Rough potato is a twining vine in the milkweed group from East Asia that bleeds white sap when broken. In summer it bears small, pale purple, star-shaped flowers with fuzzy centers, followed by warty pods that release silky-haired seeds. In the U.S. it has turned up only rarely, and Minnesota officials are working to contain it.
Appearance
- Growth form
- A perennial vine that spreads by underground stems. Stems twine up to about 6–10 ft (2–3 m) and can smother nearby plants.
- Leaves
- Opposite, long-stalked, heart-shaped leaves 2–4 in (5–10 cm) long, dark green above and whitish beneath.
- Flowers
- Clusters of 10–20 flowers grow from the leaf joints. Each is about 3/8 in (1 cm) across, pale purple to white, with five pointed lobes and a dense coat of white hairs inside.
- Flowering time
- Summer (July–August in its native range).
- Fruit
- A spindle-shaped pod 3–4 in (8–10 cm) long with a bumpy surface. It splits open along one side when ripe.
Look-alikes
Honeyvine milkweed (sandvine)Cynanchum laeve
Honeyvine milkweed has white, vase-shaped flowers in small clusters. Rough potato's flowers open flat into pale purple stars with hairy centers, and its pods are noticeably warty.
Why they get mixed upBoth are twining vines with opposite heart-shaped leaves, milky sap, and milkweed-style pods.
Where it lives
- Typical habitats
- Grasslands
- Roadsides
- Thickets
- Riverbanks
- Forest edges
- Range
- Native to Japan, Korea, China, and the Kuril Islands. In the U.S. it has rarely been recorded; in 2020 a naturalist found it along the Lake Wobegon Trail in Stearns County, Minnesota, and the county began mapping the patches.
- Preferred conditions
- Prefers sunny, open ground with well-drained, fertile soil, where it climbs over other plants and spreads into patches.
Life cycle
- Seed dispersal
- Flat brown seeds with long, silky white hairs drift on the wind, like other milkweeds.
Growing it
- Propagation
- Spreads both by seed and by creeping underground stems, which makes it hard to remove once established.
- Toxicity
- The underground stems are reported to contain toxic compounds.
Name and classification
- About the name
- Long known as Metaplexis japonica; recent classification moves it into Cynanchum as Cynanchum rostellatum.
Conservation
- IUCN Red List
- NENot EvaluatedNot yet assessed
- Threats
- An aggressive climber that can cover other plants. Minnesota officials advise cleaning gear, pets, and clothing before leaving an infested site, since seeds and plant pieces can hitch a ride.
More species to explore
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