Like its common names suggest,
Smilax rotundifolia is a green vine with thorns. It is a crawling vine that can tangle itself within other plants and climb with small tendrils. The plant can grow up to 20 feet long by climbing objects and vegetation. If there is nothing for it to climb upon it will grow along the ground. It has woody stems that are pale green in color and are glabrous, the youngest of which are often square-shaped. As the vine dies, the stem turns from green to a dark brown color. Along the stem there are often black-tipped thorns that are about 1/3-inch-long. Some stems of Common green brier do not have thorns. The upper surfaces of the leaves are darker than the undersides. The rounded alternate leaves are about 2 to 5 inches long. The leaves are glabrous and never glaucous. There are 3 to 5 primary veins per leaf. Along the lower surfaces of the primary veins it is possible to find small prickles but they are not always present. The petioles are a quarter to half an inch long, light green in color and glabrous. Small sheaths with terminal tendrils are present at the base of each petiole. Common greenbrier has greenish white flowers that form in umbels of 3–20 flowers. The peduncles upon which the umbels of flowers are borne originate from the axils of the leaves. Male and female flowers are produced on different plant, as this genus is
dioecious. Both male and female flowers are about the same size at a quarter inch long. The flowers bloom for about two weeks in late spring and early summer. After this blooming period the female flowers are replaced by a
berry containing up to three seeds. == Fire ecology ==