Blackdisk Medick

In Great Britain and/or Ireland:
Foodplant / parasite
Erysiphe pisi var. pisi parasitises Medicago orbicularis

Annual, stem 10-45 cm, glabrous to subglabrous. Leaflets 7-18 mm long, obovate to cuneate, mostly retuse, dentate; stipules laciniate. Inflorescence a 1-5-flowered peduncled raceme, peduncle longer than the petiole. Calyx c. 3.5 mm long, teeth almost equal to the tube. Corolla about twice the calyx, yellow. Fruit discoid, with 3-7 coils, 4-5 mm broad, glabrous.

Distribution: Pakistan [N.W.F. Province, Baluchistan (Burkill, List Fl.Pl. Baluch. 1909)]; Iran, Iraq, Palestine, Lebanon, Syria; Egypt, Turkey, Greece, Russia (Caucasus), S. Europe, Tunisia, Algeria; Morocco.

Fl.Per.: March-April.

Annual, Herbs, Taproot present, Nodules present, Stems prostrate, trailing, or mat forming, Stems less than 1 m tall, Stems solid, Stems or young twigs glabrous or sparsely glabrate, Stems or young twigs sparsely to densely hairy, Leaves alternate, Leaves petiolate, Stipules conspicuous, Stipules green, triangulate to lanceolate or foliaceous, Stipules persistent, Stipules free, Stipules toothed or laciniate, Leaves compound, Leaves pinnately 3-foliolate, Leaves odd pinnate, Leaflets dentate or denticulate, Leaflets opposite, Leaflets 3, Leaves glabrous or nearly so, Leaves hairy on one or both surfaces, Flowers in axillary clusters or few-floweredracem es, 2-6 flowers, Inflorescences racemes, Inflorescence axillary, Flowers zygomorphic, Calyx 5-lobed, Calyx hairy, Petals separate, Corolla papilionaceous, Petals clawed, Petals orange or yellow, Banner petal ovoid or obovate, Wing petals narrow, oblanceolate to oblong, Wing petals auriculate, Wing tips obtuse or rounded, Keel tips obtuse or rounded, not beaked, Stamens 9-10, Stamens diadelphous, 9 united, 1 free, Filaments glabrous, Style terete, Fruit a legume, Fruit unilocular, Fruit indehiscent, Fruit spirally coiled or contorted, Fruit exserted from calyx, Fruit hairy, Fruit gland-dotted or with gland-tipped hairs, Fruit 2-seeded, Fruit 3-10 seeded, Seeds reniform, Seed surface smooth, Seeds olive, brown, or black.

Medicago orbicularis is a plant species found throughout the Mediterranean basin and along the European Black Sea coast. It forms a symbiotic relationship with the bacterium Sinorhizobium medicae, which is capable of nitrogen fixation. Common names include blackdisk medick, button clover, button medick, and round-fruited medick.