Rhododendron periclymenoides
Rhododendron periclymenoides
Safety & Hazards
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[1].
Cultivation Details
Rhododendron periclymenoides is a very cold-tolerant plant, when fully dormant it can withstand temperatures down to about -35°c[2]. 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[2]. 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[3, 2]. This species will also grow well in dense woodland shade[4]. Most species strongly dislike soils of a dry arid nature, heavy soils or clays, though this species is known to succeed in dryish sandy or rocky soils[3, 5]. Prefers a peaty or well-drained sandy loam[3]. Succeeds in sun or shade, the warmer the climate the more shade a plant requires[2]. Requires a pH between 4.5 and 5.5[2]. 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[2, 5]. 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[2]. The plant can regenerate by resprouting from the root crown if it is cut back severely[4]. The flowers are slightly fragrant[6].
Propagation
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[2]. 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[7]. Cuttings of half-ripe wood, August in a frame[7]. Cite as: Temperate Plants Database, Ken Fern. temperate.theferns.info. 2026-02-21. <temperate.theferns.info/plant/Rhododendron+periclymenoides>
Pollinators
Data unavailable
References
- [1]Grayanotoxin Poisoning: ‘Mad Honey Disease’ and Beyond — Jansen S.A. et al · 2012 · https://doi.org/10.1007/s12012-012-9162-2 ↩︎An in-depth review of the literature on the toxic effects of a toxin widely found in the family Ericaceae
- [2]The New RHS Dictionary of Gardening. 1992. — Huxley. A. · MacMillan Press · 1992 · ISBN 0-333-47494-5 ↩︎Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
- [3]RHS Dictionary of Plants plus Supplement. 1956 — F. Chittendon. · Oxford University Press · 1951 · ISBN - ↩︎Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaced in 1992 by a new dictionary (see [ 200 ]).
- [4]Fire Effects Information System — http://www.feis-crs.org/feis/ ↩︎An on-line information site with comprehensive information on over 1,100 species of plant. Mainly developed to supply information on the effects of fire on plants and animals, it also contains a wealth of other information on the plants
- [5]KemperCentreForHomeGardeningPlantFinder — Missouri Botanical Garden · http://www.mobot.org/gardeninghelp/plantfinder/ ↩︎Basic cultivation details, plant uses, habitat etc for several thousand species of plants, mainly from the temperate zone.
- [6]Flora of N. America — http://flora.huh.harvard.edu/fna/ ↩︎An on-line version of the flora with an excellent description of the plant including a brief mention of plant uses.
- [7]Propagation of Trees, Shrubs and Conifers. — Sheat. W. G. · MacMillan and Co · 1948 · ISBN - ↩︎A bit dated but a good book on propagation techniques with specific details for a wide range of plants.
- [8]Food Plants in the Americas: A Survey of the Domesticated, Cultivated, and Wild Plants Used for Human Food in North, — Kermath B.M.; Bennett B.C.' Pulsipher L.M. · 2014 ↩︎A pre-publication draft of an amazing, on-going work first started in 1985. It contains information on more than 3,900 taxa from the Americas - from Arctic regions to the Tropics
- [9]A Dictionary of Plants Used by Man. — Usher. G. · Constable · 1974 · ISBN 0094579202 ↩︎Forget the sexist title, this is one of the best books on the subject. Lists a very extensive range of useful plants from around the world with very brief details of the uses. Not for the casual reader.