A Field Guide to Poison Ivy, Poison Oak, and ... - Falcon Guides

The Toxic Trio 3
cation of this rule may be appropriate for the occasional
woods wanderer who is willing to remain on a beaten
path. But for the nature lover who wants to get up close
and friendly with local fauna, it is far too restrictive: Many
benign forest plants have three leaves, or three leafl ets.
As with most easy advice, in the end even the more
specifi c “leafl ets three, let it be” not only encourages
excessive precaution, it does not render absolute protection.
Both poison oak and ivy have compound leaves that
are usually arranged in three leafl ets, but they may have
up to eleven leafl ets.
The person who wants to be spared two weeks of
scratching as payment for a weekend in the country
should not only count leafl ets but also learn to recognize
leaf and plant shapes. In its usual perverse way, nature
does not make this easy. Poison ivy leafl ets are usually oval
and lightly toothed. Poison oak leafl ets are usually slightly
lobed, like oak tree leaves. Where their ranges overlap—in
the Midwest, for example—the oaks and ivies hybridize,
and newcomers may be classifi ed as both. In addition, offspring
from root stalks reproduce true to their source, but
those from seed may go their own way. As of 1986, according
to an article in Clinics in Dermatology, the poison ivy species
known as Toxicodendron radicans had nine identifi ed
subspecies (sometimes called varieties or cultivars).
Fortunately whatever the intricacies of their shapes,
the oaks and ivies are predictably similar in other important
ways. The leafl ets of both plants are usually about
four inches long. Their stems are woody. Climbing varieties
have visible aerial roots. The leafl ets are usually
shiny—sometimes described as waxy—although they may
also be dull or hairy, especially underneath. They start out
a bright green and toward late summer and fall turn yellowish
or reddish, then bright red.
When in bloom or gone to seed, poison oak and ivy
are easier to distinguish from other plants. Variations in