Smooth Sumac
Rhus glabra
Cashew family (Anacardiaceae)

Description: This native woody shrub is 2-10' tall, branching occasionally. Sometimes it develops into a small tree up to 20' tall, but this is uncommon. The compound leaves are oddly pinnate, consisting of 9-27 leaflets; they alternate along the woody stems. The leaf stalks are hairless and have a whitish bloom. Each leaflet is up to 4" long and 1½" across, lanceolate, and hairless, while the margins are serrated. The upper surface of a leaflet is green, while the the lower surface is white with exposed veins. During the fall, the leaflets become brilliant red. The upper branches produce one or more erect panicles of flowers up to 1½' long and and ½' across. Each flower is about ¼" across, consisting of a yellowish or whitish green corolla that is divided into 5 spreading lobes, and subtended by a star-like green calyx with 5 pointed tips. There are both male and female flowers. The blooming period occurs during early to mid-summer. The flowers are replaced by round drupes during the late summer, which persist through the fall and winter. These drupes are individually about 1/6" long, and covered with short acrid hairs; they are brilliant dark red, gradually turning black during the winter. A single stony seed occurs inside each drupe; it is kidney-shaped and has a smooth surface. The root system consists of a taproot and spreading rhizomes; this shrub often forms vegetative colonies.

Cultivation: The preference is full sun to light shade, and moist to dry conditions. The soil can consist of loam or clay loam; some rocky material is also acceptable. Smooth Sumac often grows in soil with a higher pH than other sumacs. It is an easy plant to grow from large transplants, but often becomes aggressive.

Range & Habitat: Smooth Sumac occurs in every county of Illinois; it is a common plant (see Distribution Map). Habitats include edges of moist to dry black soil prairies; upland forests with a history of disturbance; thickets and woodland borders; limestone glades; fence rows and abandoned fields; areas along roadsides and railroads; and miscellaneous waste places. This is one of the shrubby invaders of prairies; it is a pioneer species. This shrubby species can recover from infrequent fires or mowing, and resists herbicides.

Faunal Associations: The flowers attract short-tongued bees, wasps, and flies, primarily. Among the flies, are such visitors as soldier flies, Syrphid flies, dance flies, bee flies, thick-headed flies, Tachinid flies, Anthomyiid flies, and others. Occasionally, long-tongued bees, small butterflies, and beetles may visit the flowers. These insects seek nectar primarily; bees also collect pollen. The caterpillars of the butterfly Celastrina argiolus (Spring/Summer Azure) feed on the foliage, while the caterpillars of the butterfly Calycopis cecrops (Red-Banded Hairstreak) feed primarily on fallen foliage. Several species of moths also feed on Smooth Sumac (see Moth Table). Both upland gamebirds and songbirds eat the fruit (see Bird Table), which may persist through the winter. Some mammalian herbivores browse on Smooth Sumac, including the Cottontail Rabbit (bark, fruit) and White-Tailed Deer (twigs, foliage).

Photographic Location: Photographs were taken in an area along a railroad near Champaign, Illinois.

Comments: Smooth Sumac is quite attractive during the fall. It is easily distinguished from other sumacs by its absence of hairs, lack of winged leaf stalks, or greater number of leaflets. A sapling of Ailanthus altissima (Tree-of-Heaven) somewhat resembles Smooth Sumac, but the former has leaflets with green undersides and less serration.