Arctium lappa aka Great Burdock

Arctium lappa, or greater burdock, belongs to the aster family. This fast-growing biennial comes from temperate Eurasia. Kew places its native range from western and central Siberia into Central Asia. It now grows in many other parts of the world. In North America, it spreads through roadsides, fields, and disturbed ground. People grow it for food and traditional herbal use.

The first year brings a low, dense rosette of leaves. Tall, branching stems rise in the second year. Garden plants reach about 5–8 feet (1.5–2.5 metres). Some reach 10 feet (3 metres), according to NC State. Plants spread about 3–5 feet (1–1.5 metres). Large, green, heart-shaped leaves give the plant a coarse look. Woolly hairs cover their undersides. The largest leaves sit near the base. Leaves grow smaller farther up the stem. A deep, fleshy taproot makes established plants hard to remove.

Purple flowerheads form clusters on the leafy branches. NC State lists autumn as the flowering season. Each rounded head holds many small, tubular disk flowers. Hooked bracts surround the heads, which later become brown burs. These catch on fur, feathers, and clothes, spreading the seeds. The small, dry fruits are achenes with fine bristles. Bees visit the flowers for nectar. Some moth larvae feed on the plant, including its roots.

Grow it in sun or partial shade. It prefers moist, well-drained soil with plenty of organic matter. It accepts clay, loam, or sand and a broad pH range. NC State lists USDA zones 3–10; RHS gives UK hardiness H4. Sow seed to raise new plants. RHS suggests wildlife gardens and says pruning is not needed. Yet its spread can outweigh its value in a garden. Deep roots and long-lived seeds make control hard. It can crowd out native plants. RHS reports few pest or disease problems. NC State notes powdery mildew and root rot.

Roots are the main food crop, including in Japan and Korea. Harvest first-year roots before they turn tough and fibrous. Young leaves and unopened flower stalks are also edible. PFAF also lists seeds as edible, but warns about their hairs. Airborne bristles can harm eyes, skin, and airways in people and animals. Burs can trap small birds and bats. Allergic reactions are possible, and PFAF warns against use during pregnancy.