Foliage. Leaves are smooth, simple, alternate along the stems and often have a white arrow-shaped watermark on the upper leaf surface. Stems are smooth.
Spines. Unlike other pigweed species, there are sharp, stiff spines located at the leaf axils.
Flowers are long, terminal spikes.
Life cycle: summer annual.
Toxic Plant: Cattle and swine are the animals most likely to be affected; goats and sheep can also be poisoned. Leaves, stems and roots are toxic. The most common symptom in cattle is bloat as it accumulates nitrates. Because of the spines, it is not likely to be grazed unless there are no other available forages.