Exbury. Rothschild did a lot of work with R. cinnabarinum hybrids, especially 'Lady Chamberlain' and this slide gives you an idea of the general appearance. Because the flowers droop and have that trumpet shape they give an effect different from all other rhododendrons of the scaly leaved group. Here is 'Lady Chamberlain' in Kew Gardens. As you can see it's really a brilliant pink where R. cinnabarinum itself is more of a cinnabar red. 'Lady Rosebery' is similar but has more yellow in it. It too is also highly prized in England.
One of the most popular of the R. cinnabarinum hybrids is 'Royal Flush'. It is very pink, free flowering and a shapely plant. I had 'Royal Flush' in my cold pit but it died. It couldn't stand the climate. A related species is R. concatenans . David Leach in his book, "Rhododendrons of the World", claims that R. cinnabarinum , R. concatenans and R. xanthocodon should not be considered as different species but should be combined into one, since the natural hybrids and the variations in all three species merge imperceptibly one into the other. You cannot find any line of distinction between these three species. R. concatenans is typically orange-salmon in color but there are also yellow and pink shades. It also has drooping flowers.
Another of this group is R. xanthocodon and it is because of R. xanthocodon that I have given so much consideration to this Series. R. xanthocodon is a good yellow. I have a plant of R. xanthocodon . I don't know, or remember where I got it but it has been growing for years in my bed in the open. It is just about perfectly hardy, not completely, as it will sometimes lose a few buds in a very bad winter. Generally it opens all or nearly all its buds. it is a dwarfish plant which doesn't agree with the typical R. xanthocodon but it is exactly like the illustration in Dave Leaches' book. The flowers of R. xanthocodon are usually shaped like R. cinnabarinum but in this case it has a shorter flower and is more ball shaped. Since we have a hardy R. xanthocodon there is every reason to hope that we can get hardy forms of the other two species. Here is a slide of R. xanthocodon which is three feet high and carries its foliage nicely. It has been blooming for me for several years, ever since 1964. It looks a little something like R. keiskei . In itself it is not too worthwhile working with but it shows the hardiness possibilities. What I intended to do was to get a plant of 'Royal Flush' and to use its pollen on this plant, then perhaps if the result was not hardy enough, to cross it with R. carolinianum someway, and to mix up the crosses until I got the hardiness into R. cinnabarinum or one of R. cinnabarinum hybrids. My 'Royal Flush' died in the pit so I am growing cuttings of the hardy R. xanthocodon so other people can use it in hybridizing. The Cinnabarinum Series is not too easy to hybridize. It will not hybridize easily with other scaly leaved rhododendrons. It seems to have another or different system of genes than the others.
Then there is another plant of this series R. keysii that has a very odd flower, very narrow, whose color is red with a yellow edge and yellow center. It is quite interesting and quite different from most other rhododendrons. Here is a plant of a cross between R. cinnabarinum x R. keysii known as 'Cinnkeys'. It is quite a striking plant.
Unfortunately I have comparatively few slides of these as they are difficult to come by. They are not hardy in this climate and none of the hybrids have been found to be hardy. People have paid very little attention to this group and I think the entire R. Cinnabarinum Series ought to get a great deal more attention. I think in time we will be able to get hardy forms of flowers very much like the color of R. cinnabarinum in hybrids, but perhaps that is just a hope.