Ribbed Melilot (Melilotus officinalis) also known as sweet clover can be an annual or biennial plant, and can grow to be almost 2m high at maturity. Leaves alternate on the stem and possess three leaflets. Yellow flowers bloom in spring and summer and produce fruit in pods typically containing one seed. Seeds can be viable for up to 30 years. Originally a fodder plant in the 16th century, Ribbed Melilot was also used by herbalists as the juice of the plant was reputed to help with eye problems.
This plant is much loved by bees, hoverflies and moths as it has an abundance of nectar.
Sweet clover contains coumarin that converts to dicoumarol, which is a powerful anticoagulant toxin, when the plant becomes moldy. This can lead to bleeding diseases (internal hemorrhaging) and death in cattle. Consequently, hay containing the plant must be properly dried and cured, especially in wet environments.
Before World War II, before agricultural fertilizers were widely used, the plant was commonly used as a cover crop to increase nitrogen content and improve subsoil water capacity in poor soils. It is the most drought-tolerant of the commercially available legumes.
Sweet clover is a major source of nectar for domestic honey bees as hives near sweet clover can yield up to 200 pounds of honey in a year.