Willow weed is a plant species that is variable in appearance and may be both native and introduced. "Persicaria lapathifolia is a morphologically variable complex with more than two-dozen infraspecific taxa described in the New World and Old World." (Hinst and Freeman 2012).

General:
Annual herb from a taproot; stems erect (occasionally prostrate), solitary, usually freely branched, 20-80 cm tall/long.

Leaves:
Basal leaves lacking; stem leaves alternate, lanceolate or oblong-lanceolate, smooth or more often hairy or glandular below, the blades 5-20 cm long, the stalks short; stipules 5-20 mm long, brownish, more or less smooth, fringed with bristly hairs at the top.

Flowers:
Inflorescence a loose, often drooping panicle of spikelike racemes, 1-6 cm long; perianths greenish-white to pink, distinctly veined, the veins branching and turned back at the tip, about 2.5 mm long, 4- to 5-lobed nearly to the base.

Fruits:
Achenes, usually lens-shaped, egg-shaped to nearly rounded, dark brown, smooth and shiny, 2-3 mm long.

Source:  The Illustrated Flora of British Columbia

If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.

Illustration Source:  The Illustrated Flora of British Columbia

Synonyms and Alternate Names:
Polygonum lapathifolium L.
Polygonum scabrum