Roundleaf Greenbrier is a native woody climbing vine with tendrils. The stems, may be rounded or angled, have flattened sharp stout green spines that have blackened tips, but spines may be isolated to the lower stem parts of woody plants. Plants in colder zones may die back each year. The numerous tendrils emerge at the leaf stalk.
The leaves are alternate, simple, heart-shaped to rounded, with 3 or more prominent parallel veins (may be 5+ or -), reticulated between the veins, smooth margins, leathery in texture, glossy green above, matte green below; some plants may have leaf underside with minute fine hair. Leaves taper to an abrupt point. Smilax leaves are unusual in that they lack an abscission layer to separate the leaf at the end of the season. Instead the upper portion of the leaf stalk (the petiole) softens and disintegrates, allowing the leaf to fall off leaving a short stub.
The inflorescence is an umbel of 5 to 12 (20) 6-parted flowers with a yellowish-green perianth although it can shade to bronze on some plants. It may be open or dense, hemispherical to spherical in shape. The stalk of the umbel rises from the axil of an upper leaf. In that instance, there is no tendril at that stalk and the stalk of the inflorescence will be less than 1.5 times the length of the leaf stalk. If longer the species is probably different.
Flowers: Plants of the Smilax genus are unisexual, that is, male and female flowers are separate. The male flowers have 6 green to bronze tepals and six stamens. Tepals are 3 to 4 mm long. Anthers are shorter than, or equaling the length of the filaments. The female flowers have 6 green to bronze tepals and an ovary with a single 3-parted style. The tepals reflex exposing the round ovary. Female flowers may have 6 false stamens (staminodes) and male flowers may have a false pistil (a pistillode).
Seed: Fertile flowers produce a round 1/3 inch diameter berry, yellow green initially, turning blue-black at maturity, which contains 1 to 3 seeds that have a distinct ridge on one side.
Habitat: Roundleaf Greenbrier grows in the understory of moist woods and may be found in old fields with other pioneering species that occur in depleted soils. It can be invasive and is resistant to common herbicides such as glyphosate. The plant grows from long, slender rhizomes by which it regenerates, in addition to seed regeneration.
Names: The genus Smilax, is from the Greek, meaning 'clasping' as the tendrils indeed do. The species rotundifolia, is used to refer to species with rounded leaves. 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: In close resemblance to this species is Bristly Greenbrier, S. tamnoides, but there the leaves are more oval and the stems usually have bristly hair, but smooth angled stems are also known. Look also at the two Carrion Flowers, Smilax ecirrata, Upright Carrion Flower and Common Carrion Flower, S. lasioneura. Leaves and stems are somewhat similar, but not the flowers and seeds.
Above: Roundleaf Greenbrier is a climbing vine using tendrils and is found in the understory of moist woods. Drawing from Britton, N.L., and A. Brown. 1913. An Illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: Leaves are rounded with heart-shaped bases, 3 or more prominent veins, reticulated between the veins, and tapering to an abrupt point. The leaf stalk has a large stipule resembling a sheath.
Below: Two examples of female flowers showing the 6 tepals, ovary and 3-parted style. The tepals and perianth can vary from medium green to bronze. The umbel may be open to hemispherical to spherical.
Above and below: Tendrils rise from the leaf axis. The yellow-green berries turn to blue-black (below) at maturity and contain 1 to 3 seeds.
Below: The underside of the leaves is usually smooth but may have minute fine hair as shown here.
Notes: Roundleaf Greenbrier was reported planted by Eloise Butler in Oct. 1917 when she logged planting one root obtained from the prairie at Minnehaha, and another in 1918 from the same spot. Then in 1919 from the vicinity of the Lake Harriet Rose Gardens. However, considering that the University and the Minnesota DNR report no confirmed collection of the plant at anytime anywhere in Minnesota, this must be considered suspect and the plant was possibly a smooth angled stem version of the only Greenbrier mentioned in Eloise Butler's Garden Log from the early years - - Bristly Greenbrier, S. tamnoides, which is found in Minnesota and Hennepin County where Minnehaha is located. Flora of North America states that the two can be confused. Martha Crone mentions only S. tamnoides on her 1951 report and she noted planting "Roundleaf Greenbrier" in 1948. Roundleaf Greenbrier occurs mainly in the Eastern half of the U.S. east of the Mississippi (exc. for WI and VT). In Canada it is known only in Ontario and Nova Scotia. It is not considered native to Minnesota. The University notes that reports of its presence in SE Minnesota are probably misidentified specimens.
There are five species of Smilax found in Minnesota: S. ecirrhata, Upright Carrion-flower; S. herbacea, Smooth Carrion Flower; S. illinoensis, Illinois Greenbrier (or Illinois Carrion Flower); S. lasioneura, Blue Ridge Greenbrier (or Common Carrion Flower); and S. tamnoides, Bristly Greenbrier. S. pulverulenta, Downy Carrion-flower, has been reported but never collected. About 20 species are found in North America.
Uses: One use of the Greenbriers was to make jelly from the roots. This was done with both S. rotundifolia and S. glauca. The long slender roots of these plants, when exposed to air will oxidize to a reddish color. They were then powdered or cut into pieces and placed in cold water and boiled for an hour. This made the same colored water as you got by first powdering the root and then mixing the powder in water. In either case the colored water was strained, and it was boiled again with sugar and it jelled. Depending on the amount of sugar you either got a paste like a gumdrop or a soft jelly, slightly bitter-aromatic but intensely sweet. The jelly from S. rotundifolia would come out tea-colored. Mixed with water it made a sweet drink. Tender shoots also were used for a salad. (details in Fernald, Ref. 6).
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"