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Journal American Rhododendron Society

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Dr. Glen Jamieson ars.editor@gmail.com


Volume 11, Number 2
April 1957

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Some Facts About R. orbiculare
G. G. Nearing, Ramsey, N. J.

        The close-up photograph on p. 49 of the January Quarterly of the Society may be correctly named R. orbiculare, but does not look like it. The length of the rhachis is about right, but there seem to be only five flowers, while the botanical description of the species calls for seven to ten. Of course, in any plant there will he some trusses with fewer flowers than normal, but a photographer will almost invariably pick out the best filled truss on the plant to photograph. So we must assume that this represents the fullest truss.
        It looks like what could be expected from R. orbiculare pollinated by 'Temple Belle', because the truss or R. williamsianum, the other parent of 'Temple Belle', is three to five flowered. More important, if you can compare the shake of the flower with those illustrated in The Species of Rhododendron p.279, you will see that the base of the corolla should lie broader, the lobes shorter than in the photograph. Of course plants of the same species in nature do vary considerably, and moreover the artist who made the drawing had probably never seen a living plant of this species in flower, so we must not be dogmatic. But this photograph very likely represents a chance hybrid. The same may he said of the illustration in the 1956 yearbook, p. 80. I have seen in England old plants which were undoubtedly grown from seeds that cane from China, and the flowers do not look like those in either photograph.
        I have repeatedly sown seeds marked R. orbiculare, but have seldom germinated anything resembling that species. The reason is obvious if you know the facts. The species is confined in nature to a small area in western Szechuan between Mupin and Tatsienlu. So far as I can discover, no collector has gone into that section since E. H. Wilson, and his last expedition there was made about half a century ago. From the seeds he sent home, only a few plants were ever raised to flowering size, because R. orbiculare is difficult under cultivation, and the survivors of those few do not flower freely. Most plants marked R. orbiculare have been grown from seeds gathered on those plants or their offspring.
        But most rhododendron seeds offered for sale or exchange, come from flowers which took whatever pollen the bees brought. There was an exception. For several years Lionel N. de Rothschild had a number of species pollinated by hand with pollen from authentic plants of the same species, and these seeds were distributed by the Rhododendron Association. They proved as reliable as seeds collected in the wild from plants nn their native soil. But at present the overwhelming hulk of species seed is chance pollinated; therefore unless a group of plants of the same species stand to-ether in an isolated position, the seeds will he mostly hybrid, and anyone who grows plants from them should not call the plants by the name of the species unless they carry all its botanical characters.
        The illustration of R. orbiculare on P. 50 of the Quarterly, January, is also misnamed. I remember the plant very well, and it had a label on it in 199 reading "Aucklandii x orbiculare." Of course that label may have become illegible, and the photographer may have made a bad guess.
        One way you can be sure it is the hybrid and not the species is to glance at the truss. "The Species of Rhododendron" gives the length of the rhachis as 2 to 3 cm. It is easy to see that the trusses in the illustration have a rhachis ten times that long. I have a Kodachrome close-up of this same plant in which the long rhachis can be seen plainly, also a Kodachrome showing about the same view as your photograph, though the bloom that year was not nearly so heavy.
        There are other differences, especially the shape of the flower. An orbiculare flower is deeply bowl-shaped, with the lobes small and flaring only slightly. The hybrid has a corolla tapering slightly toward the base, and the lobes larger and more widely flaring, or even slightly reflexed. The leaves are also different, those in the photograph being at least a third too long for orbiculare.
        The R. orbiculare at Exbury, of which I have a good Kodachrome shot, is the finest I saw in England, because the color is a fairly good pink, while R. orbiculare has ordinarily a sickly purplish tint. On the strength of this one specimen, which looks suspiciously like 'Temple Belle' Rothschild had R. orbiculare rated more highly than it deserves. 'Temple Belle' is much more often grown, because, for one thing, it is growable, while R. orbiculare is rather difficult and not nearly as hardy.
        It would be only fair to explain that the photograph of that really glorious plant at Bodnant, represents a hybrid.
        Since R. orbiculare is reluctant to grow and even more reluctant to flower, it is a rarity, and most of the authentic plants from E. H. Wilson's seeds stand as single specimens, more miles from the nearest of their kin than any bee is likely to fly. Consequently, unless someone goes to a great deal of trouble and applies authentic pollen to an authentic seed parent, any seed named R. orbiculare will be mislabeled. You can expect from them only chance hybrids.
        Anyone unfamiliar with the problems of breeding might think that a part of the seed at least would be genuine, because a certain amount of the plant's own pollen would find its way to the pistil of each flower. I am not sure how it is with orbiculare, but many species refuse their own pollen, and many, although the pollen may cause seed to set, are so weakened by inbreeding that the seedlings fail to grow. Add inbreeding to natural miffiness, and you have a combination which will probably prevent any grown plant of orbiculare arising from self-pollination.
        The same is true of a number of other Rhododendron species. But in most cases there is plenty of authentic material with which to compare the hybrids, which in consequence are easily weeded out. Such things as R. wardii and its subspecies, which have been collected by almost every explorer who ever entered western China, vary considerably, but can be compared with plants known to be grown from Chinese seeds.
        R. williamsianum has been collected only on a single mountain in the same area where R. orbiculare is found, but its history under cultivation has been remarkably different, since it is rather easy to grow, and because of its great beauty has been propagated assiduously both by seeds, which germinate well, and by cuttings, which root easily. Hybrids such as 'Temple Belle' (williamsianum x orbiculare) are easily grown and abundant in the south of England, and it is only natural that chance hybrids from them, which look somewhat like orbiculare, can be expected to survive, while orbiculare seedlings, given the same conditions and the same care, will probably die. Consequently it is almost certain that the great majority of plants grown under the name R. orbiculare are not that species at all, but hybrids.


Volume 11, Number 2
April 1957

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