Mile-a-minute Weed (Persicaria perfoliata) — identification, habitat & look-alikes

Mile-a-minute weed is a fast-growing, barbed annual vine from East Asia that has become a serious invader in the eastern United States, where a single vine can cover up to 30 ft (9 m) in one season and smother shrubs and young trees. It has triangular leaves, round saucer-like collars around the stem, and clusters of metallic-blue berries. It is also called devil's tail or Asiatic tearthumb.

Appearance

Growth form: A trailing annual vine that climbs over other plants using small backward-pointing barbs on its stems, leaf stalks, and the undersides of its leaves.
Leaves: Light green, triangular leaves about 1 in (2.5 cm) wide, alternating along thin, reddish stems. A round, saucer-shaped sheath called an encircles the stem at each leaf.
Flowers: Small, pale green, and easy to overlook.
Fruit: Berry-like clusters about 1/4 in (6 mm) across turn from green to purple to metallic blue. Each segment holds one shiny black seed.

Look-alikes

arrowleaf tearthumbPersicaria sagittata

Arrowleaf tearthumb has narrow, arrow-shaped leaves and no round saucer (ocrea) around the stem. Mile-a-minute has broad triangular leaves with a large, obvious saucer at each leaf.

Why they get mixed upThis native vine also has backward-pointing barbs on its stems.

halberd-leaved tearthumbPersicaria arifolia

Its leaves are shaped like a medieval halberd, with flaring lobes at the base, and it has no saucer-shaped ocrea. Barbs plus a saucer mean mile-a-minute.

Why they get mixed upAnother native barbed vine with roughly triangular leaves.

hedge bindweedCalystegia sepium

Hedge bindweed has smooth stems with no barbs and no saucer around the stem, and its triangular leaves have a notched, concave base.

Why they get mixed upIts triangular leaves on a climbing vine look similar at a glance.

Where it lives

Typical habitats: Forest edges
Stream banks
Wetlands
Roadsides and ditches
Fields
Range: Native to East Asia, India, and the Philippines. In the US it is found mainly in the Northeast and Mid-Atlantic states, where it is still spreading; it occupies only an estimated 20% of its potential US range.
Preferred conditions: Prefers open, sunny, fairly moist sites, but tolerates partial shade.
Seasons: In Virginia
Fruit Jun–Oct

Behavior

Activity: In the eastern US, seeds sprout in early April. Flowers and fruit appear from early summer (as early as June in Virginia) until the first frost kills the plants.

Life cycle

Seed dispersal: Birds are the main long-distance carriers; deer, chipmunks, and squirrels also eat the fruit. Ants move seeds short distances, and fruit can float for 7–9 days, so it spreads along streams. Seeds stay alive in the soil for at least six years.

Conservation

IUCN Red List: NENot EvaluatedNot yet assessed
Status: It is managed as an invasive plant in the eastern US. To remove small patches, wear leather gloves and long sleeves, pull plants before seeds form, and never compost the fruit or seeds.
Threats: It smothers native plants and reduces plant diversity. A tiny weevil that feeds only on this plant, the mile-a-minute weevil (Rhinoncomimus latipes), was approved for release in 2004 and has since been released in the eastern US as biological control.

Culture and stories

Culture and stories: It reached the US by accident several times between the late 1800s and the 1930s. The population that took hold began at a Pennsylvania plant nursery, sometime between the late 1930s and 1946.