Ladysthumb (Polygonum persicaria), Polygonaceae

Ladysthumb description

Roots are fibrous. Stems are smooth, sometimes hairy, simple to much branched. Stems either ascend or lay flat and can reach 1 to 3 ft in height. Leaves are alternate, narrowly to broadly flattened, pointed at the tip and base. Leaves are thin, taper to both ends, and have two rows of parallel veins.

Propagation

Annual. Seed.

Similar species

Pennsylvania Smartweed, swamp smartweed, pale smartweed. Ladysthumb can be distinguished from other smartweeds by the long hairs on the upper edges of the sheaths, and by the absence of white matted hair or yellow glands on undersides of leaves. The leaf spots are not reliable for identification.

Distribution

Found across most of the United States.

Identifying Ladysthumb

Seedling

Cotyledons elliptical with red undersides. First true leaves are alternate, narrow, hairy on the upper surfaces and taper to both ends.

Mature plant

Erect, branched, 8 to 36 inches high at maturity. Stems smooth, but with distinct nodes at leaf axils. Each node has a membranous sheath, which is hairy and has long hairs on its upper edges. Stems green to red.

Leaves alternate, narrowly elliptic, 1 to 6 inches long, with smooth edges. Green above, lighter below, usually with a red to purple to black blotch in the middle of each leaf. Base narrows into stalk.

Root structure description

Taproot.