Rhododendron sinolepidotum Balf.f.
Rhododendron lepidotum is an evergreen shrub usually growing 50 - 150cm tall, occasionally reaching 200cm[
The plant is harvested from the wild for use as a medicine. It is grown as an ornamental in gardens.
Although no specific mention of toxicity has been seen for this species, all parts of Rhododendron species (including the leaves, flowers and pollen) contain greater or lesser amounts of the toxic compound andromedotoxin (also known as grayanotoxin). Rarely lethal to humans (and used medicinally in some herbal disciplines), this compound causes dose-dependant overstimulation of the central nervous system with symptoms including various cardiovascular effects (mainly low blood pressure and cardiac rhythm disorders); nausea and vomiting; and a change in consciousness. The effects commence shortly after ingestion and last around two days. These effects are also transferred to honey made from the nectar of the flowers. In some parts of the world bees are used to deliberately produce a honey rich in andromedotoxin which is then eaten for its supposed medicinal, hallucinogenic and aphrodisiac effects.
In contrast to humans, many other creatures are more susceptible to the toxin and it has sometimes proved lethal to grazing animals and household pets. Some forms of honeybees are also killed by the toxin (resistant forms of the bee are used for honey production). Bumblebees are not affected, however, and are also more efficient in pollinating rhododendron flowers, so one theory is that the toxin is produced by the plant in order to favour the bumblebee and improve fertilization rates[
E. Asia - Himalayan regions of China (Sichuan, Xizang, Yunnam), northern India, Nepal, Bhutan, northern Myanmar
Forests, scrub, grassy slopes, moorlands, rocks; at elevations from 1,700 - 4,200 metres, most commonly between 3,000 - 3,600 metres[
|Cultivation Status||Ornamental, Wild
Rhododendron lepidotum is a very cold-hardy plant, able to tolerate temperatures down to around -30°c when fully dormant. Although cold-tolerant when dormant, the flowers and young growth of Rhododendrons are very susceptible to damage by late frosts in regions where these are likely to occur after new growth has commenced in the spring[
Rhododendron species generally succeed when grown in a non-compacted, humus rich lime free soil and a position with some shade, preferably light woodland shade. They strongly dislike soils of a dry arid nature, heavy soils or clays[
]. Prefers a peaty or well-drained sandy loam[
]. Succeeds in sun or shade, the warmer the climate the more shade a plant requires[
]. Requires a pH between 4.5 and 5.5[
Rhododendron species are mainly woodland species that grow well in the dappled shade and shelter given by the other woodland plants. They are surface-rooting species with a fibrous root system, however, and do not grow well close to trees that are also surface-rooting, nor do they do well with ground cover or other small plants growing over or into their roots[
Plants form a root ball and are very tolerant of being transplanted, even when quite large, so long as the root ball is kept intact[
Some caution is advised in the medicinal usage of this plant - see the notes above on toxicity.
A tea made from the bark is purgative[
The leaves are stimulant[
The medicinal properties of this species are similar to those of Rhododendron anthopogon[
]. These are:-
A decoction of the leaves is used in the treatment of colds, coughs, chronic bronchitis, asthma and excessive mucus
formation in the nose or throat[
The leaves and flowers are used in treating indigestion and lung infection in Pso-ring-pa (an indigenous system of medicine among Tibetans)[
The aromatic leaves are used as a snuff to produce sneezing[
The dried and powdered flowers, mixed with oil, are used as massage oil for the body in the treatment of post-delivery complications[
Seed - best sown in a greenhouse as soon as it is ripe in the autumn and given artificial light. Alternatively sow the seed in a lightly shaded part of the warm greenhouse in late winter or in a cold greenhouse in mid spring. Surface-sow the seed and do not allow the compost to become dry[
]. Pot up the seedlings when they are large enough to handle and grow on in a greenhouse for at least the first winter.
Layering in late July. Takes 15 - 24 months[
Cuttings of half-ripe wood, August in a frame. Easy[