Poison Oak has two distinct species. Both types have fuzzy-looking leaves in clusters of three. The leaves look a little like the leaves of the oak tree. Eastern poison oak grows from New Jersey to Florida and as far west as Texas and Kansas. Western poison oak grows along the Pacific coast from Washington state to Mexico.

There are two closely related species of Poison Ivy. It grows almost everywhere in the United States except Nevada and parts of California. Poison ivy may look like a vine climbing up a tree, a bushy shrub or even a small tree. Poison ivy's leaves generally grow in bunches of three and, in the last summer and fall, there may also be tiny white berries growing in bunches from the stems. Poison ivy rarely grows at altitudes higher than 5,000 feet.

Poison Sumac's three- to four-inch-long leaves grow in clusters of seven to 13 leaves. The leaves are orange in spring, green in summer, and red, orange, or yellow in fall. The plants can grow as tall as 15 feet high. Poison Sumac grows in bogs, swamps and wet bottom land east of the Mississippi River. Poison sumac plants usually have red stems, may have long clusters of whitish berries in the summer and fall.  (((See the picture section of this article, editor)))

AND FINALLY:

Hi Bob:

Thought I'd send this on to you in case you wanted to do further
research. The poison ivies used to be Rhus toxicodendron, R.
quercifolium, and R. vernix. Botanists came through about 10 years back
and re-classified everyone to new names:

Rhus toxicodendron became:
        Toxicodendron radicans subsp. eximium
        Toxicodendron radicans subsp. negundo
        Toxicodendron radicans subsp. pubens
        Toxicodendron radicans subsp. radicans
        Toxicodendron radicans subsp. verrucosum
        Toxicodendron ridbergii

Rhus quercifolium became:
        Toxicodendron toxicarium

Rhus vernix became:
        Toxicodendron vernix

These Toxicodendrons are all listed by Useful Wild Plants as being found
in Texas, as well as extensive ranges outside the state. You would
probably want to search primarily on Toxicodendron, but there may be
some layman pages still using the old taxonomy of Rhus. It's an itchy
subject.

Tomye Zettner
 

THANKS TOMYE! for all of your help with this topic.
Tomye Zettner lives in Luck Texas and is an expert on the Indigenous 
Plants of Texas.