Amaranthus blitoides
matweed, prostrate pigweed

Distribution: Occurring chiefly east of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast; cosmopolitan.

Habitat: Dry, disturbed areas

Flowers: June - September

Origin: Introduced from central United States

Growth Duration: Annual

Conservation Status: Not of concern

Pollination: Wind


Monoecious, glabrous annuals; stems prostrate and forming mats, or ascending, 20-100 cm, heavily branched, green to pale pinkish, glabrous.


Leaves alternate, petiole 3-15 mm; blade generally 10-30 mm long and 4-10 mm broad, obovate to spatulate, base cuneate, apex obtuse, margins entire and flat or slightly wavy.


Inflorescence a cymose axillary cluster, green, 3-flowered; bracts of pistillate flowers 1, narrowly ovate, somewhat leaflike, 1.5-5 mm, equal to or slightly greater than perianth, apex acute.


Staminate flowers perianth parts 3 or 4, 1.5-2.5 mm, stamens usually 3, filaments free, anthers 4-locular; pistillate flowers tepals 4-5, 1.5-3 mm, narrowly ovate to oblong, unequal, outer 2 greater than others, 2-3 mm, stigmas usually 3 and spreading.


Utricles dehiscing along a fissure encircling the whole fruit, 1.7-2.5 mm and generally equaling tepals, somewhat spheric to obovoid, green or sometimes purple, mostly smooth, slightly wrinkled near tip; seeds 1.3-1.7 mm, lenticular, black and dull.

Accepted Name:
Amaranthus blitoides S. Watson
Publication: Proc. Amer. Acad. Arts. 12: 273. (as Amarantus). 1877.

Synonyms & Misapplications:
Amaranthus graecizans L., misapplied [FNA4, HC]
Additional Resources:

PNW Herbaria: Specimen records of Amaranthus blitoides in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Amaranthus blitoides checklist entry.

OregonFlora: Amaranthus blitoides information.

E-Flora BC: Amaranthus blitoides atlas page.

CalPhotos: Amaranthus blitoides photos.

USDA Plants: Amaranthus blitoides information.

9 photographs:
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