Amaranthus spinosus L.

Spiny Amaranth; Thorny Amaranth

Herb

Annual

Vascular

Spiny Amaranth is an introduced herbaceous annual in the Amaranth family (Amaranthaceae). It is native to the lowlands of tropical America, but it is now a pantropical weed occurring in warmer areas worldwide. It Alabama it can be found statewide. Spiny Amaranth grows in fields and gardens, in pastures and livestock pens, along roads and railroads, along rivers and lakes, and in other disturbed habitats. It is an annual with a tap root. Stems are erect, glabrous or slightly pubescent, often reddish in color, and much branched. There are a pair of spines at each node. Leaves are alternate, petiolate, ovate to lanceolate in outline, with entire margins. Flowers are unisexual. Staminate flowers are produced in simple or compound terminal spikes. Pistillate flowers are produced in axillary clusters. Flowers are non-showy, and have 5 greenish teapls. The fruit is a utricle (a dry one-seeded fruit enclosed in a papery sack-like structure). Spiny Amaranth leaves and seed are collected and eaten in several countries. It is a serious competitor in row crops, and has been called the world's 15th worst agricultural weed. Because of the spines, livestock and other large herbivores avoid it. Spiny Amaranth can serve as a host for fungi, viruses, and nematodes that attack cultivated plants. Spiny Amaranth is often defoliated by the Amaranth flea beetle (Disonycha glabrata), which is being investigated as a biological control.--A. Diamond

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Not Native

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