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Common Name: Swamp Laurel
Kalmia polifolia is an evergreen shrub that can grow up to 0.50 metres tall.
It is harvested from the wild for local use as a medicine..
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[
Northern N. America - Newfoundland to Hudson Bay, southwards. Nat. in Britain in a bog in Surrey.
Cold peat bogs and other wet places[
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[
A very cold-hardy plant, tolerating temperatures down to about -30°c[
A very ornamental plant[
], there are some named varieties[
Pruning is not normally necessary[
Swamp 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, it at all, used in modern herbalism though the leaves are a good external treatment for many skin diseases and inflammation[
The leaves are astringent and sedative[
]. They are used externally to make a poultice or a wash in the treatment of many skin diseases, open sores, wounds that will not heal and inflammation[
Used internally, the leaves have a splendid effect in the treatment of active haemorrhages, diarrhoea and flux[
]. They should be used with great caution however, and only under the supervision of a qualified practitioner. See the notes above on toxicity.
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[