POISON IVY
Scientific Name: Rhus radicans L.
Other Names: herbe à la puce, sumac vénéneux, sumac grimpant, bois de chien; incorrectly called Poison-oak which is Rhus toxicodendron L. and does not occur in eastern Canada
Family: Cashew Family (Anacardiaceae)
General Description: Perennial, spreading by seed and by woody rhizomes (underground stems) which produce dense patches.
Habitat: Poison ivy occurs under forests, in edges of woodland, meadows, waste areas, fence lines, and roadsides throughout most of Ontario south of a line from North Bay to Kenora. The tall climbing vine form, however, is mainly confined to the counties bordering Lake Erie, Lake Ontario and the lower Ottawa Valley.
Stems
- Woody and of two kinds:
- Horizontally growing stem (most frequent):
- Grows on or just below the ground surface
- Has upright leafy stalks 10-80 cm (4-32 in.) high
- Climbing vine:
- Develops aerial roots
- May climb 6-10 m per node,
Leaves
- Compound, each compound leaf consisting of 3 leaflets at the tip of a long leafstalk (petiole)
- Middle leaflet has a longer stalk than the 2 side leaflets
- Overall leaflet shape and type of toothing highly variable between leaflets on the same stem, as well as among plants within a patch and between patches
- Leaflets ranging from narrow to broadly ovate with a smooth margin, to a few scattered, shallow, rounded teeth, to several, coarse, deep-pointed teeth which give the leaflet a lobed appearance
- Purplish to reddish when unfolding in spring (May to early June)
- Bright green and often shiny (with a varnished appearance) in summer
- Vivid orange-red to wine-red in autumn in sunny areas, but often lacking the bright colour in shaded places
- Leaflet smooth and hairless on both surfaces except for small tufts of brownish hair on the underside along the mid-vein and in the angles formed by the mid-vein and some of the lower branching veins
Flowers
- Small
- White or greenish
- 5 sepals
- 5 petals
- In branching clusters from the leaf axils (angles between leafstalk and stem)
- Flower clusters inconspicuous because they are often hidden below the dense leaf canopy and because many plants do not flower every year
- Flowers in June and July
Fruit
- Dry, berry-like fruit
- Whitish to dull greenish-yellow
- About 5 mm (1/5 in.) in diameter
- With lengthwise ridges somewhat resembling a peeled orange
- Produced by September but often remaining on the low leafless stems all winter
Often Confused With
Poison-oak- Poison ivy is distinguished by its low growth or its occasional climbing habit, its 3 leaflets in each compound leaf, its leaves deep green in summer, reddish in spring and fall, its clusters of whitish to greenish-yellow berries, and its short, erect, leafless stems which frequently retain a few berries all winter long. The true Poison-oak occurs in the southern United States, but not in Canada.
Caution: All parts of poison-ivy, including the roots, contain a poisonous substance which causes an irritating inflammation of the skin of most people, the inflamed areas frequently developing blisters and accompanied by intense itchiness. The poisonous substance is an oily resin contained in the juice of the plant. Contact with any broken part of the plant, with leaves which have been chewed by insects, or with shoes, clothing, implement, or pets which have touched broken parts of the plant may cause a person with sensitive skin to react. Dry twigs in winter or dug-up roots in summer can often cause a reaction. Burning poison-ivy leaves and stems releases the poison in the form of tiny droplets on particles of ash and dust in the smoke, and can cause a severe reaction on exposed skin and in the breathing passages if a sensitive person breathes or passes through the smoke of such a fire. In cases of suspected contact with the plant, washing the skin and clothing with a strong soap may not prevent a reaction but will help minimize reinfection to other parts of the body or to other individuals. If a reaction does develop, one should seek the advice of a physician for proper treatment. Poison-ivy is designated as a noxious weed by the Province of Ontario, and it is the duty of every person in possession of infested land to destroy noxious weeds thereon.
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