Burke: Amaranthus palmeri vs. Amaranthus blitoides

	Amaranthus palmeri	Amaranthus blitoides
		matweed, prostrate pigweed
Habit		Monoecious, glabrous annuals; stems prostrate and forming mats, or ascending, 20-100 cm, heavily branched, green to pale pinkish, glabrous.
Leaves		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		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.
Flowers		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.
Fruits		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.

	Amaranthus palmeri	Amaranthus blitoides
Flowering time		June - September
Habitat		Dry, disturbed areas
Distribution	[WildflowerSearch map] [BONAP county map]	Occurring chiefly east of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast; cosmopolitan. [WildflowerSearch map] [BONAP county map]
Origin		Introduced from central United States
Conservation status		Not of concern
Sibling taxa	A. albus, A. blitoides, A. blitum, A. californicus, A. caudatus, A. cruentus, A. deflexus, A. hybridus, A. hypochondriacus, A. powellii, A. retroflexus, A. tuberculatus	A. albus, A. blitum, A. californicus, A. caudatus, A. cruentus, A. deflexus, A. hybridus, A. hypochondriacus, A. powellii, A. retroflexus, A. tuberculatus
Web links	Local floras: CA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Amaranthus palmeri

Amaranthus blitoides

matweed, prostrate pigweed

Habit

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

Leaves

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

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.

Flowers

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.

Fruits

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.