Poison Ivy


Poison ivy (Toxicondendron radicans) is not an invasive plant from another country. Its habitat covers the United States coast to coast, southern Canada, and on into Mexico. However, its growth spreads easily, and as a source of an oil (Urishiol) that can cause an irritating skin rash is effective in limiting access to wide areas. Poison ivy forms off-white fruits in the fall that are food for birds, the principal means of transference to other sites. The name is a little misleading since this ivy can grow as a ground cover about a foot tall, a freestanding shrub several feet tall (commonly called poison oak), or as a vine attached by thin aerial roots to a tree or other object. In Marblehead poison ivy can be found as a ground cover and as a vine on trees in all conservation areas. It is a good idea to learn to recognize and steer clear of it.

Thin aerial roots attaching a vine to a tree identifies this as poison ivy.

A combination of the ground cover and vine forms is not uncommon.

A characteristic of poison ivy in each of its plant forms is a compound leaf. At the end of each leaf stalk is a trifoliate pattern of three separate leaflets one at the end on a longer attachment to the main stalk than the other, lower, two. Each main leaf stalk connects to the principal vine in an alternating pattern.

Juvenile leaves appear first as pale green, changing to a deeper green with maturity.

In the fall, the leaves turn varying shades of red and yellow.
Citation – Ted Bodner, Southern Weed Science Society, Bugwood.org

Some colors can be quite vivid.

Other colors can be mixed and muted.

The oil Urishiol is in all parts of the plant. A person’s skin coming in contact with the plant, even when the plant is dead, can result in a range of reactions depending on the person’s sensitivity. Washing quickly and thoroughly with soap and water can minimize a reaction.

  3 Responses to “Poison Ivy”

  1. Poison Ivy does not belong on this list because it is native; see http://www.massnrc.org/MIPAG/

    We have 2 species of Poison Ivy in Massachusetts, both of which are listed for Essex County in Vascular Plants of Massachusetts: A County Checklist, Cullina et al. 2011, MA Div Fisheries & Wildlife

    Poison Oak does not occur in MA; its nearest occurrence is in NJ: http://plants.usda.gov/core/profile?symbol=TOPU2

    Another authoritative source for info about plants of MA is Flora Novae Angliae, A. Haines, 2011, NE Wildflower Society

    A list of harmful and/or nuisance plants would be appropriate and useful for this site; native plants should not be included with invasives.

  2. On-line plant ID help, NE-based & current, is at https://gobotany.newenglandwild.org/

  3. It’s my understanding that washing with soap and water will spread the nasty oil unless you wash with a dishwashing detergent designed to cut grease. (Think of removing chicken grease or butter.) I’ve read that one can use rubbing alcohol to remove the oil before washing with detergent. I haven’t tried this but it makes sense. It’s worth noting that the oil can be transferred from clothing, shoes, or pets to your skin, and that it has a shelf life measured in years.

    Thank you for the great pictures and information.

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