Amaranthus palmeri aka Carelessweed

Amaranthus palmeri is an annual in the amaranth family. Common names include Palmer amaranth, Palmer pigweed, and carelessweed. Its native range runs from southern California through Texas into Mexico. It grows in fields and waste ground at low elevations. In California, it also grows in inland valleys and deserts. People have introduced it to Europe, Australia, and other regions. It has spread beyond its native range in North America.

This plant grows upright and forms many branches during summer. NC State gives a usual height of 6–8 feet [1.8–2.4 metres]. Some plants reach 10 feet [3 metres] or more. Useful Tropical Plants reports a lower range of 1.6–4.9 feet [0.5–1.5 metres]. Both accounts describe a branched annual rather than a woody plant. Stems and leaves have smooth surfaces with few or no hairs. The green leaves grow alternately on long stalks. Their blades range from oval to diamond-shaped, with pointed tips. Some leaves show a pale mark shaped like a V. Seen from above, the leaf layout can resemble a poinsettia.

Small green flowers appear in summer and fall. Male and female flowers grow on separate plants. Their spikes can reach 1.5 feet [0.46 metres] long. Female spikes feel prickly, while male spikes feel softer. The seeds have a dark red-brown colour. A single plant can make as many as 500,000 seeds. Seeds sprout fast, and young plants soon gain height. NC State reports growth of up to one inch a day.

Full sun suits this species, which withstands heat and very low rainfall. Useful Tropical Plants recommends fertile soil that drains well. It also calls for a warm site with shelter. PFAF lists USDA zones 6–12 but notes uncertainty about growth in Britain. Its main landscape concern is its ability to spread. It competes strongly with vegetables and field crops in the southern United States. Useful Tropical Plants describes it as invasive beyond its home range. Leaf-chewing insects can also damage the foliage.

People gather its leaves and seeds for food. They cook the leaves as greens or dry them for later use. They grind seeds into flour and cook them with cereals. PFAF also lists stems as edible. The whole plant can supply yellow and green dyes. PFAF reports no known medicinal use for this species.