13. Amaranthus tricolor L. (Chinese spinach, Malabar spinach)

Map 822

Plants monoecious. Stems 40–150(–200) cm long, erect or ascending, glabrous, unarmed. Leaves long-petiolate. Leaf blades 3–15 cm long, ovate to broadly triangular-ovate, narrowed or tapered to a bluntly or sharply pointed tip (often minutely notched at the very tip), tapered at the base, glabrous. Inflorescences green, often reddish-tinged; axillary and terminal; the axillary inflorescences dense, globose clusters, present at nearly every node; the terminal inflorescence sometimes reduced or absent, otherwise a spike or panicle with relatively few, long, ascending branches from near the base; the flowers mostly continuous along the spikes; the tip straight or often curved to nodding; the main axis and branches glabrous. Bracts 3–6 mm long, longer than the sepals and fruits, ovate to elliptic-ovate, narrowed or tapered to a sharply pointed tip, with a narrow, slightly thickened, green midrib and relatively broad, thin, papery margins, the midrib extending beyond the main body as a short awn, spinelike at maturity. Staminate flowers with 3 more or less similar sepals, these 2.5–4.0 mm long, ascending or somewhat outward-curved at the tip, lanceolate to ovate to elliptic-ovate, narrowed or tapered to a sharply pointed tip, often tapered to a short, awnlike extension of the midrib. Stamens 3. Pistillate flowers with 3 more or less similar sepals, these 2–4 mm long, somewhat outward-curved at the tip, ovate to elliptic-ovate, narrowed or tapered to a stiff, sharply pointed tip, often tapered to a short, awnlike extension of the midrib. Stigmas 2 or 3, spreading from a short, thickened base. Fruits 1.8–2.5 mm long, with circumscissile dehiscence, the surface finely wrinkled when dry. Seeds 1.0–1.3 mm in diameter, rounded along the rim, the surface reddish brown to black. 2n=34. August–October.

Introduced, known only from the city of St. Louis (native of Asia and Malesia; introduced widely in tropical and warm-temperate regions nearly worldwide, in the U.S. sporadically from Michigan to Louisiana). Railroads.

This species, which is cultivated as a salad green and potherb in Asia, was first reported for Missouri by Mühlenbach (1979). Aellen (1959) proposed a complicated infraspecific classification for this species. The single specimen from Missouri is apparently ssp. tricolor, but it does not key well to these subspecies.