Poison ivy leaves from the compound toxicodendron and have three or more odd numbered leaflets. Flowers and fruits arise in the axillary position in the angle between the leaf and the twig from which it arises. The leaf stock is large at its origin, from the supporting twig and leaves a U or V shaped scar after falling off. Green fruit turns off white when it matures. Plants cling to trees via hairy aerial rootlets. There are two species of poison ivy and poison oak, and one species of poison sumac that is common in the United States. Some have multiple subspecies. Poison oak and poison ivy are weeds that grow along roads, trails, rivers, or streams, and usually have three or five leaflets per leaf. Poison sumac has 7 to 13 leaflets per leaf. Younger leaves are usually more red in appearance, and mature fruit known as droops are cream or tan colored and hairless, while the young fruit has hair. Poison ivy classically has pointed tips and is ovate with the widest point below the interim. Poison oak leaves usually have round edges. Western poison oak has oval leaves while Eastern poison oak has a variable appearance that mimics white oak.
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