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Western Wetland Flora

Field Office Guide to Plant Species

Lady's Thumb
Polygonum persicaria L.

JPG -- Species Photo JPG -- Distribution Map

Family: Smartweed (Polygonaceae)
Flowering: June-November
Field Marks: This species differs from similar smartweeds by its bristly sheaths, dense, erect spikes of pinkish flowers, and its annual habit.
Habitat: Moist, disturbed areas.
Habit: Annual herb with a taproot.
Stems: Upright or ascending, branched, up to 3 feet tall, usually smooth; sheaths bristly at the tip.
Leaves: Alternate, simple, lanceolate to linear-lanceolate, up to 5 inches long, up to 3/4 inch wide, pointed at the tip, tapering to the nearly sessile base, usually smooth.
Flowers: Many crowded in dense racemes, the racemes erect, up to 1 1/2 inches long, on smooth stalks.
Sepals: Usually 5, united below, usually pinkish, up to 1/6 inch long.
Petals: 0.
Stamens: 6-9.
Pistils: Ovary superior; styles usually 2.
Fruits: Achenes triangular or sometimes flattened, 1/8-1/6 inch long, smooth, shiny.
Notes: The distinctive blotch present on many of the leaves of the lady's thumb may also be present in other species of Polygonum. The achenes are eaten by waterfowl and small mammals.

Previous Species -- Willow-weed (Polygonum lapathifolium)
Return to Species List -- Group 8
Next Species -- Dotted Smartweed (Polygonum punctatum)

U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.npwrc.usgs.gov/resource/plants/florawe/species/8/polypers.htm
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Page Last Modified: Saturday, 02-Feb-2013 06:28:21 EST
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