''Melilotus officinalis'', known as sweet yellow clover, yellow melilot, ribbed melilot and common melilot, is a species of legume native to

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...

and introduced in North America,

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

, and Australia.

Description

''Melilotus officinalis'' can be an annual or biennial plant, and is high at maturity. Leaves

alternate Alternative or alternate may refer to: Arts, entertainment and media * Alternative (''Kamen Rider''), a character in the Japanese TV series ''Kamen Rider Ryuki'' * ''The Alternative'' (film), a 1978 Australian television film * ''The Alternative ...

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. Plants have large taproots and tend to grow in groups. Plants have a characteristic sweet odor.

Habitat

''M. officinalis'' is native to Europe and Asia and has been introduced to North America as a forage crop. It commonly grows in

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an ad ...

loamy and clay soils with a pH above 6.5 and can tolerate cold temperatures and drought; it does not tolerate standing water or acidic soils, with a pH of 5.5 as the plant's lowest limit. Common places where it can be found include open disturbed land, prairies, and savannahs, and it grows in full or partial sunlight. It is an invasive species in areas where it has been introduced, especially in open grasslands and woodlands where it shades and outcompetes native plant species.

Toxicology

Sweet clover contains coumarin that converts to

dicoumarol Dicoumarol ( INN) or dicumarol (USAN) is a naturally occurring anticoagulant drug that depletes stores of vitamin K (similar to warfarin, a drug that dicoumarol inspired). It is also used in biochemical experiments as an inhibitor of reductases. ...

, 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.

Uses

The seeds are eaten by game birds, including grouse. Sweetclover can be used as pasture or livestock feed when properly cured. It is most palatable in spring and early summer, but livestock may need time to adjust to the bitter taste of

coumarin Coumarin () or 2''H''-chromen-2-one is an aromatic organic chemical compound with formula . Its molecule can be described as a benzene molecule with two adjacent hydrogen atoms replaced by a lactone-like chain , forming a second six-membered h ...

in the plant. Prior to

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

, before the common use of commercial agricultural fertilizers, 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 bee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...

s as hives near sweetclover can yield up to 200 pounds of honey in a year. Sweetclover has been used as a

phytoremediation Phytoremediation technologies use living plants to clean up soil, air and water contaminated with hazardous contaminants. It is defined as "the use of green plants and the associated microorganisms, along with proper soil amendments and agronom ...

—phytodegradation plant for treatment of soils contaminated with dioxins.Sandia National Labs: SSFL Report; pg.10
. accessed 6.12.2012 In the chemical industry, dicoumarol is extracted from the plant to produce

rodenticide Rodenticides are chemicals made and sold for the purpose of killing rodents. While commonly referred to as "rat poison", rodenticides are also used to kill mice, squirrels, woodchucks, chipmunks, porcupines, nutria, beavers, and voles. Despi ...

Management

When ''M. officinalis'' is invasive, it can be managed by mulching, hand-pulling, mowing, or herbicide applications such (e.g., 2,4-D) before flowering. Prescribed burns in late fall or early spring followed by another burn in late spring can reduce the number of plants before seed set.

References

{{Taxonbar, from=Q161160 Trifolieae Flora of Asia Flora of Europe Phytoremediation plants Medicinal plants