Persicaria longiseta Bruijn) Kitag.

Common Name: Oriental lady's thumb

Synonyms and Other Names: Smartweed; Asiatic smartweed; Bristled knotweed; Bunchy knotweed; Long-bristled smartweed

Copyright Info

Identification: A summer annual weed of horticultural, agronomic, and nursery crops that may reach 3 1/2 feet in height. Seedlings: Cotyledons are elliptic to lanceolate in outline, whit hairs along the margins.  First true leaves are alternate, lanceolate in outline, and hairy on the upper surfaces. Roots:  Fibrous roots with a shallow taproot. Fruit:  A black achene. Leaves: Arranged alternately along the stem, lanceolate to elliptic in outline, approximately 3/4 to 3 inches long and 1/2 to 1 1/4 inches wide.  Older leaves are usually only slightly hairy.  Leaves taper to short petioles, which have an ocrea that encircles the stem.  Leaves often, but not always, have a purple spot in the middle of the leaf. Flowers:  Flowers are clustered in terminal spikes at the ends of stems.  Individual flowers are small and are dark pink to red in color.

The elliptic to lanceolate leaves with a purple spotted 'lady's thumb' print in the middle and distinctive ocrea with stiff hairs are all characteristics that help to distinguish tufted knotweed from other similar weeds. 

Size: 3.5 feet

Native Range: Native to Eastern Asia in China, Japan, India, Malaysia and Korea

Map Key
This map only depicts Great Lakes introductions.


Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Persicaria longiseta are found here.

State/ProvinceYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
Michigan197820082Great Lakes Region; St. Clair-Detroit
New York200820083Oneida; Oswego; Seneca
Ohio196020087Black-Rocky; Cuyahoga; Huron-Vermilion; Lake Erie; Sandusky; Southern Lake Erie; Western Lake Erie
Pennsylvania200820081Lake Erie

Table last updated 12/18/2020

† Populations may not be currently present.

Ecology: 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 (4.8 to 8). It can be found on ridge tops, open woods, trails, and roadsides near damp or wet places.

Means of Introduction: Unknown.

Status: Introduced – Naturalized

Great Lakes Impacts:

Remarks: Pennsylvania Smartweed (Polygonum pensylvanicum) is very similar in appearance and growth habit, but does not have hairs on the ocrea like that of tufted knotweed.  Ladys thumb (Polygonum persicaria) is also similar in appearance and growth habit, but has hairs on the ocrea that are much shorter (2 mm), and also has generally smaller leaves and dark pink to red flowers. 

Synonyms: Persicaria longiseta; Polygonum longisetum

References: (click for full references)

College of Agriculture and Life Science, Virginia Tech. 2008. Tufted Knotweed: Polygonum caespitosum var.longisetum.

Godfrey, R.K., Wooten, J.W. 1981. Aquatic and Wetland Plants of Southeastern United States: Dicotyledons. University of Georgia Press. 933 p.

USDA Forest Service. Invasive Plants website. 2008. Invasive Plants website: 

Other Resources:
Author: Cao, L.

Contributing Agencies:

Revision Date: 10/21/2008

Citation for this information:
Cao, L., 2023, Persicaria longiseta Bruijn) Kitag.: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI,, Revision Date: 10/21/2008, Access Date: 3/22/2023

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.