Azalea setosa (D.Don) Kuntze
Rhododendron setosum is a low-growing, evergreen shrub of close, bushy habit; it usually grows from 10 - 30cm tall, occasionally reaching 120cm[
The plant is harvested from the wild for local use as a tea[
]. It is sometimes 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 (Xizang), Nepal, Bhutan, India (West Bengal, Sikkim)
Rhododendron thickets, open scrub, alpine meadows; at elevations from 3,500 - 4,800 metres[
]. Mountain forests; at elevations from 3,700 - 5,600 metres in Nepal[
|Cultivation Status||Ornamental, Wild
Rhododendron setosum is native to higher elevations in the Himalayasf, where it can be found at elevations up to 4,800 metres. A moderately cold-tolerant plant, when fully dormant it can withstand temperatures down to about -20°c. 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[
]. The plant grows best in regions where there is a covering of snow in the winter and a clear movement in the seasons from winter into 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[
The plant emits a strongly resionous odour[
]. 'The species certainly abounds near the summits of all the passes, and after hot sunshine fills the atmosphere with its powerful aroma, far too heavy to be agreeable, and greatly aggravating the discomforts of toiling in the rarefied medium of these elevations' (Hooker)[
Some caution is advised if consuming this plant - see the notes above on toxicity.
The dried petals are used as a tea substitute[
The plant is used medicinally, usually in the form of a herbal tea. It is believed to be antiseptic and to improve the efficacy of the immune system, and is also used to treat diarrhoea and fevers[
The dried petals are the part of the plant most commonly used, though the stems and other parts are also sometimes used[
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[