Sour clover (Melilotus indicus (L.) All.) is an erect annual forage legume, up to 50-80 cm high. It has a deep taproot, down to a depth of 1.2 m. The stems are branched, glabrous or sparsely pubescent. The foliage is heavy, somewhat succulent with high water requirements. The leaves are alternate, trifoliolate, with oblong to obovate leaflets 0.8-2.5 cm long x 2-9 mm broad. Inflorescences are racemose, apically or axillary, borne on 1-3 cm long peduncles. The flowers (10-16 per raceme) are papillonaceous, sweet smelling, sparsely pubescent and yellow in colour. The olive-green fruits are one-seeded, reticulately veined, 1.5-4 mm long, indehiscent pods. The seeds resemble those of alfafa and are ovoid, glabrous, yellow-brown, about 2 mm in length. They may be hard-seeded (about 5 to 20%) and thus will not germinate in the first year (UC SAREP, 2006; Wilken et al., 1998; Arora et al., 1997)
Sour clover is a multipurpose plant. It is a valuable green manure or cover crop, and can be used as fodder. In California, in the 1920’s, it was one of the leading winter cover crops and was particularly cultivated in citrus orchards (UC SAREP, 2006). In India, it is valued as a drought resistant legume forage (NDDB, 2012).