6. Amaranthus cruentus L.

Map 815

Plants monoecious. Stems 40–200 cm long, erect or ascending, sparsely to moderately pubescent toward the tip with inconspicuous, mostly crinkled, multicellular hairs, unarmed. Leaves long-petiolate. Leaf blades 2–25 cm long, lanceolate to ovate or elliptic, narrowed or tapered to a usually sharply pointed tip, narrowed or tapered at the base, the surfaces glabrous or the undersurface sparsely pubescent mostly along the veins with inconspicuous, mostly crinkled, multicellular hairs. Inflorescences usually red, less commonly bright green or yellow, axillary and terminal, the axillary inflorescences short to long spikes, the terminal inflorescence usually a panicle with numerous clusters of short to long, dense spikes (these branching along most of the panicle axis), the flowers mostly continuous along the spikes, the tip curved or nodding, the main axis and branches moderately to densely pubescent with mostly crinkled, multicellular hairs. Bracts 1.2–2.0 mm long, shorter than to about as long as the fruits, lanceolate to ovate, narrowed or tapered to a sharply pointed tip, with a slightly thickened green midrib and broad, thin, papery margins, the midrib extending beyond the main body as a short awn, often somewhat spinelike at maturity. Staminate flowers with 5 more or less similar sepals, these 1.0–1.7 mm long, straight, oblong-elliptic to oblong-ovate, narrowed or tapered to a bluntly or more commonly sharply pointed tip, usually with a minute, awnlike extension of the midrib. Stamens 5. Pistillate flowers with 5 more or less similar sepals, these 1.0–1.6 mm long, slightly and inconspicuously overlapping, erect at the tip, narrowly oblong to narrowly oblong-elliptic, rounded to bluntly pointed, often with a minute, awnlike extension of the midrib. Stigmas (2)3, erect or nearly so. Fruits 1.4–1.8 mm long, with circumscissile dehiscence, the surface smooth or finely wrinkled above the midpoint when dry. Seeds 1.0–1.3 mm in diameter, angled along the rim, the surface dark brown. 2n=32, 34. July–October.

Introduced, uncommon and sporadic in Missouri (originated in South America, widely cultivated in tropical and warm-temperate regions, escaping sporadically in the U.S.). Gardens and open, disturbed areas.

Amaranthus cruentus is one of the cultigens derived long ago in the Andean region from selected strains of A. hybridus. Like A. caudatus, it is one of the principal crop amaranths, but in the United States it is cultivated more commonly as an ornamental for its long, drooping, red inflorescences.

Steyermark (1963) reported two specimens from Boone County as representing escapes of A. hypochondriacus L. (as A. hybridus var. hypochondriacus), but these specimens subsequently were redetermined as A. cruentus (Costea et al., 2001a).