Taxonomic name: Melilotus alba (Medikus)
Synonyms: Melilotus alba Desr., Melilotus alba L., Melilotus albus Medik, Melilotus albus var. annuus H.S. Coe, Melilotus leucanthus W.D.J. Koch ex DC., Melilotus officinalis subsp. albus (Medik.) H. Ohashi and Tateishi
Common names: almengó blanc (Catalan-Spain), bai hua cao mu xi (Chinese), bokhara-clover (English-Australia, New Zealand), Bokharaklee (German), donnik belyi (Russian), fehér somkóró (Hungarian), heuin jeon dong ssa ri (Korean), hierba orejera (Spanish), honey clover, honey-lotus, hubam, hubam clover, hvid stenkløver (Dutch), hvit steinkløver (Norwegian), melilot, melilot blanc (Catalan-France), mélilot blanc (French), meliloto bianco (Italian), meliloto blanco (Spanish), meliloto-branco (Portuguese), Melilotos (Greek), mielcón (Spanish), mielga (Spanish), nostrzyk bialy (Polish), Shirobana shinagawa hagi (Japanese), trébol de olor blanco (Spanish-Argentina, Mexico), trébol oloroso (Spanish), tree clover, valkomesikkä (Finnish), Vit sötväppling (Swedish), Weisser honigklee (German), Weißer steinklee (German), white melilot, white millet, white sweetclover
Organism type: herb
Native to Asia, Europe, and northern Africa, Melilotus alba (commonly known as white sweet clover) was introduced to the United States and first recorded in 1739.
Melilotus alba is a biennial herb with pea-like flowers attached to small stalks of elongated stems (Cole, 1990). It is monocarpic, sweet scented, and has trifoliate leaves (Ekhardt, 1987). The leaves are alternate in arrangement and are 12.7-50.8mm (.5-2 in) (ANHP, 2006). The flowers are perfect spike-like racemes (Ekhardt, undated). The flowers are about 3-6.3mm (ANHP, 2006). The seed is ovoid, leathery, and wrinkled. M. alba is somewhat dehiscent. The plant is erect, brached and has a glabrous stem. M. alba is 1-3m high. The corolla is 4-5mm long and the fruit is 3-4mm and reticulate. This particular plant fowers in June-July. Flowering shoots can reach up to 1m (Ekhardt, undated). According to Frame (undated), the "seed pod has a reticulated, ridged coat which turns black with ripening and contains a single smooth kidney-shaped seed, about 2mm long, and brownish-yellow to brown."
agricultural areas, natural forests, range/grasslands, ruderal/disturbed
Melilotus alba grows in full sun or partial shade, but cannot tolerate dense shade. It prefers calcareous, loamy soils (Cole, 1990) with a pH from 5-8 (ANHP, 2006). M. alba can be found on roadsides, abandoned fields, railways, pastures, open natural communities and prairies (Cole, 1990). This species grows poorly on acidic soils (Uchytil, 1992).
Natural grasslands are degraded by Melilotus alba with the overtopping and shading of native species. Courmarin is produced by M. alba which is toxic to animals (ANHP, 2006). M. alba if not cured thoroughly can cause hemorrhaging in cattle. These hemorrhages are less common in horse and sheep. It is also known that white sweetclover causes bloating in livestock animals (Uchytil, 1992).
Young leaves of Melilotus alba have been used for tea, cooked greens, salads, and flavouring. Flowers can be pan roasted in order to make granola (LEC, 2005). M. alba is eaten by livestock. It is aslo grown for pasture and hay. White sweetclover is considered a good plant for soil restoration (Uchytil, 1992). Uchytil (1992) states that "white sweet clover provides good cover for small mammals, waterfowl, quail, and ring-necked pheasant." M. alba is regarded as an important plant for honey production (Uchytil, 1992).
Native range: Europe: Austria, Czech Republic, Slovakia, Germnay, Hungary, Poland, Estonia, Latvia, Lithuania, Greece, Italy, Cyprus, France, Spain, Bulgaria, Belarus, Republic of Moldova, Ukraine, Romania; Asia: Afghanistan, Iran, Iraq, Israel, Jordan, Lebanon, Turkey, Armenia, Azerbaijan, Russian Federation, Georgia, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan, China, Bhutan, India, Pakistan, Myanmar (Burma).
Known introduced range: North America: USA, Canada, Mexico; Australia.
Introduction pathways to new locations
Agriculture: M. alba is used for hay and pasture (Uchytil, 1992)
Other: Water helps to carry M. alba long distances (ANHP, 2006)
Local dispersal methods
On animals (local):
Physical:: Hand-pulling Melilotus alba is best done in the fall. In the spring the root crown must be removed when the ground is moist and before it begins to flower. Hand cutting stems just before flowering or on lower stems that dieback before flowering, usually does not resprout. Be sure to cut close to the ground (Cole, 1990). Prescribed burning is also used to contol white sweetclover (Uchytil, 1992). They must be burned in April of the first year which causes the seeds to germinate (Cole, 2006; DiTomaso et al, 2006). After the first burn seed germination is high (Uchytil, 1992) and there is a high density of M. alba (Curtis and Partch, 1948). In May of the second year when the plants are 1-2m high (Uchytil, 1992) they should be burned again which in turn kills emerging shoots before they seed. This procedure should be followed by two years of no burn (Cole, 1990).
Chemical: The herbicide 2, 4-D can be used to spot spray M. Alba. Herbicides are usually used for extremely disturbed sites (Cole,1990).
Biological: No biocontrol options have become available yet (Cole, 1990). Some considerations for biocontrol are the sweetclover weevil which damages the plant (Uchytil, 1992).
Melilotus alba has high self-fertility and cross fertility rates. It is pollinated by bees and wasps. Rainwater and runoff are the most important means of seed dispersal and the wind can carry the seeds several metres. Seed germination and seedling development occur during late March-April although sometimes it can last until fall (Ekhardt, 1987). M. alba requires at least 100 frost free days to reproduce (ANHP, 2006).
Nearly all energy in the early part of the growing season is put into top-growth. In late summer, however, the tops grow very little, while the roots grow dramatically. This is the "critical growth period" when plants allocate most energy to root growth." In the second year, the taproot may reach 120cm in depth. Along with this are 1-10 ascending flowering stems from 1-2.6m (Uchytil 1992).
Reviewed by: Expert review underway: Jeffery Conn (Jeff) Research Agronomist, Fairbanks, Alaska USA
Principal sources: Uchytil, Ronald J. 1992. Melilotus alba. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory [Producer].
Cole, M. 1990. Vegetation Management Guideline: White and Yellow Sweet Clover. Illinois Department of Conservation. 1(23).
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Friday, 3 August 2007