Polygonum plebeium R.Br.
small knotweed
Prostrate, nearly glabrous, mat-forming herb; taproot present; stems usually < 15 cm long, with angles minutely puberulent. Lvs all similar, sessile. Lamina 3-9 × 0.5-1.5 mm, linear or slightly spathulate, granular-punctate, entire; lateral veins not evident but midrib conspicuous; base attenuate; apex obtuse or subacute. Ochreae to c. 3 mm long, silvery-hyaline, soon lacerate with aristate points, often enclosing nearly 1/2 the internode. Fls axillary, in fascicles of 1-5; pedicels to c. 0.5 mm long at anthesis, usually enclosed by ochreae. Perianth c. 1 mm long at anthesis, pinkish, accrescent; segments imbricate, oblong. Nut 1.2-1.7 mm long, ovoid, dark brown or black, smooth, glossy, triquetrous with ridges obtusely angled.
N.: rare, scattered localities from Great Barrier Id to Wellington Province (Ruamahanga R.), most recently collected in 1946 from around Lake Waikaremoana.
Africa, tropical Asia, Australia 1853
FL Nov-Mar.
P. plebeium was first recorded by Hooker (1853, as P. dryandri Sprengel). The status of this plant in N.Z. is uncertain; Cheeseman (1925) stated that it was abundant in both main islands and accepted it as indigenous. However, Allan (1940) listed it as a naturalised sp. and stated that it had often been confused with the P. aviculare complex. Allan's assessment is probably correct, but it remains a possibility that P. plebeium is indigenous. In E. Australia, it is likewise apparently rare and localised and is always considered to be indigenous.
