Ontario Weeds: Prostrate pigweed

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Excerpt from Publication 505, Ontario Weeds, Order this publication

Table of Contents

  1. Name
  2. Other Names
  3. Family
  4. General Description
  5. Stems and Leaves
  6. Flowers and Fruit
  7. Habitat
  8. Similar Species
  9. Related Links

Name: Prostrate pigweed, Amaranthus blitoides S. Wats.,

Other Names: amarante fausse-blite, Prostrate amaranth, Spreading amaranth, Tumbleweed, amarante étalée, amarante basse, amarante charnue, Amaranthus graecizans L.

Family: Amaranth Family (Amaranthaceae)

General Description: Annual, reproducing only by seed.

Photos and Pictures

Prostrate pigweed.

Prostrate pigweed. A. Portion of a prostrate branch. B. Short branch with several clusters of flowers.

Prostrate pigweed. A. Portion of a prostrate branch. B. Short branch with several clusters of flowers.

Stems & Leaves: Stems and leaves prostrate or with tips of some branches raised 2-5cm (1-2in.) above the ground surface, 10-120cm (4in.-4ft) long, much-branched and often forming thick, circular mats, usually not rooting from the nodes, green or purplish-red, somewhat fleshy; leaves alternate (1 per node), numerous along the branches, 1-5cm (2/5-2in.) long, the blade paddle-shaped, light green or sometimes a bit reddish, rounded or slightly indented at the end and usually ending in a short, very soft spine, not succulent.

Flowers & Fruit: Flowers very small (3mm, 1/8in. long), greenish, without petals; sepals narrow, bract-like; 2 or more flowers plus several narrow bracts in clusters on short lateral branches in the axils of small leaves; each flower unisexual, either female (seed-producing) with only a pistil or male (pollen-producing) with only stamens; seeds black, disk-shaped, about 1.5mm (1/16in.) in diameter. Flowers from June to September.

Habitat: Prostrate pigweed occurs throughout southern Ontario in waste areas, roadsides, gardens and in some row crops, usually on coarse or sandy soils.

Similar Species: It is distinguished from Tumble pigweed by its prostrate habit, its narrow bracts about the same length as the sepals and its larger seed; from Redroot, Smooth and Green pigweed by its prostrate habit, its flowers in small clusters on very short branches in the axils of leaves, the absence of large, terminal inflorescences and by its larger seeds; from Purslane by its thinner leaves with pointed tips, its clusters of narrow-bracted flowers and its relatively non-succulent nature.

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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