Rhus radicans L.

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Article from Bean's Trees and Shrubs Hardy in the British Isles

Recommended citation
'Rhus radicans' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhus/rhus-radicans/). Accessed 2022-05-24.


Common Names

  • Poison Ivy


  • R. toxicodendron of many authors, in large patt, not L.
  • Toxicodendron radicans (L.) Kuntze


A fleshy dehiscent or indehiscent fruit with one to several seeds each enclosed in a hard endocarp (the stone).
With an unbroken margin.
Lacking hairs smooth. glabrescent Becoming hairless.
Leaf-like segment of a compound leaf.
Egg-shaped; broadest towards the stem.
Small grains that contain the male reproductive cells. Produced in the anther.
Having only male or female organs in a flower.


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Article from Bean's Trees and Shrubs Hardy in the British Isles

Recommended citation
'Rhus radicans' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/rhus/rhus-radicans/). Accessed 2022-05-24.

A deciduous shrub, either climbing or loosely spreading in habit, the climbing form attaching itself to rocks, walls, trunks of trees, etc., by means of aerial roots like those of the ivy, and frequently reaching to a considerable height; the bushy form up to 8 or 9 ft high. Leaves always composed of three leaflets, the side ones very shortly stalked, the end one with a stalk 12 to 114 in. long, the common leaf-stalk 2 to 4 in. long. Leaflets very variable in size, shape, and toothing, broadly ovate to obovate, pointed, sometimes quite entire, often coarsely and irregularly notched at the margin, and either glabrous or slighdy downy beneath. The terminal leaflet is always the largest, and from 2 to 5 in. long, the lateral ones about two-thirds as large. Flowers dull white, 16 in. across, on slender panicles 112 to 212 in. long, often unisexual, the sexes sometimes separated. Fruit a round, whitish drupe, 14 in. wide, smooth or downy. Bot. Mag. t. 1806.

The poison ivy is very abundant in N. America and Mexico. As a garden plant its chief value is in the beautiful red tints of its autumn foliage. It was cultivated by Compton, Bishop of London, at Fulham, in the 17th century. The poisonous effects of the sap – a yellowish milk-like fluid which soon turns black on exposure – have long been known. As long ago as 1623, the author of the Historye of the Bermudaes referred to them. On the skin of many persons, but far from all, the sap produces blisters and eczema-like eruptions, which are exceedingly painful and persistent. The supposed active principle, ‘toxicodendrol’, is insoluble in water, and it is of no use to attempt to remove it from the skin by ordinary washing. The best-known remedy to apply is an alcoholic solution of sugar of lead (lead acetate), and the sooner it is used on the affected parts the more effective it is. So serious are the effects of the rhus poison on some people that the plant should never be grown where anyone unaware of its dangerous properties could come in contact with it. Even in England I know of a man who had been making cuttings of it for propagation, who was kept in hospital for several months through the almost corrosive effects of the sap. It is said that the symptoms are sometimes recurrent, and that on some persons the eruptions break out annually at the same time of year, but with decreasing virulency. This phenomenon, extraordinary if true, does not appear to have been conclusively established, although the testimony of patients is on record who aver that they have had second and third attacks, although they have never been near the plant after the first. In my experience mere contiguity to the plant without touching it will not induce skin poisoning, although when in flower the escaping pollen appears to have evil effects, especially on the eyes, in N. America.

There is one other property of this remarkable plant to which attention may be drawn. This is the indelibility of its juice when applied to linen. It produces a quite ineradicable stain, and is, in fact, one of the best possible marking inks available.

R diversiloba Torr. & Gr

Usually a shrub. Leaflets rounded to obtuse at the apex, or abruptly narrowed to an acute point, the terminal one lobed or sinuate. Western N. America. It is just as poisonous as R. radicans.

R orientale (Greene) Schneid.

Toxicodendron orientale Greene
T. radicans subsp. orientale (Greene) Gillis
R. ambigua of some authors, not (?) Lav. ex Dipp.
Ampelopsis japonica Hort., in part

A native of Japan, Sakhalin, the Kuriles, China, and Formosa, very closely allied to R. radicans, differing in its hispid fruits. This rhus, which is just as poisonous as its American relative, was once grown in nurseries and gardens under the wrong and misleading names “Ampelopsis hoggii” and “A.japonica”, which are properly synonyms of the Japanese creeper Parthenocissus tricuspidata.

Rtoxicodendron L Poison Oak

A sparsely branched shrub spreading by suckers. Petioles and undersides of leaflets velvety-pubescent; leaflets elliptic or rhombic-ovate, variously lobed. Native of the south-eastern USA in the coastal plain. The name R. toxicodendron has been wrongly applied to R. radicans.

var. rydbergii (Small) Rehd.

R. rydbergii Small

A small, non-climbing, sparsely branched shrub, spreading by underground runners. Leaves clustered at the ends of the shoots, glabrous except for the usually downy veins beneath; terminal leaflet broad-ovate to almost orbicular, abruptly acuminate. Native mainly of the western USA and British Columbia, but also reported from the east.