Common Name: Hairy Alpenrose

General Information

Rhododendron hirsutum is a dwarf, evergreen shrub of close habit - it can eventually reach up to 100cm tall and wide, forming a dense hemispherical mass[].
The plant is harvested from the wild for local use as a medicine. It is grown as an ornamental in gardens, being valued as one of the few speecies in this genus that can succeed in a calcareous soil[].
Rhododendron hirsutum is an abundant species in montane areas of the Alps; it has a relatively broad distribution, stable populations and no major threats. It has, however, declined in Croatia where it was collected from the wild for medicinal value, but it is now a protected species there. Globally, 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

Range

Europe - mountainous areas from France to Germany, south to Italy and Croatia

Habitat

Dry, open, stony soils and screes, growing in dwarf shrub heath and herb rich grassland above the tree line, preferring calcareous soils; at elevations up to 2,500 metres[, ].

Properties

Conservation Status	Least Concern
Medicinal Rating
Habit	Evergreen Shrub
Height	1.00 m
Growth Rate	Slow
Cultivation Status	Ornamental, Wild

Cultivation Details

Rhododendron hirsutum 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[].
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[].

Edible Uses

None known

Medicinal

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

Used as a medicinal and aromatic plant for the treatment of inflammation, pain, skin ailments, common cold and gastro-intestinal disorders[].

Other Uses

None known

Propagation

Seed - surface sow in a shady part of the greenhouse in late winter or early spring[, ]. Another report says that the seed is best sown in the autumn as soon as it is ripe[]. 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[].
Cuttings of half-ripe wood, 5 - 8cm with a heel, mid summer in a frame. Plant out in spring. Fair percentage[].
Cuttings of mature wood, late autumn in a frame[].
Layering in the autumn. Takes 12 months[].
Division.