Lotus pedunculatus (formerly Lotus uliginosus), the big trefoil, greater bird's-foot-trefoil or marsh bird's-foot trefoil, is a member of the pea family (Fabaceae).
It is a herbaceous perennial growing throughout Europe in damp, open locations. As one common name suggests, it is a larger plant than related Lotus species, growing 20- tall, with leaflets 10- long and 10- broad. Five to twelve golden-yellow flowers 10- long are borne in an umbel at the tip of the upright stem.
Unlike related species, the stem is always hollow, and the sepals turn back at their tips - these sepal tips form a characteristic "green star" at the end of the flower bud. The peak flowering period in the United Kingdom is June and July.[1]
Lotus pedunculatus has been introduced to the western side of the United States and is now a prevalent weed in irrigated lawns and draining waste areas. Due to this it is considered a problem in gardens across the west and as a legume promotes other weed growth as a nitrogen fixer.[2]
Lotus pedunculatus occurs in a wide range of neutral, damp, open habitats, including certain fen-meadow plant associations such as Juncus subnodulosus-Cirsium palustre fen-meadow habitat.[3]
Lotus pedunculatus is also a host plant for ovipositioning of the wood white butterfly, Leptidea sinapis.[4]