Common Name: Alpenrose

General Information

Rhododendron ferrugineum is a dwarf, evergreen shrub of close habit - it can eventually reach up to 1.50 metres tall and wide, forming a dense hemispherical mass[].
The plant is harvested from the wild for local use as a medicine and source of materials.. It is sometimes grown as an ornamental in gardens, where it can be used to form a ground cover.
Rhododendron ferrugineum is an abundant species in montane areas of the Alps and Pyrenees. It has a relatively wide distribution, stable populations and no major threats. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known 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[].

Botanical References

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Range

Europe - mountainous regions from Spain to Germany and east to Austria and the Balkans.

Habitat

Acidic soils associated with Pinus species[]. Mountain slopes in open woods or scrub, often dominant in the dwarf shrub zone; at elevations from 1,600 - 2,200 metres[, ].

Properties

Conservation Status	Least Concern
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	1.50 m
Growth Rate	Slow
Pollinators	Insects, Self
Self-fertile	Yes
Cultivation Status	Ornamental, Wild

Cultivation Details

Rhododendron ferrugineum is a very cold-tolerant plant, when fully dormant it can withstand temperatures down to about -30°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[]. It grows best in areas with cold winters and summers that are not hot and dry[].
Succeeds in 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[].
A slow-growing plant, though it can be long-lived with a plant 300 years or more old being recorded[, ].
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[].
Plants in this genus are notably susceptible to honey fungus[].

Edible Uses

None known

Medicinal

Some caution is advised in the medicinal usage of this plant - see the notes above on toxicity.

The flowers, leaves and the galls are antirheumatic, diaphoretic and diuretic[, , ]. It is used in the treatment of certain forms of arthritis and rheumatism, but can cause diarrhoea and vomiting so should only be used with expert supervision[].

A homeopathic remedy is made from the plant[]. It is used in treating a variety of complaints involving flatulence[].

Agroforestry Uses:

Plants can be grown as ground cover when spaced about 1 metre apart each way[].

Other Uses

Some substances in this plant have shown herbicidal activity, though more research needs to be carried out[].

An extract of a culture of the leaf cells is used as an ingredient in commercial cosmetic preparations as a skin conditioner[].
An extract of the flowers is used as an ingredient in commercial cosmetic preparations as a skin conditioner[].
An extract of the plant (part not specified) is used as an ingredient in commercial cosmetic preparations as a masking agent and skin protector[].

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[]. 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[].