Wild yam is a native perennial vine that twines -- always counterclockwise -- up trees and shrubs to 5 m. It grows in open moist woods, along fence rows and marsh borders.
Origin of the name: Dioscorea, for Dioscorides, 1st century Greek physician who wrote about the botany and medicinal properties of hundreds of species; villosa, L. with long, soft hairs.
Range: MA to FL, w to MN, TX
WI Range: Statewide, except northernmost counties
Common associates: Hog peanut, hackberry, gray dogwood
Wetland Indicator Status: FAC-
Coefficient of Conservatism: C = 7 (S&W), C = 4 (MI)
Leaves are alternate and
heart-shaped with long pointed tips. Major veins originate from the base of the leaf and curve nearly parallel following the leaf shape.
Finer veins form a network between the major ones. On most plants the undersides of the leaves have soft hairs.
Wild yam is dioecious -- male and female flowers are on separate plants. Small,
white to greenish-yellow flowers form clusters in the axils of the leaves in June and July. The fruit is a 3-winged capsule with large and very flat, winged seeds. The capsules persist on the vines well
into the winter, even after the seeds are shed, so it’s easy to identify the female vines all year.
The yam family is mostly tropical and subtropical with D. villosa the only member of the family in Wisconsin. Some species of Dioscorea have edible tuberous roots, but wild yam does not. It has long tangled rhizomes, 5 to 10 mm thick, that have been used to treat colic. The orange-fleshed “yam” in the grocery store is actually a “sweet potato” (Ipomoea) in the Morning glory family.