Galeopsis speciosa aka Large Flower Hemp Nettle

Galeopsis speciosa is an annual in the mint family, Lamiaceae. Its common names include large-flowered hemp nettle and penboeth amryllw. Its native range stretches from Europe into Siberia. It grows in temperate regions and is native to Britain and Ireland. In Britain, it occurs across much of the country. Scotland holds a strong share of its wild populations.

This bushy wildflower grows up to 3.3 feet [1 metre] tall. It reaches its full size within one year. Its stems are square, with oval leaves that have toothed edges. The foliage is deciduous. Pale yellow flowers grow in whorls toward the stem tops. Each flower has a hood and a purple lower lip. The blooms appear from midsummer into autumn. Their two colours give the flowers a clear contrast. The flowers supply both nectar and pollen for visiting insects.

Wild plants grow in fields, waste ground, and other disturbed places. Plants For A Future also records arable sites with dark, peaty soil. In gardens, it accepts full sun or partial shade. The RHS lists both clay and loam as suitable soils. It also accepts acid, neutral, and alkaline soil. Keep the ground moist while allowing excess water to drain. The plant tolerates varied conditions when the soil stays reasonably moist. East-, south-, and west-facing sites can suit it. It can grow in either open or sheltered positions. The RHS gives it a UK hardiness rating of H5.

Its flowers make it a choice for wildlife gardens. Grow it from seed; it needs no pruning. The RHS reports few usual pest or disease problems. Its annual habit means it completes its growth within one year. Plants For A Future does not flag it as weedy. This sits alongside its known presence on disturbed ground. Those habitat records describe where it grows, not evidence of invasive spread.

Do not treat this plant as food. Plants For A Future rates its edible value at zero. The same source warns that poisoning can cause paralysis. It lists no known medicinal use and gives that value zero. The seeds yield a drying oil used to polish leather. That practical use does not establish that the oil is safe to eat.