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Helleborus thibetanus Franchet
It is very exciting to report that this virtually unknown species is now in cultivation in Britain for the first time - albeit only as seedlings so far. Until recently this plant has been represented by no more than old herbarium specimens, tantalising photographs of which have occasionally been published. Seed was almost certainly sent to Veitch's nursery by the plant collector William Purdom, but the plant never became established in cultivation.
In recent years several botanists have sought it without success possibly, as we now know, because it is in growth for only a few months of the year and becomes obscured by taller vegetaion after flowering. However we have now received not only a first hand description of the plant and its habitat, but photographs taken of colonies in the wild. This has been made possible by the generosity of Japanese botanist Mikinori Ogisu who followed the clues in Pere David's diaries to Moupin in the Sichuan province of China where he discovered several colonies of H. thibetanus in the area where Pere David himself first found the plant over 120 years ago.
Description
A deciduous perennial reaching 12-16in (30-40cms), sometimes 20in (50cm), whose leaves are visible for a surprisingly short time, emerging rapidly when the flower stems are well developed and reputedly dying down completely by the end of July. The leaves are pedately divided, normally with the three central leaflets unduivided and the outer two subdivided into two lance shaped segments making a total of seven divisions; they are edged with distinctive saw-like teeth. The flowers are around 2in (4.5-5.5cms), sometimes 21/2in (6cm), across and open in March in the wild. They are generally bell-shaped with pointed petals, white at first then fading almost immediately through dark-veined pink to green as the flowers age and the seed ripens. The bracts are noticably well developed and distinct in being much large than those of other species. In the Moupin population about half the flowers have two carpels and half have three. The seed ripens in early May, the seed seems to produce no visible cotyledons when it germinates.
Distinctive features
It has generally been the impression amongst botanists that this species has only two carpels and for this reason it has been separated from otherwise similar species and placed in its own section of the genus, Dicarpon. It now seems that this is by no means a constant feature, at least in Moupin but the fact that this species produces no cotyledons indicates that it is still sufficiently distinct to retain its own individual section in the genus rather than be incorporated into the Helleborastrum section with the other stemless species.
It is distinguished from other similar species by its distribution, its flower colour, its short period in leaf, its bold foliage, large bracts and its relatively few carpels.
Natural distribution and habitat
This species is known only from the Chinese provinces of Gansu, Shaanxi and Sichuan. In Moupin in Sichuan province, there are several colonies in the area where the plant was discovered by Pere David. Here it grows at a height of 1900-2000 metres in damp, rocky clearings in scrub with up to 40% of the plants shaded by luxuriant growth of Mattucceia struthiopteris. Other plants with which it grows include astilbes, hemerocallis, Fritillaria davidii and Petasites sp. and seedlings of Cunninghamia lanceolata with Salix magnifica and Hydrangea heteromala nearby.
Cultivation
It seems clear that in the wild H. thibetanus prefers a damper habitat than most species but in gardens a rich woodland soil that doesn't dry out should be ideal.
In gardens
Fresh seed was sent to Britain in 1991 and three or four growers now have seedlings developing so there is a good chance of this plant at last becoming established in cultivation. However, as yet we have few clues as to its vigour or its generosity with seed so it could be many years before plants are available.