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blood amaranth, caterpillar amaranth, purple amaranth, red amaranth

Watson's amaranth

Habit Plants almost glabrous or slightly pubescent distally, especially when young. Plants pubescent and glandular-pubescent, especially on bracts.
Stems

erect, green or reddish purple, branched distally, mostly in inflorescence, to nearly simple, 0.4–2 m. Leaves: petiole 1/2 as long as to ± equaling blade;

blade rhombic-ovate or ovate to broadly lanceolate, 3–15(–20) × 1.5–10(–15) cm, occasionally larger in robust plants, base cuneate to broadly cuneate, margins entire, plane, apex acute or subobtuse to slightly emarginate, with mucro.

ascending to erect, usually much-branched, 0.1–1 m;

branches usually ascending.

Leaves

petiole shorter than or equaling blade;

blade ovate, obovate to elliptic, or oblong-elliptic, 1–8 × 0.5–4 cm, base broadly cuneate to nearly rounded, margins entire, plane or slightly undulate, apex obtuse to emarginate, usually with terminal mucro.

Bracts

narrowly spathulate, 2–3 mm, equaling or slightly longer than tepals, apex short-spinescent.

of pistillate flowers with long-excurrent midrib, 3–4 mm, longer than tepals, apex long-acuminate or mucronulate; of staminate flowers 2.5–4 mm, usually equaling outer tepals, apex long-acuminate or mucronulate.

Inflorescences

terminal and axillary, erect, reflexed, or nodding, usually dark red, purple, or deep beet-red, less commonly almost green or greenish red, leafless at least distally, large and robust.

mostly terminal, erect spikes to panicles, usually thick and uninterrupted, with few axillary clusters in basal part of plant.

Staminate flowers

at tips of inflorescences;

tepals 5;

stamens (4–)5.

tepals 5, equal or subequal, 1.5–2(–3) mm, apex acute or almost obtuse;

inner tepal apex acuminate or mucronulate;

stamens 3–5.

Pistillate flowers

tepals 5, oblong to lanceolate, not clawed, equal or subequal, 1.5–3 mm, apex acute;

style branches erect or slightly reflexed;

stigmas 3.

tepals with dark midribs not excurrent, spatulate to fan-shaped, 1.7–2.2 mm, apex obtuse, with terminal mucro;

style branches spreading;

stigmas 2(–3).

Seeds

usually white or ivory, with reddish or yellowish tint, sometimes dark brown to dark reddish brown, broadly lenticular to elliptic-lenticular, 1.2–1.6 mm diam., smooth or indistinctly punctate.

dark reddish brown to nearly black, (0.8–)1–1.2 mm diam., shiny.

Utricles

obovoid to elongate-obovoid, 2–2.5 mm, smooth or slightly rugose distally, dehiscence regularly circumscissile.

light brown to brown, obovoid to subglobose, 1.5–2 mm, shorter than tepals, walls thin, smooth or indistinctly rugose.

Amaranthus cruentus

Amaranthus watsonii

Phenology Flowering summer–fall. Flowering late winter–spring, summer–fall.
Habitat Near places of cultivation Coastal dunes, beaches, sandy inland areas, weakly saline flats
Elevation 0-100 m (0-300 ft)
Distribution
from FNA
AZ; CA; CT; IL; IN; KY; MA; MD; ME; MI; NC; NE; NH; NJ; NY; OH; OR; PA; RI; SC; TX; UT; VT; WA; WI; WV; Central America; South America; cultivated widely
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; CA; Mexico (Baja California, Baja California Sur, Sonora); Europe (reported as rare, non-naturalized casual alien)
[WildflowerSearch map]
[BONAP county map]
Discussion

Amaranthus cruentus is cultivated as ornamental and pseudocereal almost worldwide from tropical to warm-temperate regions. While reported as naturalized in several states, most specimens identified as this species are referable to A. hybridus or other native species. Escaped plants of A. cruentus sometimes occur near places of cultivation (see note under A. caudatus). No attempt has been made to summarize distribution data for such escapes.

Amaranthus cruentus originated from A. hybridus (most probably in cultivation in Central America), with which it shares almost all major morphologic characteristics. Inclusion of cultivated forms in A. hybridus in a broad sense is thus rather justified. Cultivated species traditionally have been treated as separate taxa in horticultural and agricultural literature, and we prefer to maintain the current convenient usage of these names.

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

Source FNA vol. 4. FNA vol. 4, p. 418.
Parent taxa Amaranthaceae > Amaranthus > subg. Amaranthus 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. deflexus, A. dubius, A. fimbriatus, A. floridanus, A. graecizans, A. greggii, A. hybridus, A. hypochondriacus, A. muricatus, A. obcordatus, A. palmeri, 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
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. palmeri, 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. wrightii
Synonyms A. hybridus subsp. cruentus
Name authority Linnaeus: Syst. Nat. ed. 10, 2: 1269. (1759) Standley: Bull. Torrey Bot. Club 41: 505. (1914)
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