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. Both male and female flower parts become stiff and spiny at maturity. 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. 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.
As in monolepis, the nitrate is not poisonous, but can be changed quickly into the toxic nitrite by enzymatic action.