Description
Poison-ivy (Rhus radicans L.) is a climbing plant of the sumac family and can be found in every province except Newfoundland. It grows on sandy, stony or rocky shores, sprouts in thickets, in clearings and along the borders of woods. This glossy perennial can spread by seed or by producing shoots from its extensive underground stems (rhizomes).
The sap of the plant contains an oily resin that causes an irritating inflammation of the skin in most people. All parts of the plant, including the roots, contain this poisonous resin. Most people develop symptoms 24 to 48 hours after contact. The extent of a reaction depends on the individual’s sensitivity and the amount of sap in contact with the skin.
The compound leaves of poison-ivy consist of three pointed leaflets; the middle leaflet has a much longer stalk than the two side ones. The leaflet edges can be smooth or toothed but are rarely lobed. The leaves vary greatly in size, from 8 to 55 mm in length. They are reddish when they emerge in the spring, turn green during the summer, and become various shades of yellow, orange or red in the autumn.
The plant stems are woody and of two kinds. The most frequent kind grows as a trailing vine, with upright leafy stalks 10 to 80 cm high. The second kind is an aerial vine that may climb from 6 to 10 m high on trees, posts or rough surfaces.
The plant produces clusters of cream to yellow-green inconspicuous flowers during the months of June and July. The berries that appear by September are clustered, globular, waxy, and green-to-yellow in colour. The size of the berries ranges from 3 to 7 mm in diameter. They often remain on the low, leafless stems of the plant all winter.
Effects of Poison-Ivy
The oily resin can be found in the roots, stems, leaves and fruit. It causes an irritating inflammation of the skin, called Rhus-dermatitis or poison-ivy dermatitis. The inflamed areas frequently develop blisters which are accompanied by intense itchiness. Contact with any broken part of the plant may cause a reaction in some individuals. The rash spreads by exposure to the sap and not from the sores themselves. Therefore, an individual has to actually come into contact with the sap before developing an allergic reaction.
Treatment in Case of Skin Contact
Areas of skin that are suspected of contamination should be carefully washed with soap and cold water. Cold water should be used because hot water tends to open the pores of the epidermal layer; the heat would increase the chances of the resin being deeply absorbed into the skin. If soap is not available, vinegar (2 tablespoons in 1 cup of water) or alcohol (1/2 cup to 1/2 cup of water) can be substituted.
It is important to note that these practices may not prevent a reaction, but will likely prevent the infection from spreading.
If a reaction does develop, one should seek the advice of a physician for proper treatment. Skin irritation (itching, red inflammation, blistering of the skin and, in severe cases, oozing sores) resulting from exposure to poison-ivy normally disappears in a week to 10 days.
Similar Plants
Poison-ivy is often mistaken for similar plants such as poison oak and poison sumac. These can also cause Rhus-dermatitis. When in doubt, avoid touching an unknown plant until it has been clearly identified.
Control of Poison-Ivy
Remember: always wear gloves.
Protective Clothing
When working in or near poison-ivy, always wear protective clothing to ensure
that no area of the skin is exposed to the sap of the plant. Poison-ivy sap
can adhere for long periods to clothing, tools, and the hair coats of pets
and livestock. Under hot, humid conditions the sap becomes inactive in about
a week. If conditions are dry, it can retain its harmful effect for a long
period.
Any clothing worn while working in or near poison-ivy should be carefully
removed, washed in hot, soapy water, and hung outside to dry for several days.
Remember to wear gloves while handling objects that may be contaminated. Do
not wash clothing suspected of contamination with other laundry in order to
avoid any further contamination. Repeated washing may be necessary.
Cultivation
For effective control of poison-ivy, the reproductive capacities of the plant
can be disrupted by destroying its roots and stems. By digging out and hand
picking the roots and stems, and working the soil frequently, the ability
of the plant to produce shoots will be minimized. Repeated cultivation will
eventually eliminate poison-ivy because the plant does not regenerate easily
from plant fragments. Since loose seeds may be difficult to detect, remove
any dead plant material from the ground in case some seeds are still attached
to the stems.
Chemical Control
Applying herbicides to control poison-ivy can be effective. One single treatment
may be sufficient but it is possible for regrowth to occur. It may be necessary
to repeat the treatment as often as regrowth appears.
Applying herbicides by spot-treatment will help to minimize the chances of
the product drifting onto desirable vegetation. Herbicide spot treatment is
also advisable when poison-ivy is a lawn weed.
Available Herbicides
Domestic class products available to homeowners for the control of poison-ivy
will usually contain one, or will consist of a mixture, of the following
active ingredients: amitrole, simazine, ammonium sulfamate, glyphosate, 2,4-D,
mecoprop, or dicamba.
Domestic pesticides can usually be purchased through garden centres or hardware
stores.
Purchase only those products whose labels indicate poison-ivy control.
Disposal of Poison-Ivy
CAUTION: DO NOT BURN POISON-IVY as this may release the
poison in the form of tiny droplets carried by the ash and dust particles in
the smoke. A severe reaction may occur if a sensitive person inhales or is
exposed to this smoke.
Dead poison ivy plants can still cause dermatitis and must be handled with
care. Dispose of them by placing them in a garbage bag. Make sure that bags
containing poison-ivy remains are well identified and disposed of with the
household garbage.
Another method is to bury the remains deep into the ground. Sufficient depth
is important to ensure there is no regrowth.
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