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Ericaceae FAMILY

Rhododendron tomentosum

Rhododendron tomentosum

Edibility
2/5
Medicinal
3/5

Safety & Hazards

Plants contain a narcotic toxin called Ledol - this is a sesquiterpene that can cause cramps, paralysis, and delirium. Ledol is also said to have various beneficial effects if consumed in the correct dosage and it is said that, when ingested as a herbal tea, it only causes problems if the leaves are cooked for a long period in a closed container[1].

Cultivation Details

HabitEvergreen Shrub
Growth—

Rhododendron tomentosum is a moderately cold-hardy plant, able to tolerate temperatures down to around -15°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[2]. Requires a lime-free loam or peaty soil[3, 4]. Prefers a moist humus-rich acid soil in shade or semi-shade[2]. Plants flower more freely when grown in a sunny position. Plants grow better if they have certain fungal associations in the soil. The best way of providing this is to incorporate some soil from around well-growing established plants into the soil for the new plant[2]. Hardy to at least -15°c[2]. The leaves are very aromatic[5]. When crushed, they smell strongly of hops[6]. Plants benefit from removing the dead flowers before they set seed[7]. This prevents them putting too much energy into seed production at the expense of more flowers and leaves. The flowers contain an oil that smells strongly of antiseptic[6].

Propagation

Seed - surface sow in a shady part of the greenhouse in late winter or early spring[8, 9]. Another report says that the seed is best sown in the autumn as soon as it is ripe[7]. Germination is variable and can be quite slow. Prick out the seedlings into individual pots as soon as they are large enough to handle and grow the pots on in a shady frame for 18 months before planting them out into their permanent positions[8]. Cuttings of half-ripe wood, 5 - 8cm with a heel, mid summer in a frame. Plant out in spring. Fair percentage[8]. Cuttings of mature wood, late autumn in a frame[9]. Layering in the autumn. Takes 12 months[8]. Division. Cite as: Temperate Plants Database, Ken Fern. temperate.theferns.info. 2026-02-21. <temperate.theferns.info/plant/Rhododendron+tomentosum>

Pollinators

Bees

References

  1. [1]Discovering Wild Plants - Alaska, W. Canada and the Northwest. — Schofield. J. J. · Alaska Northwest Books; Alaska · 2003 · ISBN 0882403699 ↩︎A nice guide to some useful plants in that area.
  2. [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. [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. [4]Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement. — Bean. W. · Murray · 1981 · ISBN - ↩︎A classic with a wealth of information on the plants, but poor on pictures.
  5. [5]Ornamental Shrubs, Climbers and Bamboos. — Thomas. G. S. · Murray · 1992 · ISBN 0-7195-5043-2 ↩︎Contains a wide range of plants with a brief description, mainly of their ornamental value but also usually of cultivation details and varieties.
  6. [6]The Complete Homeopathy Handbook. — Castro. M. · Macmillan. London. · 1990 · ISBN 0-333-55581-3 ↩︎A concise beginner's guide to the subject. Very readable.
  7. [7]The RHS Gardener's Encyclopedia of Plants and Flowers — Brickell. C. · Dorling Kindersley Publishers Ltd. · 1990 · ISBN 0-86318-386-7 ↩︎Excellent range of photographs, some cultivation details but very little information on plant uses.
  8. [8]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.
  9. [9]The Reference Manual of Woody Plant Propagation. — Dirr. M. A. and Heuser. M. W. · Athens Ga. Varsity Press · 1987 · ISBN 0942375009 ↩︎A very detailed book on propagating trees. Not for the casual reader.
  10. [10]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.
  11. [11]Cornucopia - A Source Book of Edible Plants. — Facciola. S. · Kampong Publications · 1990 · ISBN 0-9628087-0-9 ↩︎Excellent. Contains a very wide range of conventional and unconventional food plants (including tropical) and where they can be obtained (mainly N. American nurseries but also research institutes and a lot of other nurseries from around the world.
  12. [12]A Modern Herbal. — Grieve. · Penguin · 1984 · ISBN 0-14-046-440-9 ↩︎Not so modern (1930's?) but lots of information, mainly temperate plants.
  13. [13]A Field Guide to Medicinal Plants. Eastern and Central N. America. — Foster. S. & Duke. J. A. · Houghton Mifflin Co. · 1990 · ISBN 0395467225 ↩︎A concise book dealing with almost 500 species. A line drawing of each plant is included plus colour photographs of about 100 species. Very good as a field guide, it only gives brief details about the plants medicinal properties.
  14. [14]Native American Ethnobotany — Moerman. D. · Timber Press. Oregon. · 1998 · ISBN 0-88192-453-9 ↩︎Very comprehensive but terse guide to the native uses of plants. Excellent bibliography, fully referenced to each plant, giving a pathway to further information. Not for the casual reader.
  15. [15]Edible and Medicinal Plants. — Launert. E. · Hamlyn · 1981 · ISBN 0-600-37216-2 ↩︎Covers plants in Europe. a drawing of each plant, quite a bit of interesting information.