Smilax rotundifolia aka Common Greenbrier

Smilax rotundifolia is a woody vine called round-leaved greenbrier or bullbrier. It belongs to the greenbrier family, Smilacaceae. Its native range spans eastern Canada and central and eastern America. It grows in woods, fields, thickets, and along pond edges. Plants may lose their leaves or keep some through winter. Tendrils help the vine climb nearby plants or garden supports. Without support, it trails across the ground or forms tangled bushes.

Garden plants reach about 13–26 feet [4–8 metres] tall. RHS gives a spread of 8–13 feet [2.5–4 metres]. NC State reports wider plants, spreading to 20 feet [6.1 metres]. Stems are green, tough, and often four-sided, with stiff prickles. Some stems lack prickles, but handling still calls for care. Smooth, thin bark turns brown as stems age. Glossy leaves grow in an alternate pattern along the stems. Their bases are heart-shaped, and their undersides are paler. Each leaf has three to five main veins.

Small flowers grow in umbels during spring or summer. Their shades range from greenish white to yellow-green or bronze. Male and female flowers grow on separate plants. Both sexes must grow nearby for plants to produce seed. Round berries ripen in autumn and turn blue-black to black. A pale coating gives ripe fruit a dusty look. Each berry holds one to three seeds. Birds and mammals eat the fruit and leaves during colder months. Dense growth also shelters birds and small mammals.

Grow this vine in sun or partial shade with support. It suits well-drained soil that ranges from dry to moist. It tolerates clay, loam, sand, and rocky ground. RHS also lists acid, neutral, and alkaline soils as suitable. NC State gives USDA zones 4–9; RHS rates it H6. Growth is moderate, but maintenance can be high. Rhizomes help it spread, and it can become a troublesome weed. It suits wildlife gardens, screens, and thorny barriers. RHS reports few pest or disease problems. Its high fire risk makes it unsuitable close to homes.

Young shoots and leaves are edible raw or cooked. Cooked roots supply starch and can thicken food. Dried root powder has uses in cakes, puddings, and drinks. Records describe folk uses for leaves, stems, and prickles. These uses do not establish medical benefit. ASPCA lists it as non-toxic to cats, dogs, and horses. PFAF reports no known hazards, though prickles can cause injury.