Sumac plants (Rhus) are common shrubs and small trees known for their striking fall foliage and prominent fruit clusters. While many varieties are harmless, the presence of one highly toxic species necessitates careful identification. The objective is to accurately differentiate safe, non-poisonous varieties from Poison Sumac (Toxicodendron vernix) to ensure safety.
Key Characteristics of Non-Poisonous Sumac
Safe sumac varieties, such as Staghorn (Rhus typhina), Smooth (Rhus glabra), and Winged (Rhus copallinum), share distinct features that set them apart from their toxic relative. These plants are characterized by large, pinnately compound leaves, where multiple leaflets are arranged along a central stem. The leaves of non-poisonous sumacs have a finely serrated, or toothed, edge along the margin of each leaflet.
A key feature for identifying safe sumacs is the presence of a terminal leaflet, which is a single leaflet at the tip of the main leaf stem. Staghorn sumac is recognized by its dense, velvety fuzz covering the new twigs and stems, resembling a deer’s antler in velvet. Conversely, Smooth sumac lacks this hairiness, having entirely smooth stems.
The fruit of non-poisonous sumacs is a significant identifier, appearing as dense, upright clusters of small, fuzzy, reddish berries (drupes) that form a pyramidal shape. These fruit clusters remain erect on the plant, often persisting through the winter, and are never white or greenish-white. These species thrive in dry, upland areas like fields, roadsides, and open woods.
How to Accurately Identify Poison Sumac
Poison Sumac (Toxicodendron vernix) poses a health risk due to urushiol oil, which causes severe skin inflammation. Unlike its non-toxic counterparts, this plant grows almost exclusively in specific, saturated environments, preferring wet or flooded soils such as swamps, peat bogs, and marshes. This habitat preference is a key indicator, as it will not be found on dry, sunny hillsides where other sumacs flourish.
The compound leaves of Poison Sumac are alternate on the stem and consist of 7 to 13 leaflets. A defining characteristic is that the edges of these leaflets are entirely smooth, or “entire,” lacking the serrations found on safe sumacs. The plant also lacks a terminal leaflet, meaning the main leaf stem ends with a pair of leaflets.
The stems connecting the leaflets (the rachis) are often reddish, a trait that becomes more noticeable as the plant matures. The most reliable visual cue is the fruit: Poison Sumac produces loose, drooping clusters of small, round berries that are white or greenish-white. These pale fruits are distinct from the compact, upright red clusters of harmless sumacs.
Plants Commonly Mistaken for Sumac
Several other plants have pinnately compound leaves that can lead to confusion with sumac, making identification of look-alikes important. The Tree of Heaven (Ailanthus altissima) is a common invasive species frequently mistaken for sumac due to its similarly structured leaves. The leaflets of Tree of Heaven are smooth-edged, except for one or two large, glandular teeth found near the base of each leaflet.
A clear distinguishing factor for the Tree of Heaven is the strong, unpleasant odor, often described as rancid peanut butter, emitted when the leaves or young stems are crushed. The fruit of Tree of Heaven appears as flat, winged seeds (samaras) that hang in cascading clusters, unlike the dense, erect berry clusters of safe sumacs.
Another plant sometimes confused with sumac is the Black Walnut (Juglans nigra), especially when young. Black Walnut has compound leaves with serrated leaflets, but the overall structure and fruit are distinct. Walnut leaflets are more finely serrated than those of safe sumacs, and the plant produces large, spherical nuts encased in a green husk.