Spiny pigweed (Amaranthus spinosus) is an erect, often bushy, multi-branched summer annual with rigid, sharp spines. It's leaves are diamond-shaped to egg-shaped with the broader end closest to the stem, and many are variegated with a v-shaped watermark or lighter colored-area. Each leaf node along stems contains a pair of rigid, sharp spines. The stems are reddish, smooth, upright and branched. It's flowers a tiny green auxillary clusters of terminal spikes that appear slightly different depending on whether it is a male or female plant. A. spinosus is a common weed found in pastures of horses living in tropical or subtropical climates. Like other pigweeds, A. spinosus develops a strong taproot with a network of fibrous feeder roots. The taproot may or may not be distinctly reddish in color.
Toxic components
The plant is a nitrate accumulator and can develop high levels of nitrates under certain environmental conditions which can cause nitrate toxicity in ruminants.
