Poison ivy (Toxicodendron radicans) is a highly successful plant that thrives as ground cover, a small shrub, or a climbing vine. It definitely climbs trees, sometimes reaching impressive heights exceeding 75 feet within the host tree’s canopy. The plant contains urushiol, an oily resin found in all parts—leaves, stems, and roots—which causes an allergic skin reaction in most people.
The Climbing Mechanism
Poison ivy achieves vertical ascent using adventitious roots, also called aerial rootlets. These small, thread-like roots emerge directly from the vine stem and attach the plant to the rough surface of a tree trunk or other upright structure. The rootlets provide mechanical adhesion and support; the vine does not draw water or nutrients from the host tree.
As the vine matures, these rootlets proliferate, creating a dense, matted layer that gives the stem a characteristic “hairy” appearance. This robust adhesion allows the vine to grow straight up, unlike other climbing plants that spiral.
Identifying the Mature Vine
The mature poison ivy vine, often called the “hairy rope,” has distinct visual cues. The most notable feature is the thick, woody stem covered in a dense growth of reddish-brown or gray root hairs. This “hairy” texture is a reliable identifier, particularly during the dormant season when leaves are absent.
The leaves emerging from the vertical stem maintain the well-known “leaves of three” structure. Each leaf is composed of three leaflets, with the center leaflet on a slightly longer stalk. When growing high on a tree in full sun, the leaves can become large, glossy, and may have smooth, toothed, or lobed edges. During fall and winter, clusters of opaque white or yellowish berries may also be present along the stem.
Increased Exposure Risk from Vertical Growth
The vertical growth of poison ivy significantly increases the risk of human exposure to urushiol oil. As the vine climbs high into the canopy, the oil can drip or flake off, contaminating the bark of the host tree below. This creates a contact risk even without touching the vine’s foliage directly.
The danger persists year-round because urushiol remains active in all plant parts, including the vine stem and roots, even after leaves drop in winter. Individuals gathering fallen wood or clearing brush are susceptible to exposure during the dormant season if they handle contaminated wood. Objects that rub against the vine, such as pets or gardening tools, can also transfer the oil indirectly, causing an allergic reaction.
Safe Removal of Climbing Poison Ivy
Removing a mature vine requires careful action to minimize contact with urushiol oil. The safest approach is to cut the main vine stem at the base, near ground level, using loppers or pruning shears. Remove a section about a foot long to ensure the top portion is severed from the roots.
The cut vine section still attached to the tree should be left in place to die naturally. Attempting to pull it down can shower the area with oil and potentially damage the tree’s bark. The stump remaining in the ground should be treated immediately with an herbicide, such as glyphosate or triclopyr, applied directly to the cut surface. Never burn the cut vines or any part of the plant, as the smoke carries urushiol particles that can cause severe respiratory irritation if inhaled.