Trifolium dubium aka Lesser Trefoil

Trifolium dubium is a small annual in the bean family, Fabaceae. Gardeners know it as lesser trefoil or lesser hop clover. Its native range spans Macaronesia, Europe, the Mediterranean and the Caucasus. It is native to Britain and Ireland. It now grows worldwide in lawns, meadows, roadsides and disturbed ground.

This fast-growing plant forms low mats of thin, tangled stems. Some stems lie flat, while others rise from the ground. They bear a few hairs and have no scent. The RHS describes stems reaching about 0.8 feet [0.25 metres]. Its broader garden size range is 0.3–1.6 feet [0.1–0.5 metres] tall and wide. Small, bright green leaves grow in an alternate pattern. Each leaf has two or three leaflets with slightly curved edges. The foliage is deciduous.

Small yellow flowers appear from May to October. They turn yellow-brown as they age. Each flower has five petals. Long stalks carry groups of three to fifteen flowers. Bees visit for nectar and pollinate the blooms. The flowers are also self-fertile. Each dry legume holds one seed and stays closed when ripe. The seed remains within the calyx. The plant also feeds clouded sulfur butterfly larvae.

Grow lesser trefoil in full sun, with moist soil that drains well. It cannot grow in shade. It accepts chalk, clay, loam and sand, including poor soils. Acid, neutral and alkaline soils all suit it. The RHS rates it H7 for UK conditions. NC State lists USDA zones 8–9. Plants reach their full size within one year. Sow seed to raise new plants; no pruning is needed. It tolerates mowing and foot traffic in lawns. Suggested settings include wildflower meadows, wildlife gardens, gravel gardens and borders.

As a legume, it fixes nitrogen and serves as animal forage. Seed mixes for land reclamation can include it with grasses. Its value in lawns depends on whether clover is welcome. It can spread as a weed, and some US states consider it invasive. The RHS reports few pest or disease problems. NC State warns that it can host a mite affecting nearby plants. This may cause gooseberries to drop fruit or camellias to bud early. PFAF lists no known edible uses or hazards. It records a traditional use of chopped plants on cuts to stem bleeding. That record does not establish safety or medical benefit.