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Naturalized flora of The Morton Arboretum
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Polygonum plebeium
R. Br.
Family:
Polygonaceae
Common Knotweed
[
Polygonum changii
Kitag.,
more
Polygonum miquelianum
Meisn.,
Polygonum parviflorum
]
FNA
Resources
Mihai Costea, François J. Tardif, Harold R. Hinds+ in Flora of North America (vol. 5)
Plants
bluish green, homo-phyllous.
Stems
prostrate, much-branched from base, not wiry, 10-40 cm, papillose-scabridulous.
Leaves:
ocrea 1-veined, 2.5-3 mm, proximal part cylindric, distal part laciniate; petiole 0-1 mm; blade bluish green, narrowly elliptic or oblanceolate, 5-16 × 1-4 mm, margins flat, apex obtuse or acute, papillose-scabridulous; stem leaves 1-1.5(-2) times longer than adjacent branch leaves, distal leaves overtopping flowers.
Inflorescences
axillary; cymes uniformly distributed, 3-6-flowered.
Pedicels
exserted from ocreae, 3-5 mm.
Flowers
closed; perianth 1-1.5 mm; tube 12-27% of perianth length; tepals overlapping, green with white or pink margins, petaloid, not keeled, elliptic, cucullate; midveins unbranched, thickened; stamens 5.
Achenes
enclosed in perianth, black-brown, broadly ovate, 2-3-gonous, 1.5-2 mm, faces subequal, apex not beaked, edges concave, shiny, smooth; late-season achenes common, 2-4 mm.
2
n
= 20.
Flowering May-Oct. Disturbed sites; 50-500 m; introduced; Idaho; e Africa; s Asia; Australia.
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