Polygonum tenue is an annual herb, 10-40 cm tall, very slender, with numerous sprawling or ascending branches, nodes swollen (UW-Stevens Point, Freckmann Herbarium 2009).
Leaves alternate, linear, to 3 cm long, pointed at both ends, spine-tipped, margin minutely spine-toothed, folded lengthwise along each side of the midrib, leaves of branches reduced to floral bracts.
Flowers white, sparse, mostly one at each axil growing from leaf sheath, petal lobes covering developing seed; fruiting flower 0.3 cm long; blooming July to Sept..
Fruit dry, 0.3 cm long, petals becoming pale to slightly pink, tightly covering dark brown or black seed; fruiting Aug-Oct. (Hough 1983).
Wetland status: UPL.
Frequency in NYC: Very infrequent.
Habitat: Dry open, acid soil.