Ontario Weeds: Water smartweed
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Excerpt from Publication 505, Ontario Weeds,
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Table of Contents
- Name
- Other Names
- Family
- Terrestrial or dry habitat forms
- Aquatic forms
- Flowers
- Habitat
- Similar Species
- Related Links
Name: Water smartweed, Polygonum
amphibium L.,
Other Names: renouée amphibie,
renouée aquatique, P. natans (Michx.)
Family: Buckwheat or Smartweed Family
(Polygonaceae)
Water smartweed.Top of flowering plant.
Terrestrial or dry habitat forms: With
stems erect to nearly prostrate, smooth or more or less hairy; leaves
alternate, lanceolate to oblong, up to 20cm (8in.) long; ocrea membranous
or slightly leaf-like in texture, its outer margin smooth or torn
and either with or without a distinct horizontal, leaf-like flange.
Aquatic forms: Rooting in shallow water
with floating, hairless stems, elliptic leaves and ocreae without
horizontal, leaf-like flanges.
Flowers: Inflorescence of both forms
a compact, ovoid- or conic-cylindric, spike-like raceme, 1-4cm (2/5-1¼in.)
long and 1-1.7cm (2/5-2/3in.) wide, usually blunt; flowers light
to deep pink, without true petals, the coloured sepals 2-5mm (1/12-1/5in.)
long. Both terrestrial and aquatic forms have a thick, lens-lens-shaped,
pale brown to nearly black achene, 2.5mm (1/10in.) long and wide.
Flowers from June to September.
Habitat: Water smartweed is a native
plant in shallow water and along the margins of lakes, ponds, rivers,
creeks and roadside ditches, and persists in depressional areas
in cultivated fields throughout Ontario.
Similar Species: Both terrestrial
and aquatic forms of Water smartweed are distinguished from the
closely related Swamp
smartweed by their short, thick, more or less cylindric inflorescences,
the occasional presence of pubescence and a leaf-like flange on
the ocrea of the terrestrial form, and from most other Smartweeds
by having thick, tough, forking rhizomes.
Related Links
... on general Weed
topics
... on weed identification, order OMAFRA
Publication 505: Ontario Weeds
... on weed control, order OMAFRA
Publication 75: Guide To Weed Control
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