Rhododendron blinii H.Lév.
Rhododendron costulatum Franch.
Rhododendron lemeei H.Lév.
Rhododendron lutescens is an evergreen shrub of loose habit that usually grows 1 - 2 metres tall but can reach 3 metres[
The plant is often grown as an ornamental, where it can be used to form a hedge.
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 - southern China (Sichuan)
Hillsides, scrub, hedges and forest edges usually fully exposed to the sun; at elevations from 1,750 - 3,000 metres[
]. Wet areas in mixed forests, thickets on limestone slopes[
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Rhododendron lutescens is a somewhat cold-hardy plant, able to tolerate temperatures down to around -8 to -15°c when fully dormant[
]. This is one of the earliest Rhododendron species to come into flower and new growth in the Spring. Although cold-tolerant when dormant, the flowers and young growth are very susceptible to damage by any frosts that occur at this time[
Succeeds in a most humus-rich lime-free soils except those of a dry arid nature or those that are heavy or clayey[
]. Prefers a peaty or well-drained sandy loam[
]. Succeeds in sun or shade, the warmer the climate the more shade a plant requires[
]. A pH between 4.5 and 5.5 is ideal[
], though this species has been shown to tolerate a neutral to slightly alkaline soil[
]. Somewhat heat and drought tolerant.
Succeeds in a woodland though, because of its surface-rooting habit[
], it does not compete well with surface-rooting trees[
]. Plants need to be kept well weeded, they dislike other plants growing over or into their root system, in particular they grow badly with ground cover plants, herbaceous plants and heathers[
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[
A very ornamental plant[
Plants in this genus are notably susceptible to honey fungus[
Plants are being grown as a medium-sized hedge at Wisley, RHS gardens in Surrey[
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. Difficult[