Cinnamon vine (Dioscorea polystachya)

Synonyms: Dioscorea oppositifolia

Common Names: Chinese yam, air potato, Japanese mountain vine, Korean yam, Chinese potato

Description:

Cinnamon vine (Dioscorea polystachya) is an invasive perennial vine from China and East Asia, introduced to the United States in the 1800s for food, medicine, and as an ornamental plant [1]. It escaped cultivation by the mid-1990s and has since spread across much of the eastern and central United States, including Michigan [2]. MISIN tracks this species as a Watch List invasive that can form dense masses of vines capable of smothering native vegetation and threatening natural areas.

Habit:

Cinnamon vine is a slender, twisting vine that spirals counterclockwise as it climbs fences, shrubs, and trees, reaching up to 16 feet in height when supported [1]. The leaves are heart-shaped to fiddle-shaped ? often with three shallow lobes ? and range from about 3 to 6 inches long, with 7 to 9 prominent veins radiating from the base. Leaf arrangement shifts from alternate near the base of the vine to opposite higher up. One of the most distinctive features is the color: leaf margins, petioles, and new stems often carry a purplish-red tint, and emerging leaves may show a bronze hue [2]. From late June through September, look for the small, warty bulbils (aerial tubers) tucked in the leaf axils ? they look like very small potatoes and are the plant's main way of reproducing in North America [3]. Small, whitish-yellow flower spikes bloom from mid to late summer and smell faintly of cinnamon, which is where the common name comes from [1].

At-a-glance cues:

1. Vines spiral counterclockwise; native wild yam spirals clockwise
2. Small, warty, potato-like bulbils in leaf axils from June through September [1]
3. Purplish-red tint on leaf margins, petioles, and young stems [2]
4. Summer flowers smell faintly of cinnamon [1]

Leaves:

1. Arrangement: alternate in lower nodes, often opposite in upper nodes, occasionally whorled in threes [1]
2. Shape: ovate to heart-shaped, frequently three-lobed (fiddle-shaped) toward the upper stem [2]
3. Size: approximately 3?6 inches (7?15 cm) long, 3?4 inches wide [1]
4. Venation: 7?9 prominent veins radiating from the cordate base [2]
5. Margins: smooth, often tinged purplish-red, with an acuminate (pointed) tip [2]
6. Surface: glossy green above; emerging leaves sometimes bronze-tinged [2]
7. Petiole: long-stalked, purplish-red, base not clasping the stem [1]

Stems:

1. Habit: herbaceous, twining vine; dies back to the ground each winter [1]
2. Twining direction: counterclockwise (left to right)
3. Texture: smooth, thin, and wiry [1]
4. Color: greenish with a purplish-red tint on young stems [2]
5. Cross-section: rounded [1]
6. Underground: deep, persistent, elongated tuber up to 1 meter long that resprouts each spring [2]

Flowers:

1. Color: small, white to greenish-yellow [1]
2. Arrangement: arise from leaf axils in spike or paniculate (branched) clusters [2]
3. Fragrance: faint cinnamon scent [1]
4. Bloom time: mid to late summer (approximately July?August) [1]
5. Sex: dioecious ? male and female flowers on separate plants; seed production has not been observed in North America [3]

Fruit and seeds:

1. Fruit type: three-angled membranous capsule with winged seeds; rarely produced in North America [3]
2. Bulbils (aerial tubers): the primary reproductive structure in North America; small, rounded, warty, and potato-like; borne in leaf axils [3]
3. Bulbil color: tan to brownish; typically 0.5?1 inch in diameter [1]
4. Bulbil season: present from June through September; drop to the ground and overwinter before sprouting the following spring [3]
5. Dispersal: primarily by gravity; also carried by moving water downstream and by rodents [3]

Habitat:

Cinnamon vine is native to a broad belt from central and southern China through the Kuril Islands and Taiwan, where it grows in temperate forests and disturbed edges [4]. In the United States it has spread across much of the East, from Louisiana north to Vermont, and is now detected in several Michigan counties. It tolerates a wide range of light levels, from full sun to deep shade, but does best at intermediate light along forest edges and open canopy gaps [2].

The plant is most aggressive in rich, moist bottomland forests, along stream banks, roadside ditches, and fence rows ? wherever soils are fertile and disturbance has occurred [2]. It thrives particularly in silty loam soils that are high in nitrogen and in riparian (streamside) corridors, where flowing water can carry its bulbils to new sites [3]. It also tolerates drier, disturbed upland habitats and has been found near old home sites, roadsides, and waste areas [1].

Reproduction:

Seed production has not been documented in North America; cinnamon vine spreads here almost entirely through its bulbils ? the small, potato-like aerial tubers that form in the leaf axils between June and September [3]. A single vine can produce an average of about 20 bulbils per season, and even a partially chewed or broken bulbil can still sprout into a new plant [2]. Bulbils drop from the vine in fall, overwinter on or in the soil, then produce roots in early spring after cold temperatures have broken their dormancy ? typically not sprouting until temperatures warm above roughly 68 ?F (20 ?C) in March or April [3]. The underground tuber resprouts from the same point each year and grows deeper over time, making it very difficult to fully remove by hand.

Once on your property, bulbils can spread from a neighbor's yard or garden simply by falling to the ground or rolling downslope. Along streams, flood events can carry them hundreds of meters downstream, seeding new populations far from the original plant [3]. Rodents also gather and move bulbils, particularly from ornamental plantings near natural areas. The underground tuber can survive and resprout even if the vine is cut or mowed ? repeated removal over multiple seasons is required to exhaust the root reserves.

Impact and Damage:

Handling the raw tuber can cause skin irritation, and eating uncooked tubers may produce burning of the mouth, lips, tongue, and throat [1]. Gardeners who plant or move this species without knowing it is invasive are a primary pathway for new infestations ? bulbils are visually attractive and easily mistaken for a curiosity rather than a hazard [2].

In natural areas, cinnamon vine can form dense mats of vines that blanket native vegetation and block sunlight to the plants underneath, reducing native plant diversity and abundance [2]. Established infestations have been documented at up to 3 acres and can engulf shrubs and even the lower canopy of trees, weighting down and breaking branches in a manner similar to kudzu [2]. The plant exploits elevated soil nitrogen and outcompetes native ground cover almost entirely once established [2]. Great Smoky Mountains National Park has documented rapidly expanding populations across the Tennessee Valley, where cinnamon vine is establishing alongside other aggressive invaders [5].

Similar species:

Field bindweed (Convolvulus arvensis) is a spreading vine that can form large mats in disturbed areas, which makes it easy to mix up with cinnamon vine. Field bindweed is distinguished by its funnel-shaped white to pink flowers, each 1?2 inches across and lasting only a day. Its leaves are arrowhead-shaped, 1?2 inches long, with smooth edges ? much smaller than cinnamon vine's lobed heart-shaped leaves. It never produces potato-like bulbils in its leaf axils.

Wild yam (Dioscorea villosa) is the native look-alike most likely to cause confusion because both are heart-leaved twining vines that grow in similar moist, shaded habitats. Wild yam leaves share the same palmately parallel veins as cinnamon vine but are strongly heart-shaped (not three-lobed or fiddle-shaped) and have short hairs on their lower surface. Wild yam grows from a rhizome rather than a tuber and never produces aerial bulbils in its leaf axils ? that single feature is the quickest separation.

Buckwheat (Fagopyrum esculentum) has similar arrowhead-shaped leaves but is not a twining vine. Its leaf veins are pinnately arranged (branching from a central midrib), unlike the palmate venation of cinnamon vine. Its small white flowers are held in branched clusters with five petals, and it produces no aerial tubers.

Fringed black bindweed (Fallopia cilinode), a native vine, has arrowhead-shaped leaves with somewhat rounded basal lobes and pinnate venation. The easiest field mark is the ring of reflexed bristles at each stem node, which cinnamon vine lacks entirely. It produces no bulbils.

Monitoring and rapid response:

Signs to watch for:

1. From June through September, check vine-covered fences, shrubs, and forest edges for small, warty, potato-like bulbils tucked at the base of the leaf stems ? this is the easiest time to confirm identification [1]
2. Look for slender counterclockwise-twining vines with purplish-red stem and petiole color, especially along stream banks, fence rows, and disturbed wood edges
3. In late summer, sniff near white flower clusters ? a faint cinnamon scent confirms the species [1]
4. Even in winter, old dried vine canes clinging to shrubs and small trees can indicate a population; inspect these sites the following spring when new shoots emerge

What you can do:

1. For a small patch on your property, hand-pull young vines in spring or early summer before bulbils form, gripping as close to the soil surface as possible to remove as much tuber as you can
2. Cut vines repeatedly at the base throughout the growing season to exhaust the underground tuber ? a single cut is not enough, as the tuber resprouts; plan for multiple visits per season over at least two to three years
3. Collect and bag all bulbils before disposal ? do not compost them, as fragmented bulbils can still sprout; seal bags before placing in the trash [2]
4. For a natural area crew, prioritize small outlier populations first to contain the spread front, then work inward toward larger infestations; coordinated multi-visit mechanical removal across a site can reduce bulbil density significantly over time

When to call a professional:

1. If the infestation covers more than a small area or has established along a stream corridor, the underground tubers and water-dispersed bulbils make control very difficult without a multi-year management plan
2. Mature infestations that have re-sprouted repeatedly despite hand removal are strong candidates for professional management
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Michigan DNR / Michigan Invasive Species. Cinnamon Vine (Dioscorea polystachya). michigan.gov/invasives
2. IUCN Global Invasive Species Database. Dioscorea oppositifolia (accepted syn. D. polystachya). iucngisd.org
3. Walck JL, Cofer MS, Hidayati SN (2010). "Understanding the germination of bulbils from an ecological perspective: a case study on Chinese yam (Dioscorea polystachya)." Annals of Botany 106(6):945?955. semanticscholar.org (citation count could not be confirmed via Semantic Scholar ? see [verify])
4. POWO (Plants of the World Online). Dioscorea polystachya Turcz. Royal Botanic Gardens, Kew. powo.science.kew.org
5. Long Island Invasive Species Management Area (LIISMA). Cinnamon Vine (Dioscorea polystachya). liisma.org

---