Lotier Des Marais

Foodplant / internal feeder
larva of Apion ebeninum feeds within stem of Lotus pedunculatus
Other: major host/prey

Foodplant / internal feeder
larva of Apion modestum feeds within pod of Lotus pedunculatus
Other: sole host/prey

Foodplant / saprobe
basidiome of Calyptella campanula is saprobic on dead, decayed stem of Lotus pedunculatus

In Great Britain and/or Ireland:
Foodplant / parasite
conidial anamorph of Erysiphe trifolii parasitises live Lotus pedunculatus

Foodplant / pathogen
sporangium of Peronospora corniculata infects and damages live Lotus pedunculatus
Other: minor host/prey

Foodplant / parasite
sporangium of Peronospora lotorum parasitises live Lotus pedunculatus
Other: minor host/prey

Foodplant / parasite
sporangium of Peronospora trifoliorum parasitises live Lotus pedunculatus

Foodplant / spot causer
mostly hypophyllous colony of Ramularia anamorph of Ramularia sphaeroidea causes spots on fading leaf of Lotus pedunculatus
Other: major host/prey

Foodplant / feeds on
larva of Sitona cambricus feeds on Lotus pedunculatus

Perennial, Herbs, Stems woody below, or from woody crown or caudex, Plants with rhizomes or suckers, Nodules present, Stems erect or ascending, Stems less than 1 m tall, Stems 1-2 m tall, Stems solid, Stems or young twigs glabrous or sparsely glabrate, Stems or young twigs sparsely to densely hairy, Stem hairs hispid to villous, Leaves alternate, Leaves petiolate, Stipules conspicuous, Stipules green, triangulate to lanceolate or foliaceous, Stipules persistent, Stipules free, Stipules reduced to glands, Leaves compound, Leaves pinnately 3-foliolate, Leaves odd pinnate, Leaf or leaflet margins entire, Leaflets opposite, Leaflets 3, Leaflets 5-9, Leaves glabrous or nearly so, Inflorescence umbel-like or subumbellate, Inflorescence axillary, Bracts conspicuously present, Flowers zygomorphic, Calyx 5-lobed, Calyx hairy, Petals separate, Corolla papilionaceous, Petals clawed, Petals orange or yellow, Petals bicolored or with red, purple or yellow streaks or spots, Banner petal ovoid or obovate, Wing petals narrow, oblanceolate to oblong, Wing tips obtuse or rounded, Keel tips obtuse or rounded, not beaked, Stamens 9-10, Stamens or anthers dimorphic, alternating large and small, Stamens diadelphous, 9 united, 1 free, Filaments glabrous, Style teret e, Style persistent in fruit, Fruit a legume, Fruit unilocular, Fruit freely dehiscent, Fruit elongate, straight, Fruit or valves persistent on stem, Fruit coriaceous or becoming woody, Fruit exserted from calyx, Fruit internally septate between the seeds, Valves twisting or coiling after dehiscence, Fruit glabrous or glabrate, Fruit 11-many seeded, Seeds reniform, Seed surface smooth, Seeds olive, brown, or black.

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 20–80 cm (8–30 in) tall, with leaflets 10–25 mm (0.4–1 in) long and 10–20 mm (0.4–0.8 in) broad. Five to twelve golden-yellow flowers 10–18 mm (0.4–0.7 in) 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.

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.

Lotus pedunculatus is also a host plant for ovipositioning of the wood white butterfly, Leptidea sinapis.