Weed of the Month- October

Poison Ivy (Toxicodendron radicans)  

(Provided by Master Gardener, Peter Russell)

Family: Anacardiaceae

Native Origin: Native, toxic, common throughout Connecticut.

Life Cycle: Poison ivy is a perennial weed reproducing by seeds and creeping stems and rootstocks. It emerges in early spring, and the leaves last through late fall. 

Description: Poison ivy is a woody plant with varying growth patterns and leaf characteristics. It is usually found in vine form but it can also grow as a shrub, climbing vine with aerial roots, or lay prostrate on the ground. Stems are capable of forming roots and sending out new shoots when in contact with soil.   

Habitat: Poison ivy is common throughout Connecticut especially in dry, rocky soil, in thickets and along fields, woods, roads, and paths. Poison Ivy can thrive in both moist soil and dry sites on the most exposed hillsides.

Stems: Woody stems have gray bark and grow either horizontally along the soil surface with upright leafy stalks or as a climbing vine.

Leaves: Leaves are arranged alternately along the stem and have a compound leaf structure with three leaflets. The center leaf has a longer stalk than the two lateral leafs. The edges of the leaves can be smooth, toothed, or somewhat lobed. In early spring, emerging leaves have a reddish color becoming shiny green after a while. In the summer, the leaves will often be a dull green color turning yellow or scarlet red in the fall. Poison Ivy leaves may even be somewhat hairy, especially on their lower side.

Flowers and Fruit: The flowers and fruit are always in clusters on slender stems that originate in the leaf axil. The flower is five-petaled, yellowish green to green in color appearing May through July. The fruits are small, round, and usually have a white, waxy appearance appearing in late summer and often persisting all winter.

Control and Management: In an area that can be mowed, poison ivy can be controlled by close mowing. Repeated mowing will be required to kill and starve out the stem and root. Digging up roots is not as effective as mowing because any small root left behind will grow. For the hairy vines climbing up trees, cut through the vine stopping at the bark of the tree. Continuously cut off any regrowth of leaves from the remaining stump.

Wear protective clothing, long pants, long sleeves, and gloves to keep skin from coming in contact with the irritating poison ivy oils. Wash clothes and gloves in hot soapy water immediately to avoid future contact with the oil on the clothing. Clean all tools used in cutting vines or digging out roots.
A non-selective systemic herbicide can be used to control/kill poison ivy according to label instruction. Use it with caution, as it will kill everything it contacts. Treatments should be made in late summer or early fall, when the plant is storing carbohydrates in the root systems.


UConn Home and Garden Education Center 2016
Ohio State University-Ohio Weed Guide