Polygonum caespitosum, Oriental Ladysthumb

Gardens & Landscapes, Invasive Species, Extension Master Gardener November 10, 2012 Print Friendly and PDF

Invasive Species: Polygonum caespitosum, Oriental Ladysthumb

Oriental ladysthumb is an invasive annual forb that can reach 6 to 30 in. (15.2 to 76.2 cm) in height and can be either erect or sprawling. Leaves are elongate, narrow, and pointed at the base and tip. Stems have swollen nodes with papery sheaths (ocrea). Ocrea have long, hair-like bristles on the margin. Flowering occurs from June to October, when pink flowers develop at the apex of the stems. Flowers are 1/8 in. (0.3 cm) long and occur in groups. The fruit is a trigonous black achene. Oriental ladysthumb is native to Asia and occurs in disturbed habitats such as along roadsides and in pastures. Plants also inhabit wet areas.

What are invasive species and why should we be concerned about them? 


Taxonomy: Scientific and Common Names for This Species

Polygonales > Polygonaceae > Polygonum caespitosum Blume

Synonym(s): Persicaria longiseta, Asiatic smartweed, bristled knotweed, bunchy knotweed

Polygonum caespitosum - USDA PLANTS Profile

Distribution Maps

Oriental ladysthumb - The reported distribution of this invasive species across the United States (Source: Invasive Plant Atlas of the United States)

Up-to-the-minute distribution maps and why they are important 

Reporting This Invasive Species

What is the best way and place to report the occurrence of an invasive species? 

 How to report an invasive species sighting to EDDMapS - Early Detection & Distribution Mapping System

EDDMapS - Report an invasive species to EDDMapS.

Cooperative Extension Offices - Find your local Cooperative Extension office on this map provided by USDA.

How to Identify

This invasive species can be identified by looking for the characteristics described in the paragraphs that follow.

Plant

Oriental ladysthumb is an annual forb that can reach 6 to 30 in. (15.2 to 76.2 cm) in height and can be either erect or sprawling.

Leslie J. Mehrhoff, University of Connecticut, bugwood.org Leslie J. Mehrhoff, University of Connecticut, bugwood.org

Foliage

Leaves are elongate, narrow, and pointed at the base and tip. Stems have swollen nodes with papery sheaths (ocrea). Ocrea have long, hair-like bristles on the margin.

Leslie J. Mehrhoff, University of Connecticut, bugwood.org Chris Evans, River to River CWMA, bugwood.org

Flower

Flowering occurs from June to October, when pink flowers develop at the apex of the stems. Flowers are 1/8 in. (0.3 cm) long and occur in groups.

Leslie J. Mehrhoff, University of Connecticut, bugwood.org Leslie J. Mehrhoff, University of Connecticut, bugwood.org

Fruit

The fruit is a trigonous black achene.

   
bugwood.org bugwood.org

Native Species That Can Resemble Oriental Ladysthumb

Persicaria hydropiperoides, swamp smartweed - Bugwood.org

Ohio State Weed Lab Archive, The Ohio State University, bugwood.org Joseph M. DiTomaso, University of California - Davis, bugwood.org

Polygonum pensylvanicum , Pennsylvania smartweed - Bugwood.org

Dan Tenaglia, Missouriplants.com, bugwood.org Dan Tenaglia, Missouriplants.com, bugwood.org

Additional Images for Oriental Ladysthumb

Oriental ladysthumb - Images at Invasive.org

Learning Resources for Oriental Ladysthumb

Additional Information, Biology, Control and Management Resources

Control and management recommendations vary according to individual circumstances. Location, habitat, weather, and a variety of other conditions are factors that help determine the best treatment choice. To find the safest and most effective treatment for your situation, consult your state's land-grant institution. If you will use chemicals as part of the control process, always refer to the product label.

United States Land-Grant University System - Find your land-grant university's college of agriculture, Cooperative Extension office, or other related partner on this map provided by USDA.

Fire Effects Information System - US Forest Service

Invasive Plant Atlas of New England - University of Connecticut

Weed of the Week - US Forest Service


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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.