Common Names

Poison-ivy is also recognized under the names poison-oak, poison-vine and three-leaved ivy.

Plate. XXIV

Poison Ivy.

Photo - F. Fyles.

Poison Ivy.


Poison-ivy is a low shrub which is propagated by under-ground branches as well as by seeds. It scrambles over stumps of trees or, as in the case of the variety radicans, it climbs by means of serial rootlets to some height up fence posts and the trunks of trees. The long stalked leaves are divided into three distinct leaflets, which are mostly ovate, pointed, entire or with a few irregular coarse teeth, bright green above, paler and slightly hairy beneath, changing to rich autumnal colours. The flowers are small, inconspicuous, greenish or whitish, loosely clustered in the axils of the leaves. As the flower cluster is surpassed by the long-stalked leaves it is seldom seen unless the foliage is moved aside. The berries are greenish-white or cream coloured, slightly shining, round, smooth, with longitudinal ridges at intervals. The flowers are in bloom from April till June.


It is a native of Canada and is commonly found in hedgerows, thickets and dry woods from Nova Scotia to British Columbia, where it passes into a thicker-leaved and smoother form (R. Rydbergii Small).

Poisonous Properties

Poison ivy is the worst vegetable skin poison in America, hundreds of people being poisoned each year. The poisonous constituents have not yet been satisfactorily determined. Cases of poisoning are often reported where the individual has passed the plant without coming in contact with it. This has been explained by the fact that pollen grains, minute hairs and even exhalations from the plant are sufficient to cause eruptions on the skin of a susceptible person. The poison may even be carried on the clothing or tools of someone who has been in contact with it, or it may be that, as the effect of the poison does not appear for some time, the occasion of coming in contact with it may have been quite forgotten. On the other hand, many people handle it frequently with no ill effect.

Cattle can eat it with impunity, but dogs are poisoned by it.


Inflammation of the skin begins to appear from eighteen hours to several days after contamination, and is characterized by intense irritation and burning, swelling and redness, followed by blisters and pain. Symptoms of internal poisoning are burning thirst, nausea, faintness, delirium, and convulsions.

Remedy And Means Of Control

Many remedies have been suggested to allay this burning and irritation, one of the simplest being the immediate washing of the parts affected with good strong yellow laundry soap. On return from a day's outing where there was danger of meeting with poison-ivy, the liberal use of such a soap might prevent much suffering, a piece might even be carried in the pocket.

An application of absorbent cotton saturated with a solution of common baking soda is simple and efficacious. In the case of severe poisoning the aid of a physician should be obtained.

To properly eradicate this pest the underground root stocks must be destroyed as well as the flowering tops. Grubbing out and burning it by some one who is immune to the poison is the surest means. Spraying with hot brine, or caustic soda will kill it. One pound of caustic soda to two gallons of water has been found most effective.