JARS v40n3 - The Delightful Glaucophyllums

The Delightful Glaucophyllums
Felice Blake
Kallista, Victoria, Australia

Those gardeners who appreciate the subtleties of the smaller rhododendrons will find some most delightful species in the Glaucophyllum Series (Subsection Glauca in the new classification) to enhance their gardens. Although the Glaucophyllum Series contains but a relatively few species, among them are several of the finest and loveliest shrubs that one could wish for.
The glaucophyllums come from the Himalayan regions of Sikkim, India (Arunchal Pradesh), Nepal, Bhutan, Assam, Upper Burma, the southern and eastern parts of the Chinese province of Xizang (Tibet), and the Chinese province of Yunnan. They are small to medium shrubs, with brown flaking bark and evergreen foliage. Lepidotes with the characteristic scales on the undersurfaces of their aromatic leaves, they are very glaucous as one would expect from the name. Scales are also present on the corollas of some species. The charming flowers are generally campanulate, although sometimes tubular-campanulate, in varying shades of yellow, greenish yellow, pink, rose, plum or almost cerise, and white, with white flowers being the more unusual.
If we still think in terms of the Glaucophyllum Series, then we would include the Genestierianum Subseries, with the two species R. genestierianum and micromeres , but if we follow the new line of thought, we find that R. genestierianum is in a subsection all on its own - Subsection Genestierianum. This fact brings to the fore the highly individual characteristics of this species. It is a most unusual plant which can be easily recognised by its distinctive clusters of purple flower buds covered with a grape-like bloom. At this stage one could not be blamed for thinking that the shrub had made a mistake and got entangled with a grape-vine! Actually when the buds burst into flower, they can be a wee bit disappointing. The flowers are very small for the size of the shrub which is quite tall as compared with its near relatives. I used to grow this one in my former garden at Mt. Dandenong, but when we moved to a smaller property, it was one of the many rhododendrons left behind, which I now regret. It always was a talking point! The other rhododendron formerly in the old Genestierianum Subseries, R. micromeres , has now found a new home in Subsection Boothia which leads one to think that the "name-changers" have been busy.
But back to the glaucophyllums - the type species, R. glaucophyllum was first discovered by Hooker (as R. glaucum ) in May, 1849, in the Sikkim Himalayas, and since then by various other collectors in Sikkim and also in Nepal and Bhutan, so it is widely spread. As one would expect, therefore, the species is quite variable resulting in it having both admirers and detractors. It is one of those species which has both ordinary and really lovely forms. It is up to the grower to seek out the best forms, and acquire them in flower, as some of the poorer forms with very small flowers are scarcely worth growing. At its best it is a deep rosy pink, but some of the lighter pinks can be charming. Although we usually tend to think of R. glaucophyllum as one of "smaller" rhododendrons, it can attain a spread of five feet in due course. There is also a white form discovered as recently as 1971 by Beer, Lancaster and Morris in Nepal. My plant, which I imported some seven years ago from Scotland, so far seems to be much smaller growing than the pink forms and with smallish flowers. There is, however, a named cultivar 'Len Beer' which no doubt is the best form so far grown. This would be the one to seek out. The form var. tubiforme differs in its tubular-campanulate flowers.

Perhaps the most outstanding species in the Series would be R. luteiflorum , a most beautiful bright clear yellow, flowering early in the season which makes it doubly valuable, unless you are in a very frosty area. This species was for many years classified as a variety of R. glaucophyllum , but was finally given specific status in 1978. It is certainly very, very different from R. glaucophyllum ; different in the shape of the leaf, different in the flower, and coming from a distinctly different area. It was first discovered by Kingdon-Ward in North Burma in 1953, so is of comparatively recent introduction. R. luteiflorum is certainly a "must" for everyone. It is among the most exquisite yellows in the smaller rhododendrons. So far it does not seem to grow nearly as large as R. glaucophyllum , not more than two feet high in ten years, in our climate. It has, however, the reputation of occasionally dying for no apparent reason. As it is fairly easy to raise from cuttings, I keep some small plants coming on in case that fate befalls any of my plants in the garden (it has happened once - why I do not know). Surplus small plants can always find new homes.

Another beauty in the series is the charmer, R. charitopes , discovered by Farrer in 1920, in the Shing Hong pass in northeast Upper Burma. In his field notes he wrote "...a particularly charming plant of nine inches to a foot, very copious with 3 (very rarely 4) bloomed inflorescences. Flowers of a clear apple-blossom pink, but flushed more warmly in their upper lobe and speckled with crimson, and with a deep-rose tube." The name "Charitopes" means "graceful of aspect" and that truly sums up this delightful rhododendron. Many of us tend to look upon the glaucophyllums as rather larger editions of the campylogynums, and we are in good company - Farrer at first thought R. charitopes a dwarf of the Campylogynum Series. It is not quite so easy to propagate as some others, hence it is not so widely available as it deserves to be. Farrer also found a natural hybrid of R. charitopes x R. charopoeum (now classified as a form of R. campylogynum ) growing alongside its parents, which unfortunately was not introduced. This was on Farrer's last journey, as he died in Upper Burma in 1920.
Closely allied to R. charitopes is R. tsangpoense (Dr. Cullen considers it to be a subspecies of R. charitopes ). It was discovered by Kingdon-Ward in 1928 on the Doshong La in south east Xizang (Tibet). This species has pink, or pinkish purple flowers, and groups well with others in the series. To me it is not so attractive as the lovely R. charitopes , but then again there are so many forms of species, it always seems that one must seek out the better forms.
R. prunifolium is another one collected by Kingdon-Ward, in north east Burma. It has been given specific status, although for years it had been considered a variety of R. tsangpoense . It is now considered that it differs from that species by some authorities and is closer to R. brachyanthum . It has plum-purple to cerise flowers, late in the season.
Considered by some to be close to R. charitopes and by others close to R. brachyanthum var. hypolepidotum is R. shweliense , with its yellowish flushed pink flowers. This one was collected by Forrest on the Shweli-Salween divide in west Yunnan. It has the reputation of not being too easy to grow, so it can present a challenge to the keen gardener. Have we got the genuine species? Opinions seem to differ on that point. Some plants masquerading under the name of R. shweliense appear to be hybrids of R. glaucophyllum . I hope my plant is correct!
Some people are inclined to think that R. brachyanthum and its variety hypolepidotum are scarcely worth growing with their rather small pale yellow (or greenish yellow) flowers. I do not really agree with this. I find that even non-rhododendron visitors always make comments on the rather unusual little shrub, very low growing with me, with pale yellow wide open bells held well above the foliage on long pedicels. The species was first discovered by Abbe Delavay about 1886, in Yunnan, but was not introduced until 1917, and then by Forrest. It seems to come from a fairly restricted area. However, the var. hypolepidotum which was first discovered by Abbe Soulie in 1903, in south east Tibet (now Xizang province of China), comes from a wide spread area including Yunnan and Upper Burma. The variety, which differs from the species only in having more densely scaly leaves, is also the more commonly grown.
It is interesting and revealing to check back on some of the changes in thinking on the classification of species. Back in 1947 we can note from the second edition of The Species of Rhododendron (Ed. J.B. Stevenson), which was for so many years the rhodoholics "Bible," that the Glaucum Series, as it was then termed, included the following species: R. brachyanthum , charitopes , charitostreptum (now synonymous with R. brachyanthum var. hypolepidotum ), genestierianum , glaucum (now R. glaucophyllum ), micromeres , hypolepidotum , pruniflorum , pemakoense (believe it or not!), sordidum (now synonymous with R. pruniflorum ), shweliense and tsangpoense . Personally I find it hard to credit that R. pemakoense could have had anything in common with the glaucophyllums , but there it is in black and white!
The glaucophyllums do not seem to have been used very extensively for hybridising - probably the best known would be 'Rosy Bell', a very old hybrid between R. ciliatum and R. glaucophyllum , which gained an A.M. way back in 1894. It is still regarded quite highly, but does need constant guard against rhododendron rust, particularly in autumn and winter. It has quite large pink bells and to me is a charming addition to the garden. A number of other hybrids do not appear to have been released commercially. However a recent hybrid between the white form of R. campylogynum and R. luteiflorum named 'Merganser' is now listed by a well-known Scottish nurseryman and described as "like a large campylogynum but with yellow flowers". Sounds exciting doesn't it? R. luteiflorum has also been used as the seed parent with R. keiskei 'Yaku Fairy providing the pollen, to form another exciting hybrid named 'Elfin Gold'. This one hails from England. So it would seem that the modern hybridizer is attuned to the worth at least of R. luteiflorum as a parent. Perhaps the amateur could join in and try to create more interesting variants, perhaps such as those natural hybrids that both Farrer and Kingdon-Ward found in the wild. The possibilities would seem to be endless.
Many years ago I was given a tiny inch high seedling of what was thought to be R. luteiflorum from Scottish seed. It soon became apparent that the bumble bee had been at work, as the leaves lacked the characteristic glaucous backing. In time, the plant flowered and turned out to be quite an outstanding hybrid, with a many flowered truss of flame flowers typical of the campanulate shape of R. luteiflorum , but with larger leaves, light green on both surfaces. In eighteen years this shrub has grown to about four feet by three feet, flowering over an extended season from mid to late winter to mid spring. It always attracts attention, and propagates quite easily from cuttings - the cuttings flowering in about four years. Apart from the lovely flowers, it sports flaking cinnamon bark which looks most fascinating with the sun shining through it.
The glaucophyllums are suited to the large rock garden or peat bed. They are particularly charming in association with the campylogynums, in the shrub border or at the edge of the woodland. It seems to me that these delightful rhododendrons would appeal to all gardeners, and our rhododendron collections would be poorer without them.

With this article, Felice Blake continues her series on various rhododendron subsections. Previous articles include "The Many Faces of Rhododendron Campylogynum" JARS Vol. 39:2, "The Elegant Cinnabarinums" JARS Vol. 39:3, "The Graceful Triflorums" JARS Vol. 40:1.