"Leaves of 3, let them be." This rhyme pertains both to poison ivy identification (for poison ivy pictures, click "More Images" under the picture at right and see Page 3) and poison oak identification. The rhyme does not, however, pertain to poison sumac identification (i.e., the shrub, Rhus vernix; see my pictures). But people are far more likely to come into contact with the other two members of the triad than with Rhus vernix (there is also a non-poison sumac). All three are indigenous to North America.
In the U.S., poison ivy (Rhus radicans) grows everywhere but on the West Coast, while another vine (sometimes shrub), poison oak (Rhus diversilobum) grows primarily on the West Coast. In plant taxonomy, all three are sometimes classified as Toxicodendron rather than Rhus ("Toxicodendron" is from the Greek and literally means "poison tree"). Below, I speak mainly of Rhus radicans, but most of the facts related here also pertain to poison oak. For pictures of poison oak, see "Poison Oak Pictures" in the sidebar near the bottom of the page. I also offer information on how to get rid of poison oak.
The trademark grouping of three leaflets on Rhus radicans mentioned earlier assumes a reddish tinge when the leaves first come out in the spring, but the leaves turn green in the summer. Although the color (white) of its berries is often mentioned as a method of poison ivy identification, it is not as reliable as is identification by leaf. The berries, after all, are produced only at the end of the growing season; knowing about the berries would do you little good when attempting identification in the spring. Incidentally, poison oak and poison sumac also have white berries. The non-poisonous varieties of sumac have red berries.
Picture, Description of a Plant That "Mimics" Rhus radicans
In the eastern U.S. another wild vine flourishes that is often mistaken for Rhus radicans -- Virginia creeper (Parthenocissus quinquefolia). I provide a picture of Virginia creeper, elsewhere; it is also included in my "Pictures of Poison Ivy" gallery. But Virginia creeper more often has five leaves to a branch rather than three; and its leaves are more toothed than are the leaves on Rhus radicans. The fall foliage of this vigorous grower is truly spectacular.
While Virginia creeper vines do not contain urushiol oil, the compound that makes Rhus radicans toxic, you may need to shun contact with Virginia creeper, too. It turns out that the Virginia creeper's sap contains oxalate crystals, which can be toxic to some people. If you're unsure as to whether you're one of those people, don't touch Virginia creepers, since the result of contact could be a skin rash.
Like Virginia creeper, the fall foliage of Rhus radicans is surprisingly spectacular (for a poison ivy picture displaying fall foliage, see Page 3). One is tempted to ask, How can something that has caused so much suffering be so beautiful? The green summer color of the plant's leaves yields to brilliant fall foliage in red, yellow or orange. Their autumn brilliance is due to the anthocyanin pigments characteristic of the plant family to which they belong, namely, the cashew family (Anacardiaceae).
But if you're reading this article while plagued with the itching that the plant brings, you'll be much more interested in hearing some treatment tips than about how pretty the plant looks in the fall. And treating poison ivy rash is the subject of Page 2....