Amaranthus spinosus L.
spiny amaranth
Glabrous erect, annual herb with stout, angular stems to c. 1 m high. Petioles slender, to c. 5 cm long. Lamina of infl.-lvs to c. 5 × 1.5 cm, ovate-lanceolate to oblong; veins prominently elevated below; base cuneate to attenuate; apex obtuse, usually with prominent mucro. Infl. to c. 10 cm long, green; terminal spikes slender; main branch much > lateral branches. Lower fl. clusters compact, all ♀, at least some with a pair of spines 6-12 mm long. Longer bracteoles 2.5-3 mm long, ovate with subulate tip and green keel; shorter bracteoles 2-2.5 mm long. Tepals 4-5, 1.5-2 mm long, oblong-obovate, green; keel narrow; apex acute or mucronate. Fr. ovoid-ellipsoid, circumscissile, not exceeding tepals. Seed 0.7-1 mm diam., orbicular, dark brown.
N.: known from Whangarei only, where it was probably brought in accidentally with nursery stock and was first collected in 1970.
Probably New World Tropics 1975
FL Jan-Feb.