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slender pigweed, slim amaranth

redroot amaranth, rough pigweed

Habit Plants mostly glabrous, villous distally when young. Plants densely to moderately villous, especially in distal portions.
Stems

erect, branched or not, 3–12(20) dm, green or red.

erect, 1.5–15(20) dm; simple or branched distally, green or reddish.

Leaves

blades rhombic-ovate to widely lanceolate; (2)4–12(15) cm, bases wedge-shaped;

margins entire; plane;

tips acute to obtuse;

midveins extending to a spine;

petioles 1–5(10) cm.

blades ovate to rhombic-ovate, 2–15 cm, bases wedge-shaped;

margins entire; flat to crisped;

midveins extending to a short spine;

tips acute to obtuse;

petioles 2.5–8 cm.

Inflorescences

terminal and axillary, tightly clustered; lax and nodding; dull green to red, villous;

bracts 2–4 mm;

midveins extending to a spine.

terminal and axillary; erect to somewhat reflexed tightly clustered panicles, green to silvery green;

bracts numerous, lanceolate to awl-shaped, 3–6 mm.

Flowers

perianth segments 5, mostly similar in staminate and pistillate flowers; erect, not overlapping or reflexed, linear to lance-oblong;

midveins extending to spine;

tips acute.

perianth segments similar in staminate and pistillate flowers; spoon-shaped to obovate, overlapping, reflexed with age; equal to subequal;

midveins extending to a short spine;

tips rounded to notched.

Staminate flowers

generally at inflorescence tips;

perianth segments of nearly equal length, 2–3 mm;

stamens 5.

perianth segments 4–5, 2–3 mm;

stamens (3)4–5.

Pistillate flowers

perianth segments of equal length or 1 slightly longer, 1.5–2 mm;

styles 3; erect.

perianth segments 5; (2)2.5–3.5 mm;

stigmas 3.

Fruits

ovoid, 1.5–2.2 mm, rugose at tips; smooth below; dehiscence circumscissile.

ovoid to elliptic, 1.5–2.5 mm; smooth to rugose at bases; dehiscence usually circumscissile.

Seeds

lenticular, widely orbicular to rounded, 1–1.4 mm, red-brown to black; shiny.

lenticular; ovoid to obovoid, 1–1.3 mm, dark brown to black; shiny.

2n

=32.

=34.

Amaranthus hybridus

Amaranthus retroflexus

Distribution
[WildflowerSearch map]
[BONAP county map]
[WildflowerSearch map]
[BONAP county map]
Discussion

Disturbed areas, streambanks, roadsides, fields. Flowering May–Oct. 0–700 m. Casc, Owy, Sisk, WV. CA, ID, NV, WA; throughout North America; scattered worldwide. Native?

Amaranthus hybridus has been known to hybridize with A. retroflexus.

Disturbed areas, fields, roadsides, streambanks. Flowering Jun–Sep. 0–1500 m. BW, Lava, Owy, Sisk, WV. CA, ID, NV, WA; worldwide. Exotic?

See also A. hybridus.

Source Flora of Oregon, volume 2, page 66
Bridget Chipman
Flora of Oregon, volume 2, page 66
Bridget Chipman
Sibling taxa
A. albus, A. blitoides, A. californicus, A. deflexus, A. hypochondriacus, A. powellii, A. retroflexus, A. viridus
A. albus, A. blitoides, A. californicus, A. deflexus, A. hybridus, A. hypochondriacus, A. powellii, A. viridus
Web links