Trees and Shrubs of the Eloise Butler Wildflower Garden

Smooth Sumac is a native large shrub that given space, can become a small tree, 10 to 15 feet high. When growing in thickets, the tallest stems will be at the back with decreasing stem height forward, providing sunlight to all plants.

The alternate leaf is 16 to 24 inches long, pinnately divided into 11 to 31 leaflets, very pale underneath, dark green above, and often toothed. The leaf stem (rachis) without fine hair. Leaflets are narrowed or rounded at the base, sharply pointed at the tip. Unlike Staghorn Sumac, twigs are smooth, have spots and are not hairy. The leaves in the autumn turn a brilliant red and may often be seen turning color in late summer.

The inflorescence is a compact, pyramid shaped 8 inch high panicle of short stalked flowers at the end of the branches. Stalks of the inflorescence may have some fine hair, unlike the twigs.

The flowers are usually separate by sex, rarely perfect. The small 5-parted flowers are greenish-yellow with 5 sepals to the calyx with the lobes opposite the petals. The 5 petals are widest in the middle, have bluntly rounded tips and reflex when the flower opens. The staminate (sterile) flowers have 5 stamens placed alternate with the 5 petals. The filaments are yellowish green, the anthers yellow, oblong, with 2 cells. The sterile flowers have a smaller but imperfect ovary. The fertile flowers (pistillate) have a larger ovoid 1-celled ovary with 3 short styles. Fertile flowers usually show stamens that are functionally sterile and shorter than those in the staminate flowers. At the base of the ovary but not attached to it, in both sterile and fertile flowers, is a yellow to reddish nectary disc.

Fruit will appear on plants 3 to 4 years old. Smooth Sumac and Staghorn are very similar in that the fertile flowers mature in late summer into a red hairy fruit 1/8 to 1/4 inches in diameter, called a drupe, which contains one ellipsoid shaped, slightly flattened, greenish-tan hard seed, 3 mm long. A cluster may contain 100 to 700 seeds. Most plants contain only male or female flowers, thus only the fertile female plants will produce seeds, although some plants may have both flowers. The fruit clusters, if not eaten in season will often be visible over winter and in spring before leaf out, thus providing winter interest. The fine hair on the drupes is acidic.

Habitat: Sumac habitat is usually open fields and roadways, where there is sunshine and the soils are not wet. It will be crowded out by trees and larger shrubs. Sumac fruit is a winter emergency food for large game birds and many songbirds have sumac in their diet. Deer will browse the stems and fruit. Thickets are established from root sprouts from a vigorous root system. Fire and cutting encourage more growth, although those are also the two best control mechanisms short of chemicals.

Names: The genus Rhus, is derived from the old Greek name for Sumac - rhous. The species name, glabra, is Latin for "smooth". The author name for the plant classification, 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.

Comparisons: There are three sumacs in the Garden - Compare: Staghorn Sumac, whose twigs have dense fine hair, but no spots - and Fragrant Sumac which has much different leaves and flower clusters.