Western poison oak(Toxicodendron
diversilobum)
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Considered the poison oak by some botanists, this plants is
common on the Pacific Coast (except for the Olympic
Peninsula) from southern British Columbia to northern Baja
California. Its three leaflets seem randomly lobed and
resemble oak leaves. Most often found as a spreading,
freestanding shrub two to six feet tall, Western poison oak
can also take the form of a tall, climbing vine.
Eastern poison oak(Toxicodendron
toxicarium; also T. quercifolium)
Unlike poison ivy, this low shrub never climbs or produces
aerial rootlets. It grows in poor, sandy soils such as
those of oak-pine savannas in the Atlantic and Gulf coastal
plains and in scrub oak forests in Arkansas and Missouri.
The plant's three leaflets are distinctly roundlobed and
resemble the leaves of the common, nontoxic white oak tree.
Eastern poison oak berries are white and are borne in
clusters.
Poison sumac(Toxicodendron
vernix)
This tall shrub prefers low, damp, swampy places and may
grow to 15 feet. Like its nonpoisonous sumac cousins, it
has compound leaves with multiple leaflets, but there the
similarities end. Poison sumac leaves generally have seven
to 13 smooth-edged leaflets; nonpoisonous sumac leaves have
11 to 31 toothed leaflets. Poison sumac yields pale-yellow
or cream-colored berries that hang in drooping bunches;
nonpoisonous species produce upright, conical clusters of
red fruit in typical "staghorn" fashion. Poison sumac is
closely related to the Asiatic lacquer tree, and it is
sometimes known as "poison dogwood."
Common poison ivy(Toxicodendron
radicans)
Poison ivy is found throughout the U.S., except for some
desert areas, as well as much of Canada and Mexico. It can
be a shrub, ground cover or woody vine covered with hairy
aerial rootlets. Generally, in Eastern states the plant's
three leaflets are smooth-edged, while varieties in Central
and Southeastern regions have notched or toothed leaflets.
Some Western varieties have a distinct lobe or "thumb" on
one or both sides of each leaflet. In spring, young leaves
often appear glossy and reddish but then turn dull green.
Emergence of foliage is followed by greenish white to pale
yellow flowers that later yield clusters of small,
yellowish-to-white berries.
