Davis's knotweed

Polygonum davisiae W. H. Brewer ex A. Gray, Proc. Amer. Acad. Arts 8: 399. 1872; Aconogonon newberryi (Small) Soják; P. newberryi Small

Plants 12-42(-50) cm. Stems ascending to erect, glabrous or pubescent. Leaves: ocrea reddish brown, funnelform, 0.3-3 cm, margins oblique, glabrous or finely pubescent to pilose; petiole 0.3-10(-15) mm; blade oblong-ovate to ovate, rarely broadly lanceolate, 2.1-7.5(-9.5) × 1.1-5 cm, subcoriaceous, base truncate or, rarely, cordate, margins entire, glabrous or ciliate, apex obtuse to acute, faces often glaucous, glabrous or pubescent. Inflorescences axillary, racemelike; peduncle essentially absent. Pedicels 0.5-1.9(-2.4) mm. Flowers 1-4 per ocreate fascicle, rarely some flowers with stamens poorly developed; perianth greenish to pinkish white, 2-4.5 mm; tepals slightly dimorphic or, rarely, distinctly so, oblong-ovate to obovate, apex obtuse; anthers yellow or pink. Achenes exserted, yellowish brown, not beaked distally, 3.2-6(-8.3) × 2.1-5 mm, shiny, faces not concave. 2n = 20.

Varieties 2 (2 in the flora): w United States.

The varieties are largely sympatric and often intergrade. The treatment here follows Hong S. P. (1991).