Description: Procumbent or erect herbs, much branched, with woody taproot.
Leaves subsessile, base attenuate, with a band of abscission tissue at base; nectaries absent; ocrea lacerate, often nearly to base, silvery or whitish hyaline, tubular only at the very base.
Flowers bisexual, short-pedicellate to subsessile, solitary or in small clusters, forming axillary clusters or very lax leafy spikes. Perianth segments usually 5, subequal, not winged or keeled, sepaloid but pink or white towards the margins, not enlarged in fruit. Stamens 5–8; anthers versatile. Style usually trifid, very short; stigmas capitate, smooth.
Achene trigonous or rarely lenticular, enclosed in persistent perianth.
Distribution and occurrence: World: c. 50 species, cosmopolitan. Australia: 5 species, all States.
This genus has often been taken in a wide sense to include Fallopia, Persicaria, Reynoutria and other genera.
Text by K. L. Wilson
Taxon concept:
| | Key to the species | |
| 1 | Erect herb, stems not rooting at the nodes; flowering region more or less obvious because of the very small bract-like leaves; lower leaves mostly not persistent after flowering | Polygonum bellardii |
| Prostrate to decumbent herbs, commonly mat-forming, stems often rooting at the nodes; flowering region not obvious, leaves all similar or somewhat smaller in the flowering region but not bract-like; leaves usually persistent | 2 |
| 2 | Leaves narrow-elliptic to narrow-ovate, 5–50 mm long, 2–15 mm wide, with lateral veins visible on lower surface, margins flat, wavy or rarely recurved; stems to 100 cm long | 3 |
| Leaves linear-oblong to very narrow-elliptic, 3–20 mm long, 1–3.5 mm wide, lateral veins not visible, margins mostly strongly recurved (flatter on large leaves); stems to c. 15 cm long
Back to 1 | Polygonum plebeium |
| 3 | Branch leaves about half the size of stem leaves; perianth divided for about two-thirds its length, tapering abruptly below nut; nut with 3 subequal concave faces | Polygonum aviculare |
| All leaves of similar size; perianth divided for about half its length, tapering gradually to base; nut with 2 more or less convex faces and 1 narrower concave face
Back to 2 | Polygonum arenastrum |
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