Polygonum arenastrum door weed Polygonaceae POAR2*; Bx, br, cn, pb; NY, ct, rr, wr; Q f, ft, j, lk; K, fs, pl; R, fk, lc, lp;

 

Polygonum arenastrum

Polygonum arenastrum.Aldo De Bastiani.Luirig.altervista.org. (Accessed 4/2014).

Polygonum arenastrum is an annual herb, to 10 cm tall, taprooted, freely branched, sprawling to reclining, mat-forming; stipules (ocreae) sheath-like, membranous, 2-parted, becoming  ragged. 

Leaves alternate, stalk short, jointed at juncture with basal sheath; blade 0.5-2 cm long, 0.3-0.9 cm wide cm, elliptic, dark bluish-green, often deciduous late in season, leaves. 

Flowers green with white or pink margins, 1-5 in axils, tubular, petal lobes 5, to about as long as tube (corolla divided to middle), stamens 5, styles 3; mature flowers to 0.26 cm long; self-fertile (autogamous), apparently not visited by insects, (Mulligan and Kevan 1973); blooming and fruiting June-Sept. sometimes to Dec. (Hough 1983). 

Credit: Photo by Aldo De Bastiani

Polygonum arenastrum.flower and leaf.photo credit: Aldo De Bastiani.luirig.altervista.org (Accessed 3/2016).

Fruit dry, an achene, 0.2 cm (to 0.4 cm late in season), 2 sides flat or convex, third side narrowly concave, dark brown, pitted and grooved, seeds eaten by birds (Mitchell and Dean 1978). Seeds eaten by mourning doves and other seed-eating birds (Yatskievych 2006). 

Wetland status: FACU. 

Frequency in NYC: Occasional (probably more common than indicated). 

Origin: Eurasia. 

Habitat: Open, disturbed areas. More common in ball fields, curbs, roadsides, lawns. 

Note: Much like P. aviculare but leaves and achenes smaller and without large, early season leaves). Polygonum buxiforme, a rare native plant, is very similar but found in sand dunes and coastal sandy soil.