- What does Poison Ivy (Rhus
radicans) look like? Where does it grow?
Poison ivy is a plant that has three parted compound leaves. The hard thing about saying what it looks like is that aside from this fundamental "leaves of three" is that almost every other descriptor is variable. The leaves may be stiff and leathery, or thin and supple. The leaves may be somewhat hairy or completely hairless, they may be shiny or dull. The leaf edges may be toothed, wavy or neither. The plant grows as a vine, a small freestanding plant or as a dense shrubby thicket which may reach heights of five to ten feet! The one good point in all of this uncertainty is that few other plants have three parted compound leaves! So, if you see "leaves of three", as the adage goes, "leave them be!"
Poison ivy can be found growing in open woods (you can see it all along the Nature Trail!), in thickets, in fence rows, along roadsides and in sites that have been disturbed or which are undergoing active early succession. Human activity seems to encourage and facilitate its growth and dispersion
- Why do some people "break out" from contact with poison ivy and other people do not?
The skin reaction (redness, itching, blistering etc) that a person experiences after they come into contact with the leaves, stems, flowers, pollen or fruit of the poison ivy plant are the result of an allergic reaction within the body of the affected individual. The actual chemical that is triggering this allergic reaction is a volatile oil
(urushiol) that is found in all parts of the plant. Only those individuals that have the poison ivy allergy (and these are people who have been previously exposed and sensitized to this volatile oil) will have the allergic reaction. Almost everyone, though, who comes in contact with this oil will eventually become sensitized and allergic.
- What good is poison ivy?
Poison ivy is a very widespread and productive plant. It flowers in May and June and produces dense clusters of white berries that ripen between August and November and often persist through the winter. Over sixty species of birds have been documented to eat the berries of poison ivy! These birds, apparently, do not become sensitized to the volatile oils and do not experience allergic reactions to the plant. As mentioned in the "Winter Bird" section of this web site, poison ivy berries are an important natural food source for the over-wintering birds on the Nature Trail.
A secondary consequence of birds' eating the poison ivy berries is the passage of the poison ivy seeds through the birds' digestive systems. The seeds, then, are energetically dispersed throughout the active range of the birds.
- What is "poison oak"?
"Poison oak" is, according to most authorities, really just a kind of poison ivy and not some separate plant species. It is always an erect plant, typically has lobed, "oak-like" leaves and is found classically in coastal and southern locations throughout the United States. If you are sensitized to poison ivy, you will "get" poison oak.