Melilotus species are eaten by the
larvae of some
Lepidoptera species, such as those of the genus
Coleophora, including
C. frischella and
C. trifolii. The plants have a sweet smell, which is due to the presence of
coumarin in the tissues. Coumarin, though responsible for the sweet smell of hay and
newly mowed grass, has a bitter taste, and, as such, possibly acts as a means for the plant to discourage consumption by animals. Some mould fungi (including
Penicillium, Aspergillus, Fusarium, and
Mucor) can convert coumarin into
dicoumarol, a toxic
anticoagulant. Consequently, dicoumarol may be found in decaying
Melilotus, and was the cause of the so-called "sweet-clover disease", identified in cattle in the 1920s. A few
cultivars have been developed with low coumarin content and are safer for forage and
silage. Some species are used as a
green manure, grown for a while and then ploughed into the soil to increase the soil nitrogen and organic matter content. It is especially valuable in heavy soils because of its deep rooting. However, it may fail if the soil is too acidic.
Unscarified seed is best sown in spring when the ground is not too dry; scarified seed is better sown in late fall or even in the snow, so it will germinate before competing weeds the following spring.
Melilotus siculus is notable for its high combined tolerance to salinity and waterlogging. As of 2019, the cultivar 'Neptune' has the highest tolerance and persistence under salinity among all pasture legumes, according to the Australian
Department of Primary Industries and Regional Development. The salt-tolerant symbiont
Ensifer medicae SRDI554 is recommended. ==References==