Spiny Pigweed, Amaranthus spinosus
Spiny pigweed, also called spiny amaranth, is an annual weed with hairless stems and leaves and a reddish tinge. Leaves are alternate and range from 1.5 to 2.5 inches in length, and there are two sharp spines at each node. Although it has been associated with nitrate accumulation in livestock, Spiny Pigweed is not normally the species identified. Since it is not highly palatable, livestock overgrazing forages and leaving bare ground allow opening for spiny pigweed to take over entire pastures.