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 flowers are usually separate by sex and form in a compact, pyramid shaped 8 inch high cluster at the end of the branches. The small 5-parted flowers are greenish-yellow. The 5 stamens have yellow anthers.
Fruit will appear on plants 3 to 4 years old. Smooth Sumac and Staghorn are very similar in that the 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 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.
Above 1st photo - The green flower buds and 2nd photo - flower cluster of late May to Mid June. 3rd photo - The drupes formed in July with their red acid hair.
Below: Smooth Sumac can be trained and pruned to produce a nice shrubby plant cluster (1st photo)- full sun only though; native form shown in the 2nd photo. 3rd photo - A cluster of drupes in April that carried thru the winter.
1st photo Above and below: The characteristic leaf structure of Smooth Sumac. 2nd photo above - The smooth spring twig with new growth. Staghorn sumac would have hair on the twig and no spots. 3rd photo above and 2nd photo below show the smooth leaf stems and the spotted twigs.
Below: Each hairy drupe contains one ellipsoid shaped, slightly flattened, greenish-tan hard seed.
These galls affect both Staghorn Sumac (Rhus hirta) and Smooth Sumac (Rhus glabra). Some writers state they see them most often on Staghorn but in my area they are almost always on Smooth Sumac. This rather large gall arises when a small aphid, Melaphis rhois, lays an egg on the leaf underside. This causes the leaf to secrete material that forms a sac over the egg. Inside, a number of generations of aphids form and females leave the gall in late Summer where they lay eggs on a host plant and those eggs produce the aphids for the next seasons infestation.
John Muir wrote in 1911: Each species seems to know what kind of plant will respond to the irritation or stimulus of the puncture it makes and the eggs it lays, in forming a growth that not only answers for a nest and home but also provides food for the young." From his essay Mt. Hoffman and Lake Tenaya.
Below: 1st photo - a Smooth Sumac leaf with a number of galls. 2nd photo - Galls are large and frequently with reddish tints. 3rd photo - the inside of a gall with young aphids.
Notes: Smooth Sumac is indigenous to the Garden Area; Eloise Butler cataloged it on April 29, 1907. She planted two plants on May 15, 1914, obtained from her source in Boulder CO. It is native to all of North America from the lower Canadian Provinces down throughout the lower 48 states. In Minnesota it is found in most counties with the scattered exceptions being mostly in the western half of the state. It was listed on Martha Crone's 1951 Census of Garden plants and on all later census reports. The red berries can be used to make a drink along the likes of lemonade. The fruits have an agreeable, acidic taste when the mature fruit is washed briefly in water, then placing them in drinking water and crushing them with a spoon. Strain the liquid through a cloth to remove the hairs and seeds, add sugar to taste. The fine hairs contain the acid so they must be present in the crushing stage. The resulting beverage does not keep so make and use. (Ref. #9)
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"