Over 25 varieties of ivy are grown in the United States, but English ivy (Hedera helix) is the most popular, according to the University of Florida IFAS Extension. Other ivies used in landscapes include Boston, Algerian and Persian. These ivies, while similar, have distinctive differences in the size, shape and color of their leaves. Poison ivy generally grows in woodland settings, but occasionally makes an appearance in backyards. Proper identification of this plant minimizes the chances of a painful rash.
When identifying ivy by its leaves, consider first its growth. English ivy is evergreen, producing dark green or variegated leaves throughout the year. Lesser known Algerian and Persian ivies are also evergreen, according to Clemson University. Boston ivy is a deciduous vine, turning red or purple in the fall and losing its leaves. The leaves of poison ivy turn red or yellow and drop in the fall, as well.
English, Algerian and Persian ivies produce lobed leaves that may be wide and deeply lobed or narrow, with finely cut lobes. Boston ivy and poison ivy are sometimes mistaken for one another because both produce clusters of three leaflets. Poison ivy leaves may be toothed or smooth.
The size of ivy leaves range from dwarf varieties (such as Conglomerata with tiny leaves between 1 to 2 inches long) to larger varieties (such as the Persian ivy whose leaves are 3 to 7 inches long and 10 inches wide). The leaves of most English and Boston ivy varieties are between 2 and 4 inches wide. Poison ivy leaves also generally grow 2 to 4 inches wide.
Consider the growth pattern of ivy leaves to identify it. English, Persian and Algerian ivy may grow as a creeping mat on the ground or may climb structures with aerial roots. English ivy can be trained into elaborate topiary structures. Poison ivy may grow as a vine or a low-lying shrub. The vine varieties may often appear hairy. Boston ivy is generally used as a climbing vine, with leaves quickly covering doors, windows and structures if uncontrolled.
Two ivy types have warnings attached. The leaves of poison ivy produce uroshiol, a chemical that causes intense itching, rashes and blisters. The chemical remains active on shoes, clothing and sporting equipment for up to two years after initial contact, causing inflammation if touched. English ivy, according to the Kings County Washington website, is an invasive plant in the Pacific Northwest. It thrives in the mild, moist conditions found there and out competes most native species. The densely matted leaves hide rodents, damage trees and exacerbates soil erosion on slopes.