Sweet clover (Melilotus officinalis ) is a biennial plant that grows to heights of 2-4 ft (0.6-1.2 m) and produces small yellow flowers emitting a fragrance resembling that of hay or vanilla. It is a member of the legume, or Leguminosae, family. During its first year of growth, most of its energy goes into developing its root system. In the second year it flowers between May and September, sets its seeds, and dies. Its seeds may remain viable for over 30 years. The plant is also called hart's tree, hay flower, king's clover, melilot, sweet lucerne, or wild laburnum. Sweet clover grows in North America, Europe, Australia, and the temperate regions of Asia. In the early 1900s, sweet clover was grown for forage and to build up the soil, since its roots help to keep nitrogen in the soil. In the twenty-first century it is used to support honey production. In some agricultural areas of the United States, however, sweet clover is now considered a nuisance because it spreads rapidly and can take over open fields or prairies.
Sweet clover is valued for its medicinal uses because the flower contains coumarinic acids. Coumarin is the active ingredient in prescription anticoagulants (blood-thinning medications). Its presence in sweet clover allows it to reduce inflammation and swelling by increasing the flow of blood between the heart and the veins. As an herbal remedy, sweet clover is used in the treatment of bruises, hemorrhoids , and varicose veins . Its wound-healing properties have been confirmed in tests conducted on animals.
Taken internally as a tea or as a tisane, sweet clover relieves discomfort in the legs, particularly night cramps, itching , and swelling. The herb also supports the traditional medical treatments of vein inflammation, blood clots , and congestion of the lymph nodes. Applied externally as a poultice, sweet clover speeds the healing of bruises and eases the swelling of hemorrhoids.
Commercial preparations of sweet clover are available as dried crushed herb, as ointments, and as suppositories.
To prepare a sweet clover infusion, boiling water is poured over 1-2 tsp of the crushed flowers and stems. The infusion is allowed to steep for 5-10 minutes, then strained into a cup. For the treatment of varicose veins, 2-3 cups per day is recommended.
To prepare as a poultice, the crushed herb is mixed with a small amount of boiling water, then spread on a soft cloth. The cloth is applied to the affected area until the cloth is cold. The poultice is applied as needed.
The sale of herbal products is not regulated in the United States. They are sold as dietary supplements without proof of safety or a standard of quality control. In addition, the lack of comprehensive scientific research leaves the consumer without a standard to follow. There-fore, persons interested in using sweet clover or any other herbal remedy should always consult a physician or pharmacist before beginning a program of herbal therapy.
Long-term ingestion of high doses of sweet clover can cause headache and stupor. In isolated cases, temporary liver damage can result. These side effects disappear when the treatment is halted.
Although sweet clover does not have any identified interactions, prescription drugs containing coumarin have been known to interact adversely with other prescription drugs, especially blood thinners, aspirin, and heart medications. Persons taking prescription drugs of any type should check with their physicians before begining a regimen of sweet clover.
Coumarin can also cause birth defects and bleeding in the fetus. Therefore, the use of sweet clover should be avoided during pregnancy .
PDR for Herbal Medicines. Montvale, NJ: Medical Economics Company, 1998.