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carelessweed, Palmer's amara nth, Palmer's pigweed

Habit Plants glabrous or nearly so.
Stems

erect, branched, usually (0.3–)0.5–1.5(–3) m;

proximal branches often ascending.

Leaves

long-petiolate;

blade obovate or rhombic-obovate to elliptic proximally, sometimes lanceolate distally, 1.5–7 × 1–3.5 cm, base broadly to narrowly cuneate, margins entire, plane, apex subobtuse to acute, usually with terminal mucro.

Bracts

of pistillate flowers with long-excurrent midrib, 4–6 mm, longer than tepals, apex acuminate or mucronulate; of staminate flowers, 4 mm, equaling or longer than outer tepals, apex long-acuminate.

Inflorescences

terminal, linear spikes to panicles, usually drooping, occasionally erect, especially when young, with few axillary clusters, uninterrupted or interrupted in proximal part of plant.

Staminate flowers

tepals 5, unequal, 2–4 mm, apex acute;

inner tepals with prominent midrib excurrent as rigid spine, apex long-acuminate or mucronulate;

stamens 5.

Pistillate flowers

tepals 1.7–3.8 mm, apex acuminate, mucronulate;

style branches spreading;

stigmas 2(–3).

Seeds

dark reddish brown to brown, 1–1.2 mm diam., shiny.

Utricles

tan to brown, occasionally reddish brown, obovoid to subglobose, 1.5–2 mm, shorter than tepals, at maturity walls thin, almost smooth or indistinctly rugose.

Amaranthus palmeri

Phenology Flowering summer–fall, occasionally spring–winter in southern part of its native range.
Habitat Streambanks, disturbed habitats, especially agricultural fields, railroads, waste areas, roadsides
Elevation 100-1000 m (300-3300 ft)
Distribution
from FNA
AR; AZ; CA; CO; FL; GA; IL; KS; KY; LA; MA; MD; MO; MS; NC; NE; NJ; NM; NV; NY; OH; OK; PA; SC; TN; TX; UT; VA; WI; WV; ON; Mexico [Introduced Europe, Asia, and Australia]
[WildflowerSearch map]
[BONAP county map]
Discussion

Originally native to the North American Southwest, from southern California to Texas and northern Mexico, Amaranthus palmeri at present is a successful invasive species, which is evident from its expansion both in eastern North America and overseas. Because of its rapid spread, the distribution data presented here are probably incomplete.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 4, p. 418.
Parent taxa Amaranthaceae > Amaranthus > subg. Acnida > sect. Saueranthus
Sibling taxa
A. acanthochiton, A. albus, A. arenicola, A. australis, A. blitoides, A. blitum, A. californicus, A. cannabinus, A. caudatus, A. crassipes, A. crispus, A. cruentus, A. deflexus, A. dubius, A. fimbriatus, A. floridanus, A. graecizans, A. greggii, A. hybridus, A. hypochondriacus, A. muricatus, A. obcordatus, A. polygonoides, A. powellii, A. pumilus, A. retroflexus, A. scleropoides, A. spinosus, A. tamaulipensis, A. thunbergii, A. torreyi, A. tricolor, A. tuberculatus, A. viridis, A. viscidulus, A. watsonii, A. wrightii
Name authority S. Watson: Proc. Amer. Acad. Arts 12: 274. (1877)
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