This is a herbaceous vine about 5-30' long that branches occasionally.
Its slender stems have the capacity to twine around adjacent vegetation
and fences, climbing upward and outward. The glabrous stems are light
green, pale yellow, reddish green, or dark red. The stems are usually
terete; less often, they are bluntly angular or narrowly ridged.
Whorled and/or opposite leaves sometimes occur near the base of the
vine, otherwise the leaves are alternate. At maturity, individual leaf
are 2-4" long and 1½-3" across; they are narrowly cordate to cordate,
smooth along their margins, and palmately veined (7-11 veins per leaf).
The upper blade surface is medium green and glabrous, while the
lower surface is pale green and sparsely short-pubescent (less often,
glabrous or densely short-pubescent). Very young leaf blades are golden
green in appearance. The slender petioles are 1½-6" long, light green
to dark red, and glabrous or nearly so; sometimes there are tufts of
hair where the petioles join the leaf blades. The leaf blades tend to
hang downward from their petioles.
Wild Yam is dioecious, producing
vines with either all male flowers or all female flowers. On male
vines, panicles of numerous male flowers about 4-12" long develop from
the leaf axils. Male flowers are arranged in small clusters of 1-3
along the branches of each panicle. Individual male flowers are about
1/8" (3 mm.) across, consisting of 6 whitish green or yellowish green
and 6 fertile stamens. On female vines, racemes of 5-15 female flowers
about 3-9" long develop from the leaf axils. Individual female
flowers are about 1/8" (3 mm.) across and 1/3" (8 mm.) long, consisting
of 6 whitish green or yellowish green tepals and a large inferior ovary
with 6 infertile stamens. The blooming period occurs during early
female flowers are replaced by 3-celled seed capsules that are ovoid in
shape and about 1" long; these capsules are strongly 3-angled and
become golden green as they mature. Each cell of the capsule usually
contains 2 seeds (less often, only 1). The flattened seeds have broad
membranous wings; they are distributed by the wind. The root system is
The preference is partial to full sun, moist to mesic
conditions, and soil consisting of loam or sandy loam.
This vine can survive in light shade, but it is less likely to produce
flowers and seed capsules. There are very few problems with insects and
The native Wild Yam is
occasional to locally common in Illinois; it is found in every county
Habitats include thinly wooded bluffs, typical
savannas and sandy savannas, woodland borders, typical thickets and
sandy thickets, moist sand prairies, powerline and railroad clearances
in wooded areas, and fence rows. Wild Yam is found in both high quality
and degraded habitats; it benefits from occasional wildfires and other
kinds of disturbance that reduce competition from overhead canopy trees.
There is very little information about
relationships for this species. The foliage appears to
as a food source by mammalian herbivores. Dense tangles of this vine
can enhance nesting habitat for birds and provide cover for various
The photograph of leaf blades
was taken along a fence row in Vermilion County, Illinois, while the
photographs of the seed capsules and flowers were taken in moist sandy
the Indiana Dunes National Lakeshore in NW Indiana.
somewhat similar Greenbriers and Carrion Flowers (Smilax spp.
Yam is a monocot, rather than a dicot. This vine is related to the
tropical Yam that is found in grocery stores, but it does not produce
edible tubers. Wild Yam can be readily distinguished from similar vines
by the palmate venation of its leaves, its racemes or panicles of tiny
flowers, and its conspicuous 3-angled seed capsules. In southern
Illinois, there is the very similar Dioscorea quaternata
Yam), which tends to have more whorled leaves than the common Wild Yam
that is described here. There is disagreement among authorities
regarding the taxonomic status of Whorled Wild Yam: While some
authorities regard it as a distinct species (e.g., Mohlenbrock, 2003),
other authorities consider it to be merely a variety of Wild Yam, and
still others think it is unworthy of any taxonomic recognition.