Poison ivy (Toxicodendron radicans) grows where there is little canopy. The plant needs mottled light in order to survive. Look for it in the pine flatwoods region of the Hammock Trail.

This plant can grow as a trailing vine, a scrub, and as a climbing vine that attaches itself to trees by sending out numerous rootlets. Because Naples, Florida has a 365-day growing season, huge vines of poison ivy can develop.

A good way to identify poison ivy is: “Leaves of three, let them be.” As shown in these photographs, its three leaves are alternate and compound. Each leaf has three almond-shaped leaflets connected with a common petiole that is usually red. Each leaflet has few or no teeth along its edge and its surface is smooth. Leaf color can be light green, dark green, or red, depending on the age of the leaf and the season of the year. Mature leaflets are shiny.

Poison ivy spreads either vegetatively with rhizomes (modified subterranean stems) or with seeds. It flowers from May to July. Flowers are five-petaled, yellowish or greenish-white, and located in clusters above the leaves. As shown at right, the fruit is a green berry. Berries mature August to November, becoming a gray-white color. Inside the berry are seeds. Since the berries are a favorite winter food of birds and other animals, seeds are spread in the animals' excreted wastes.

The genus name Toxicodendron means "poison tree." The plant's sap contains urushiol, a clear oily organic allergin that when touched, produces an itchy rash that blisters. Leaves release urushiol when they are bumped, torn, or brushed against.