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Common Name: Sheep Laurel

General Information

Kalmia angustifolia is an evergreen shrub that can grow up to 1.50 metres tall.
It is harvested from the wild for local use as a medicine..

Known Hazards

The foliage is poisonous to animals[, , ]. The whole plant is highly toxic[].
All parts of the plant (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 oder to favour the bumblebee and improve fertilization rates[].

Botanical References

, ,

Range

Eastern N. America - Newfoundland to Hudson Bay, south to Georgia and Michigan. Nat in Britain.

Habitat

Acidic bogs and swamps[].

Properties

Medicinal Rating
Habit	Evergreen Shrub
Height	1.50 m
Pollinators	Bees
Cultivation Status	Wild

Cultivation Details

Requires an acid humus-rich soil, succeeding in part shade[] or in full sun in cooler areas. Prefers almost full sun[]. Dislikes dry soils[], requiring cool, permanently moist conditions at the roots[]. Succeeds in open woodland or along the woodland edge[].
Plants are very cold-hardy, tolerating temperatures down to about -30°c[].
A very ornamental and variable plant[], there are many named varieties[]. The flowers are produced at the end of the previous years growth[]. Plants spread slowly by means of suckers[].
Pruning is not normally necessary, though if older plants become bare at the centre they can be cut back hard and will regrow from the base[].

Edible Uses

None known

Medicinal

Sheep laurel is a very poisonous narcotic plant the leaves of which were at one time used by some native North American Indian tribes in order to commit suicide[]. It is little, if at all, used in modern herbalism.
The leaves are usually used externally as a poultice and wash in herbal medicine and are a good remedy for many skin diseases, sprains and inflammation[, ]. They can also be applied as a poultice to the head to treat headaches[]. The singed, crushed leaves can be used as a snuff in the treatment of colds[].
Used internally, the leaves are analgesic, astringent and sedative and have a splendid effect in the treatment of active haemorrhages, headaches, diarrhoea and flux[, , , ]. This species is said to be the best for medicinal use in the genus[]. The plant should be used with great caution however, see the notes above on toxicity.

Other Uses

None known

Propagation

Seed - surface sow in late winter in a cool greenhouse in light shade[, ]. Prick out the young seedlings into individual pots as soon as they are large enough to handle. The seedlings are rather sensitive to damping off, so water them with care, keep them well-ventilated and perhaps apply a fungicide such as garlic as a preventative. Grow the young plants on in light shade and overwinter them in the greenhouse for their first winter[]. Plant them out into their permanent positions in early summer. The seed is dust-like and remains viable for many years[].
Cuttings of half-ripe wood, August in a frame. Very poor results unless the cuttings are taken from very young plants[, ].
Layering in mid summer to early autumn. Takes 18 months[]. The plants can also be dug up and replanted about 30cm deeper in the soil to cover up some of the branches. The plant can then be dug up about 12 months later when the branches will have formed roots and can be separated to make new plants[].