Dioscorea quaternata J.F. Gmel.

Wild Yam

© DETenaglia

Family - Dioscoreaceae

Habit - Rhizomatous perennial forb, dioecious. Rhizomes 10-15 mm in diameter when fresh, usually contorted and knobby.

Stems - Twining and climbing on other vegetation, to 5 m, usually round in cross section and without ridges, glabrous.

	Stem and whorled leaf node.
© SRTurner

Leaves - Lower leaves in whorls of 4-9, petiolate, the upper leaves whorled or alternate. Petioles to 6 cm long, glabrous, with a swollen pulvinus at the base. Blades 4-26 cm long, heart-shaped, the base cordate, the tip acuminate, the margins entire, the main veins 9-11 veins, these palmately arched from the leaf blade base and converging toward the tip, the smaller veins branched and forming a network between the main veins, glabrous or hairy, shiny to dull green.

	Leaves.
© SRTurner

	Leaf adaxial.
© SRTurner

	Leaf abaxial.
© SRTurner

	Leaf abaxial surface.
© SRTurner

Inflorescence - Staminate inflorescences axillary panicles to 10 cm long. Pistillate inflorescences axillary spikes.

	Staminate inflorescences.
© DETenaglia

	Staminate inflorescence.
© SRTurner

	Pistillate inflorescence.
© SRTurner

Flowers - Staminate flowers with 6 light yellow tepals 1-2 mm long and 6 stamens. Pistillate flowers with 6 light yellow tepals 1-2 mm long, 6 vestigial, nonfunctional stamens, and 1 inferior ovary 4-7 mm long with 3 locules. Styles 3 per flower, branched at the tip into 6 stigmas.

	Staminate flowers.
© SRTurner

	Pistillate flower.
© SRTurner

	Pistillate flower, lateral view.
© SRTurner

Fruits - Capsules, 3-winged, circular to broadly ellipsoid in outline. Seeds usually 2 per locule, flat, broadly winged.

	Fruits.
© DETenaglia

Flowering - April - June.

Habitat - Mesic bottomland and upland forests, frequently on mesic, rocky slopes, thickets along creeks.

Origin - Native to the U.S.

Other info. - This species is very similar to the closely related D. villosa, and distinguishing the two can be very difficult. Many botanists believe that they are the same species. Characters which may point to D. quaternata include a round (not angled) aerial stem, whorls of at least four leaves per node near the base, and robust rhizomes (10-15mm diameter) which are contorted and knobby. Although some specimens may show intermediate characters, others are fairly distinct and conform well to the concept described here. The species can be found in the southeastern quadrant of Missouri. Wild yams found elsewhere in the state are probably D. villosa.

Photographs taken in Linville, NC., 5-11-03, and at Big Spring Park, MO., 7-8-04 (DETenaglia); also at Holly Ridge Conservation Area, Stoddard County, MO, 5-23-2022 (SRTurner).