OregonFlora: Amaranthus muricatus vs. Amaranthus albus

	Amaranthus muricatus	Amaranthus albus
		tumbling pigweed, white pigweed
Habit		Plants glabrous to sparsely whitish-viscid pubescent, 1–10 dm; larger plants forming tumbleweeds.
Stems		usually erect, sometimes nearly prostrate, spreading and branched, green to whitish.
Leaves		blades obovate to narrowly spatulate, 1–8 cm, bases wedge-shaped; margins flat to distinctly wavy-crisped; midveins extending to a short weak spine; tips rounded; petioles 5–40 mm.
Inflorescences		axillary clusters of flowers, green; greenish white, or yellow, staminate and pistillate flowers intermixed in clusters; bracts rigid, oblong to lanceolate, 2–3(3.5) mm.
Staminate flowers		few; perianth segments 3; stamens 3.
Pistillate flowers		perianth segments 3; styles 3; erect.
Fruits		ellipsoid-ovoid, 1.5 mm, rugose at bases.
Seeds		lenticular, 0.6–1 mm; black; smooth; shiny.
2n		=32.

	Amaranthus muricatus	Amaranthus albus
Distribution	[BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion		Disturbed areas, fields. Flowering Jun–Oct. 0–1300 m. BR, BW, Casc, Col, Est, Lava, Owy, Sisk, WV. CA, ID, NV, WA; nearly worldwide. Exotic. Amaranthus albus is a highly variable taxon depending on environmental conditions. It can be confused with A. blitoides when young and in moist areas where it is known to have a more procumbent habit.
Source		Flora of Oregon, volume 2, page 65 Bridget Chipman
Sibling taxa	A. albus, A. blitoides, A. californicus, A. deflexus, A. hybridus, A. hypochondriacus, A. powellii, A. retroflexus, A. viridus	A. blitoides, A. californicus, A. deflexus, A. hybridus, A. hypochondriacus, A. powellii, A. retroflexus, A. viridus
Web links	Local Web sites: 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 muricatus

Amaranthus albus

tumbling pigweed, white pigweed

Habit

Plants glabrous to sparsely whitish-viscid pubescent, 1–10 dm; larger plants forming tumbleweeds.

Stems

usually erect, sometimes nearly prostrate, spreading and branched, green to whitish.

Leaves

blades obovate to narrowly spatulate, 1–8 cm, bases wedge-shaped;

margins flat to distinctly wavy-crisped;

midveins extending to a short weak spine;

tips rounded;

petioles 5–40 mm.

Inflorescences

axillary clusters of flowers, green; greenish white, or yellow, staminate and pistillate flowers intermixed in clusters;

bracts rigid, oblong to lanceolate, 2–3(3.5) mm.

Staminate flowers

few;

perianth segments 3;

stamens 3.

Pistillate flowers

perianth segments 3;

styles 3; erect.

Fruits

ellipsoid-ovoid, 1.5 mm, rugose at bases.

Seeds

lenticular, 0.6–1 mm; black; smooth; shiny.

=32.

Amaranthus muricatus

Amaranthus albus

Distribution

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Disturbed areas, fields. Flowering Jun–Oct. 0–1300 m. BR, BW, Casc, Col, Est, Lava, Owy, Sisk, WV. CA, ID, NV, WA; nearly worldwide. Exotic.

Amaranthus albus is a highly variable taxon depending on environmental conditions. It can be confused with A. blitoides when young and in moist areas where it is known to have a more procumbent habit.

Source

Flora of Oregon, volume 2, page 65
Bridget Chipman

Sibling taxa