15. Amaranthus viridis L.
A. gracilis Poir.
Map 824
Plants
monoecious. Stems 30–120 cm long, ascending or more or less spreading with
ascending branches, glabrous or sparsely pubescent with inconspicuous mostly
multicellular hairs toward the tip, unarmed. Leaves mostly long-petiolate. Leaf
blades 2–8 cm long, elliptic to ovate or broadly ovate, narrowed or tapered to
a usually bluntly pointed tip (often minutely notched at the very tip),
narrowed or tapered at the base, the undersurface glabrous or sparsely pubescent
along the main veins with inconspicuous mostly multicellular hairs.
Inflorescences dull or dark green, axillary and terminal, the axillary
inflorescences of elongate spikes, the terminal inflorescence a spike or
panicle with few to several, long, ascending branches from near the base, the
flowers often grouped into discontinuous clusters or regions along the basal
portions of the spikes, the tip somewhat curved or nodding, the main axis and
branches sparsely to moderately pubescent with inconspicuous, mostly
multicellular hairs. Bracts 0.6–0.9 mm long, shorter than the sepals and
fruits, ovate to oblong-ovate, narrowed or tapered to a sharply pointed tip,
with a somewhat thickened green midrib and relatively broad, thin, papery
margins, the midrib sometimes extending beyond the main body as a minute, short
point, not spinelike. Staminate flowers with 3 more or less similar sepals,
these 0.9–1.2 mm long, erect or ascending, oblanceolate to oblong-oblanceolate,
abruptly tapered to a sharply pointed tip, the midrib sometimes extending
beyond the main body as a minute, short point, not spinelike. Stamens 3.
Pistillate flowers with 3 more or less similar sepals, these 0.9–1.2 mm long,
erect or ascending, oblanceolate to oblong-oblanceolate, abruptly tapered to a
sharply pointed tip, the midrib sometimes extending beyond the main body as a
minute, short point, not spinelike. Stigmas 3, erect. Fruits 1.4–1.7 mm long,
indehiscent, the surface usually strongly wrinkled when dry. Seeds 1.0–1.3 mm
in diameter, angled along the rim, the surface reddish brown to black. 2n=34.
July–October.
Introduced,
known thus far from a single historical collection from Jackson County
(originally probably native to South America; now widely introduced in tropical
and warm-temperate regions nearly worldwide; in the U.S. introduced in states
along the Atlantic coast and west along the southern tier of states to
Arizona). Open, disturbed areas.
Amaranthus
viridis somewhat
resembles A. blitum in its slender, somewhat flexuous spikes, small
flowers, indehiscent fruits, relatively weak stems, and broad leaves. Aside
from quantitative differences noted in the two descriptions, it differs most
notably in having leaf blades at most minutely notched at the tip, the axillary
inflorescences elongate of spikes usually nearly as long as the terminal ones,
and in its 3 sepals that are broadest above the midpoint.