Polygonum ramosissimum is an annual herb, to 1 m, freely branched, lower internodes to 5 cm long, becoming shorter upwards.
Leaves alternate, linear to narrowly lance-shaped, of two sizes, those of main stem to 6 cm long, 0.5 cm wide, becoming abruptly much smaller on branches; tip pointed to blunt.
Flowers green, with pinkish, or sometimes yellow, margins, 0.3 cm long, petals (tepals) 5, outer 3 longer than the inner 2; in clusters of 1-3 extending from upper leaf sheaths (ocreae).
Fruit dry, an achene enclosed in old flower parts, early in season shiny, black (Stalter and Tang 2002) 0.3 cm, longer than petals, later in season to 0.5 cm, often paler; blooming and fruiting July-Oct. (Hough 1983).
Wetland status: FAC.
Frequency in NYC: Very infrequent.
Habitat: Salt marshes or disturbed habitats in sandy moist soil.