Common Name: Wild Rosemary

General Information

Rhododendron tomentosum is an evergreen shrub with creeping or prostrate stems growing from a rhizomatous rootstock; it can grow up to 100cm tall[].
The plant is harvested from the wild for local use as a food, medicine and source of materials. It is grown as an ornamental in gardens.

Known 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[].

Botanical References

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Range

Northern Eurasia - Norway to Germany, through Russia to Russian Far Easr, Japan N.Korea; Northern N. America - Alaska & BC to Greenland & Newfoundland

Habitat

Bogs, muskeg, tundra, raised beach ridges; at elevations up to 1,800 metres[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	0.50 m
Pollinators	Bees
Cultivation Status	Ornamental, Wild

Cultivation Details

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[].
Requires a lime-free loam or peaty soil[, ]. Prefers a moist humus-rich acid soil in shade or semi-shade[]. 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[].
Hardy to at least -15°c[].
The leaves are very aromatic[]. When crushed, they smell strongly of hops[].
Plants benefit from removing the dead flowers before they set seed[]. 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[].

Edible Uses

A tea is made from the aromatic leaves[, ]. Considered by some to be a better tea than that made from L. groenlandicum[]. Some caution is advised, see the notes above on toxicity. It would be better to brew the tea in cold water by leaving it in a sunny place, or to make sure that it is brewed for a short time only in an open container.

The leaves are used as a flavouring, they are a bayleaf substitute[].
The plant has been used as a hop substitute in making beer, though this has caused an unpleasant kind of drunkenness which is accompanied by a headache and dizziness[].

Medicinal

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

The leaves and young flowering shoots are astringent, diaphoretic, disinfectant, diuretic, laxative, pectoral, stomachic and tonic[, , , ]. A tea is taken internally in the treatment of asthma, coughs, colds, stomach aches, kidney ailments etc[, , ].
Externally, it is used as a wash for burns, ulcers, stings, infections etc[, ].
Some caution should be exercised. The plant is more strongly narcotic than Rhododendron groenlandicum[] and should not be used without expert supervision[].

A homeopathic remedy is made from the whole, dried and powdered, plant[]. This is used in the treatment of stings, injuries and joint pains[]. It is also used in the treatment of various chest complaint, asthma, menstrual pain etc[].

Agroforestry Uses:

A good bee plant[].

Other Uses

The leaves are hung up in the clothes cupboard in order to repel insects[, ]. The branches are also placed among grain in order to keep mice away[, ].
A strong decoction of the leaves is used to kill lice and insects[, ].

The leaves contain tannin[].

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.