An Illustrated Guide to ARIZONA WEEDS

The University of Arizona Press

PALMER AMARANTH, carelessweed


PIGWEED FAMILY--Amaranthaceae

PALMER AMARANTH-Amaranthus palmeri Wats.

DESCRIPTION-Palmer amaranth is a tall stout summer annual 1 to 6 (excep tionally 15 ) feet high, reproducing by seeds. There is 1 thick principal stem, and the lateral branches are usually short. The stem often turns red, particularly in age. The lanceolate or eggshaped, sometimes varigated leaves are alternate, hairless, 2 to 8 inches long including the long stalks, 1/2 to 2 1/2 inches broad, with very prominent whitish veins on the lower surface.

The inconspicuous flowers are of 2 kinds, male and female, borne on separate plants in long leafless branching spikes at the top of the plant. The slender central flowering tassel, 1/2 to 1 1/2 feet long, is much longer than any of the side branches at its base. Both male and female flower parts become stiff and spiny at maturity. The dark reddish brown seed is oval, and about 1/16 inch long.

DlSTRlBUTION-One of the most common weeds in moist disturbed soils in central and southern Arizona, it also occurs in the northern part of the state. It is a great pest in and around cultivated fields, ditch banks, roadsides, and irrigated pastures, and in all summer crops, especially serious in cotton and sorghum. It also abounds in river bottoms, canyon beds, and on overgrazed ranges in the desert and desert grassland; 100 to 5,500 feet elevation; flowering all summer, May to November.

The pollen of palmer amaranth often causes hay fever. The plant is relished by livestock in all stages of growth, and is sometimes cut for hay or put into silos. Many stockmen consider it good feed.

POISONOUS PROPERTIES-Palmer amaranth contains nitrate varying from a trace to over 9 percent. As in monolepis, the nitrate is not poisonous, but can be changed quickly into the toxic nitrite by enzymatic action.

Copyright (c) 1972 The Arizona Board of Regents

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