Eastern Forest Threat Center - Oriental Ladysthumb

Search Again

State Information

Select a state,
then click a link.

  • State Forest Agency
  • State Cooperative Extension

County/Parish Information

Select a county,
then click a link.


Oriental ladysthumb flowers

Oriental ladysthumb flowers

Leslie Mehrhoff, University of Connecticut, Bugwood.org

Oriental Ladysthumb
Polygonum caespitosum

Oriental ladysthumb is native to China, Japan, Korea, India, and Malaysia.

Keywords: Polygonaceae, herbaceous, annual, reddish stems; Common names: Asiatic smartweed, bristled knotweed, bunchy knotweed, long-bristled smartweed

Distribution Map Distribution Source Image

Threat Description

Oriental ladysthumb is an herbaceous annual in the buckwheat family reaching about 3 ft. in height. The stems can be erect or prostrate, and are freely branched, reddish in color, and swollen at the nodes. The thin, dark green, alternately arranged leaves are lanceolate to elliptic in shape and measure ¾-3 in. long and ½-1 ¼ in. wide. The leaves are mostly glabrous, but the older leaves can sometimes have hairs on the margins and veins on the lower leaf surface. Flowers are clustered in terminal spikes at the ends of stems. Individual flowers appearing from July to October are small and dark pink to red in color. The black, smooth, shiny achenes are dispersed mechanically. Roots are fibrous with a shallow taproot. Oriental ladysthumb grows in moist soil and can grow in low light situations. It is often found in poor soils and can tolerate a wide range of pH. It can be found on ridge tops, open woods, trails, and roadsides near damp or wet places. It has the potential to invade shaded natural areas and out-compete other native species that thrive in moist, shaded habitats.