Polygonum persicaria - ladysthumb

Family: Polygonaceae
Wetland Indictor Status: FACW

General Species Description

A smooth to sparsely hairy annual herb. It is erect, and leafy-stemmed. Look for them just above ankle height.


Leaf stalks are short and thick, with alternate leaves, lance-shaped, with smooth margins and sheathing stipules. The most important identifying characteristic of this herb is a dark purple blotch in the center of the leaf, sometimes blended in well.


Flowers are pink with a little bit of green, and they are very small, 2-3.5mm long. Blooms from March through September.


Fruits are shiny and black, round to oval shaped, 2-2.5mm long.


Can be found in moist to wet disturbed areas, especially in cultivated wetlands with standing water.


Ladysthumb is common throughout North America, yet occurs most commonly west of the Cascades.

Similar Species

As long as you have found the dark purple blotch on the leaf, and can identify the flower, you have your ladysthumb.

Ecological Value

Foliage is edible and is used by wildlife.

Human Value

Ladysthumb can form thick mats in aquatic or semi aquatic habitats, so it is helpful for erosion control.


Cooke, Sarah. Field Guide to Common Wetland Plants of Western Washington, and Northwestern Oregon. Seattle Audubon Society, 1997.

This page was created by: Christina Norton, August 2000

Return to Northwest Oregon Wetland Plants Project