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

legume A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock f ...

native to Eurasia and introduced in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, Africa, and

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Description

''Melilotus officinalis'' can be an annual or

biennial plant A biennial plant is a flowering plant that, generally in a temperate climate, takes two years to complete its biological life cycle. Life cycle In its first year, the biennal plant undergoes primary growth, during which its vegetative structures ...

, and is 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. 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 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 An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

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, which is a powerful

anticoagulant Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...

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 in the plant. Prior to World War II, 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 bees as hives near sweetclover can yield up to 200 pounds of honey in a year. Sweetclover has been used as a phytoremediation—phytodegradation plant for treatment of soils contaminated with

dioxin Dioxin may refer to: * 1,2-Dioxin or 1,4-Dioxin, two unsaturated heterocyclic 6-membered rings where two carbon atoms have been replaced by oxygen atoms, giving the molecular formula C4H4O2 *Dibenzo-1,4-dioxin, the parent compound also known as ...

s.Sandia National Labs: SSFL Report; pg.10
. accessed 6.12.2012 In the chemical industry, dicoumarol is extracted from the plant to produce rodenticides.

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