Dioscorea polystachya
Chinese yam
Overview
Dioscorea polystachya is a herbaceous perennial vine in the yam family that twines counterclockwise and climbs 10–16 feet (3–5 m) in a single season from a deep underground tuber. The stems are slender, sometimes tinged purple, and die back to the ground each winter. The leaves are heart-shaped to halberd-shaped, 2–4 inches (5–10 cm) long, with deep basal lobes and prominent veins, arranged opposite or alternate along the stem. Small white to greenish flowers about 0.1 inch (2–3 mm) across hang in slender clusters from the leaf axils in summer and carry a faint cinnamon scent, though flowering is sparse on many plants. Most reproduction occurs from small aerial tubers, called bulbils, that form in the leaf axils and drop to grow new plants, and from the large starchy underground tuber that can reach 3 feet (1 m) deep. Dioscorea polystachya is native to East Asia and is grown for its edible tuber, but it has naturalized across the eastern and central United States, where it is listed as an invasive species in several states. It spreads rapidly along stream banks, fencerows, and forest edges, climbing over and shading out native vegetation.
Native Range
Native to China, Korea, and Japan, and cultivated widely in East Asia for its edible tuber. It has naturalized in the eastern and central United States, where it grows along streambanks, roadsides, fencerows, and disturbed woodland edges.Suggested Uses
Dioscorea polystachya is grown in parts of the world for its edible underground tuber and was once planted as a fast-growing screen vine. In the United States it is now managed as an invasive weed rather than planted, and removal is the typical goal where it occurs.How to Identify
Appearance
Size & Dimensions
Height10' - 16'
Width/Spread3' - 10'
Bloom Information
Small white to greenish flowers appear in summer, generally June to August, in slender drooping clusters from the leaf axils. The flowers carry a faint cinnamon scent but are often sparse or absent. Aerial bulbils develop in the leaf axils through late summer and autumn.
Detailed Descriptions
Flower Description
white to greenishFoliage Description
greenGrowing Conditions
Sun Requirements
Requires 4-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight