Poison Ivy Vines in the Landscape

Robert J. Souvestre  |  7/21/2011 7:26:56 PM

As leaves grow upward on tree trunks and fences, Poison Ivy leaves become larger and in later summer they will have bumps. Don’t confuse with another common vine, the 5-leaved Virginia Creeper.

Identification Tips: "Leaflets Three -- Let It Be" and tiny roots growing along the stem.

Poison ivy is abundant in urban, suburban and rural landscapes. Keep a sharp eye out for this plant because one out of every two Americans is allergic. Promptly and ruthlessly deal with any plants as soon as you see them.

Poison ivy is a tall, climbing vine that is leafless – or deciduous – in winter. As it climbs tree trunks, wood fences or other flat structures, the stem produces many small roots that cling to the surface. This is a good identifiable characteristic of the vine in case you can’t easily see the leaves. Plants are very common along fences and at the base of trees and seedlings are often found in garden beds.

Poison ivy has a characteristic compound leaf consisting of three leaflets. Hence the saying, “Leaves of three, let it be.” The leaves are 2 to 4 inches long and dull or glossy green with pointed tips. The middle leaflet is generally larger than the two laterals. Young foliage is often shiny or oily-looking with a reddish tint.

Mature poison ivy vines growing up trees flower and produce a white fruit that’s readily eaten by birds. The birds spread the seeds through their droppings, causing the wide occurrence of this plant. New seedlings of poison ivy are easily overlooked. They may have a reddish tint to their foliage and will appear upright. It is easy to come into contact with young poison ivy seedlings when weeding flower beds, so you need to be observant.

Three methods can be effective in eradicating poison ivy in landscapes.

The first is hand pulling or digging it out when the soil is moist, getting out as much of the roots as possible. Place the plants into a plastic bag and throw it away.

The second method is to carefully spray the foliage with a systemic herbicide. This is only possible when the spray will not get on the foliage of desirable plants. If needed, nearby desirable plants can be covered with plastic sheets or bags to protect them while you do the spraying. Be sure to wet the foliage of the poison ivy vine thoroughly. Spray on windless mornings.

Systemic herbicides are absorbed by the foliage and enter the plant’s circulatory system, sending the material into the vine’s roots and killing them. Glyphosate (Roundup, Eraser, Hi-Yield Killzall and other brands) or triclopyr (Brush-B-Gon, Brush Killer, Greenlight Cut Vine and Stump Killer and other brands) are commonly recommended for poison ivy control. Herbicides that contain a combination of dicamba (Banvel) and 2,4-D also work well. Once the vine dies it may be removed. The dead leaves still contain the rash-causing oils and should be handled cautiously with gloves.

The third method of removal is for larger, established vines growing up in trees or intertwined in shrubs. Spraying the vine foliage is not practical in these situations because of the potential to injure desirable trees and surrounding landscape plants. Poison ivy control in sensitive areas can best be achieved by the cut-vine method.

Cut off the vine a few inches from the ground with loppers and immediately treat the surface of the freshly cut stump with undiluted triclopyr. The vine in the tree or shrub will die because it has no root system. The treated stump will die because the herbicide gets absorbed by the freshly cut surface and translocates to the roots. Applying the herbicide to the fresh cut is necessary because it prevents the stump from resprouting. This method is very effective and may be used any time of the year.

Getting poison ivy off your property will probably take repeated herbicide applications. Older vines in neighboring yards may continue to drop seeds in your landscape. Watch out for this unwelcome plant and be prompt and aggressive in your efforts to control it.
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