Poison sumac (Toxicodendron vernix) is a highly toxic plant native to North America. All parts of the plant contain urushiol, a potent oil that causes severe allergic reactions, including intense skin redness, itching, and blistering. Recognizing its physical dimensions and features is the primary way to avoid the painful rash it causes.
Growth Habit and Maximum Size
Poison sumac typically grows as a multi-stemmed, erect shrub, but it can mature into a slender, small tree under favorable conditions. The average mature height is 5 to 6 feet, forming an open, somewhat sparse crown.
Under ideal conditions, particularly in deep, nutrient-rich wetlands, the plant can reach up to 20 to 25 feet tall. Unlike poison ivy and poison oak, this species does not grow as a vine or climb, maintaining a distinct, woody, self-supporting structure.
Distinctive Physical Features
The plant is identified by its large, alternate, compound leaves, which have 7 to 13 oval leaflets arranged opposite each other along a central stem (rachis). The leaflets have smooth, “entire” edges and pointed tips, lacking the serrations found on many harmless sumac varieties. The rachis is frequently reddish.
The foliage is glossy green in summer but turns brilliant orange-red in the fall. The bark on the stems and trunk is generally smooth and light grayish-brown. The fruit develops from small, greenish-yellow flowers that appear in loose, drooping clusters (panicles). The resulting small, round drupes mature to a pale yellowish-white or grayish color, hanging in slender, drooping clusters that often persist into the winter.
Preferred Habitat and Distribution
Poison sumac requires specific environmental conditions, found almost exclusively in wet, highly saturated, and often acidic soils. It rarely grows in dry, upland areas. Common locations include freshwater swamps, bogs, marshy areas, and thickets along the edges of rivers or ponds.
Its geographic range covers the eastern United States and parts of eastern Canada, extending from Maine down to Florida and west to Texas and Minnesota. The plant is most abundant within the coastal plains and the Great Lakes regions, where high moisture and ideal soil conditions allow it to reach its maximum height potential.
Differentiating from Harmless Lookalikes
Distinguishing Toxicodendron vernix from harmless sumac species (Rhus genus), such as Staghorn Sumac or Smooth Sumac, is crucial for safety.
Fruit and Leaf Structure
The most reliable differentiator is the fruit: harmless sumacs produce dense, upright, cone-shaped clusters of bright red berries. Poison sumac produces whitish, pale yellow, or gray fruit clusters that always droop downward from the stem.
Poison sumac leaves have smooth, “entire” edges and 7 to 13 leaflets. Harmless sumacs usually have a higher leaflet count (11 to 31) and their leaflet edges are distinctly serrated or toothed.
Habitat and Stems
The general growth location helps identification. Harmless sumacs frequently colonize dry, disturbed soils along roadsides or in fields. Finding a sumac plant growing directly in a swamp, bog, or standing water is a strong indication that it is the toxic variety. Finally, the twigs of non-poisonous Staghorn Sumac are covered in dense, velvety hairs, while poison sumac’s stems are typically smooth.