Amaranthus albus aka Prostrate Pigweed

Amaranthus albus belongs to the amaranth family, Amaranthaceae. It is an annual, which means it lives for one year. Common names include white pigweed, white amaranth, and prostrate pigweed. It comes from southern North America and grows on disturbed ground. It also grows across much of Europe, beyond its native range. In some parts of Europe, it has settled and persists. Elsewhere in Europe, it appears only from time to time. It is not native to Britain or Ireland.

Plants reach about 1–2.3 feet [0.3–0.7 metres] tall. Their stems branch near the base of the plant. Most plants stand upright or rise at an angle. Some grow close to the ground instead of standing upright. The name prostrate pigweed does not mean it always creeps. These forms help explain why it has different common names. In Britain, it has leaves from May through October.

Plants For A Future gives July and August as flowering months. Each plant has male flowers and separate female flowers. Wind spreads the pollen, but plants can also fertilise themselves. Seeds ripen from September to October in thin, papery capsules. These capsules form cases that hold the seeds. Most seeds are small, hard, shiny, and black. A few have a reddish-brown tint instead of black. Ripe seeds fall free from their cases with little effort. Winnowing uses air to blow their light chaff away.

The plant needs sun and prefers moist soil that drains well. It can grow in sand, loam, or clay. Soil can be mildly acid, neutral, or mildly alkaline. Useful Tropical Plants calls for a warm, sheltered site. Plants For A Future lists USDA zones 4–10. It also warns that the plant is frost tender. Sow seeds outdoors in late spring, when the soil warms. Protect earlier sowings under glass until the risk of frost passes. Insects that chew leaves can harm the plants. The species can also become a weed.

People gather both the leaves and seeds for food. They cook leaves and young plants to use like spinach. They toast seeds, boil them as porridge, or grind them into flour. Seeds can also go into seed bars. The sources warn that leaves may build up nitrates. This can happen when the soil is rich in nitrogen. The soil's nutrient level thus matters when growing it for food. The whole plant also yields yellow and green dyes. Plants For A Future lists no known medicinal uses.