Weed Risk Assessment: Amaranthus spinosus

Description: An annual herb reproducing by seed only. Distinguished by flowers and pairs of spiny bracts that occur in the leaf axils. Mature plants are erect, branched and may grow to 1.2 m tall (see Figure 1). Stems are angled in cross section, reddish, fleshy and bear many spines. Leaves are alternate, ovate-rhombic to lanceolate sometimes with sparse hairs on the lower surface and most with a pair of long, straight spines at the base. Flower heads are either a long terminal spike or clumped at the leaf axils in the lower part of the plant. Male and female flowers are small, greenish and occur on the same plant. Fruit is ovoid and contains compressed, shiny, tiny, dark red to black seeds. (HEAR website).