Polygonum pensylvanicum L.
Family - Polygonaceae
Stems - To +80cm tall, herbaceous, erect to ascending, widely branching at or near base, mostly glabrous but glandular pubescent near inflorescence, from big taproot.
Portion of upper stem showing glandular pubescence.
Leaves - Alternate, petiolate, sheathing. Ocrea glabrous, NOT fringed. Petiole to 1.5cm long, glabrous. Blade typically lanceolate, acuminate, glabrous (or scabrous just on midrib), punctate below, entire, to 15cm long, +3cm wide, slightly decurrent on petiole. Margins antrorse strigillose.
Inflorescence - Terminal and axillary racemes to 4-5cm long, 1.5cm thick. Peduncles glandular pubescent. Ocreolae NOT fringed. Pedicels to 2.5mm long, glabrous.
Flowers - Perianth segments 5, 3mm long, 2.1mm broad, broadly elliptic, glabrous, whitish-pink to white. Stamens 10, mostly included to barely exserted. Filaments to -3mm long, glabrous. Anthers pale pink to pinkish-rose. Styles 2, joined for about half their length, free above, whitish, glabrous. Stigmas globose. Ovary green, glabrous, compressed, rotund, .9mm in diameter. Mature achene brown, slightly 3-sided, -3mm in diameter, shiny, glabrous, with concave sides.
Flowering - May - October.
Habitat - Moist to wet locations, gravel bars, disturbed sites, waste ground, roadsides, railroads.
Origin - Native to U.S.
Other info. - The perianth
of this species is variable between pink and white. Steyermark breaks the
species apart into 3 varieties and 3 forms depending on leaf and stem pubescence
and flower color. The plant described above is P. pensylvanicum
var. laevigatum f. laevigatum.
Photographs taken off Hwy 60, Carter County, MO., 8-31-03.