There has been considerable uncertainty amongst botanists as to the best way of treating the genus Toxicodendron, with some viewing it as a genus distinct from Rhus, whilst others see insufficient differences and lump the two genera under Rhus. Toxicodendron is treated here as distinct, with two of the major differences from a gardener’s viewpoint being that Toxicodendron has a toxic sap (not toxic in Rhus) and the fruits have a thick, waxy mesocarp.
Rhus echinocarpa H.Lév.
Rhus trichocarpa Miq.
Toxicodendron trichocarpum is a deciduous shrub or a tree usually growing up to 6 metres tall.
The plant is harvested from the wild for local use as a source of materials.
Species in the genus Toxicodendron are known to contain resinous phenolic compounds known as urushiols that can cause severe skin problems in humans. Direct contacr with the plant, exposure to smoke or fumes from a burning plant or even contact with pets, animals or cothing that have touched the plant can cause severe allergic dermatitis in some individuals. There is usually a latent period of about 12 - 24 hours from the moment of contact, this is followed by a reddening and severe blistering of the skin. Even plant specimens 100 or more years old have been known to cause problems[
The plant does not cause skin problems with wildlife or livestock - the foliage and fruits are eaten by several other species of animals and birds - though some pets are sensitive to it[
E. Asia - southern China (Anhui, Fujian, Guizhou, Hubei, Hunan, Jiangxi, Zhejiang), Japan, Korea.
Hills and mountains all over Japan[
]. Hill and mountain forests, thickets; at elevations from 900 - 2,000 metres[
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Toxicodendron trichocarpum is only hardy outdoors in the milder regions of the temperate zone. The young growth in spring is more susceptible to cold and can be damaged by late frosts.
Species in this genus generally succeed in a well-drained fertile or moderately fertile soil in full sun or light shade[
Plants have brittle branches and these can be broken off in strong winds[
]. Plants are also susceptible to coral spot fungus[
]. Plants in this genus are notably resistant to honey fungus[
A very ornamental plant[
]. The bruised leaves have a resinous aroma[
A dioecious species - both male and female forms must be grown if fruit and seed are required[
]. Another report says that this species is possibly apomictic (it produces fertile seed without fertilization, each seedling being a clone of the parent plant)[
An oil is extracted from the seeds[
]. It attains a tallow-like consistency on standing and is used to make candles. These burn brilliantly, though they emit a pungent smoke[
]. The yellow, oblate drupe is 5 - 6mm x 7 - 8mm with a thick, waxy mesocarp[
The leaves are rich in tannin. They can be collected as they fall in the autumn and used as a brown dye or as a mordant[
Seed - best sown in a cold frame as soon as it is ripe. Pre-soak the seed for 24 hours in hot water (starting at a temperature of 80 - 90c and allowing it to cool) prior to sowing in order to leach out any germination inhibitors[
]. The stored seed also needs hot water treatment and can be sown in early spring in a cold frame[
]. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts.
Cuttings of half-ripe wood, 10cm with a heel, mid summer in a frame[
Root cuttings 4cm long taken in December and potted up vertically in a greenhouse. Good percentage[
Suckers in late autumn to winter[