Toxicodendron radicans is very variable and several different subspecies and varieties are recognised. Most of these are native to N. America, the subspecies hispidum is the only form native to China[
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.
Philostemon radicans (L.) Raf.
Rhus eximia (Greene) Standl.
Rhus intermedia Hayata
Rhus radicans L.
Rhus rydbergii Small ex Rydb.
Rhus toxicodendron hispida Engl.
Rhus toxicodendron pubens Engelm. ex S.Watson
Rhus toxicodendron radicans (L.) Torr.
Rhus toxicodendron rydbergii (Small ex Rydb.) Garrett
Rhus verrucosa Scheele
Toxicodendron negundo Greene
Toxicodendron radicans eximium (Greene) F.A.Barkley
Toxicodendron vulgare Mill.
Common Name: Poison Ivy
Toxicodendron radicans is a multi-stemmed, deciduous shrub, often adopting a climbing habit. As a shrub, the stems can be erect or decumbent and up to 2 metres tall. When climbing, the stems will usually attach themselves to supports by means of adventitious roots and this can allow stems to become much longer, with reports of up to 45 metres.
The plant is harvested from the wild for local use as a medicine and source of materials.
This plant contains toxic substances and skin contact with it can cause severe irritation to some people, though most wildlifr and livestock are not affected by it[
]. The sap is extremely poisonous[
]. The sap contains 3-N pentadecycatechnol. Many people are exceedingly sensitive to this, it causes a severe spreading dermatitis. The toxins only reach the skin if the plant tissues have been damaged, but even indirect contact can cause severe problems[
Eastern N. America - Ontario to Quebec, south to Texas and Florida; E. Asia - China (Guizhou, Hubei, Hunan, Sichuan, Taiwan, Yunnan)
Woods, on rocky slopes and in wooded swamps[
]. Hill forests; at elevations from 600 - 2,200 metres in southern China (var hspida)[
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Toxicodendron radicans is a very cold-hardy plant, able to tolerate temperatures down to around -25°c when fully dormant[
]. It is often found in continental climates with short, warm to hot summers and long, cold to cool winters[
]. The young growth in spring is cold-sensitive and can be damaged by late frosts. Mean annual precipitation can range from 390 - 1,450mm, and it experiences between 300 - 1,880mm of snowfall over most of its range[
Species in this genus generally succeed in a well-drained fertile or moderately fertile soil in full sun or light shade[
]. This species is able to tolerate a wide range of conditions in the wild, including dry soils, poorly-drained clays with gleying, well-drained silts and loamy sands[
]. Plants are often found in acid soils, where the pH can be as low as 3.6, they also succeed in moderately alkaline soils with a pH around 8[
A fast-growing but short-lived species in the wild[
Plants take 3 years from seed to reach the flowering stage[
The plant has 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 dioecious species - both male and female forms must be grown if fruit and seed are required.
Poison ivy has occasionally been used medicinally, though it is an extremely poisonous plant and great caution should be exercised. Any herbal use should only be undertaken under the supervision of a qualified practitioner. See also the notes above on toxicity.
This plant has been used in the past by physicians in the treatment of paralysis and liver disorders[
A decoction of the leaves has been used as a tonic and rejuvenator[
]. The whole or the broken leaves have been rubbed over the skin to treat boils and skin eruptions[
The leaves have been rubbed on skin that has been affected by a poison ivy reaction[
Because of its extensive root system with abundant rhizomes that can create dense thickets of growth, poison-ivies may be useful for the revegetation of disturbed areas. However, there are many non-poisonous species that can provide equal or better rehabilitation value than poison-ivies, with the added advantage of being non-toxic to humans[
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[
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, oblique-ovoid drupe is around 5mm × 6mm with a thick, waxy mesocarp[
An excellent marking ink is obtained from this plant[
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[