Melilotus officinalis Lam. (Euras.) – A commonly and widely naturalised alien. Already recorded prior to 1800 in Belgium and residence status very uncertain. Archaeophytic instead of neophytic status cannot be excluded. In Belgium similarly distributed as Melilotus albus (see above) but probably slightly decreasing lately (Ronse 2006c). Melilotus officinalis also shares the same habitats and both are often found together.
In the herbarium confusion is possible with Melilotus albus and M. indicus, see under these species. However, this is even more likely with Melilotus altissimus. The latter has darker corollas (golden to almost orange-yellow) but this is hardly detectable when dry. They are best separated on fruit and ovary characters (see key).
The very similar but Asian Melilotus suaveolens Ledeb. (syn.: M. graveolens Bunge) might have been overlooked. Some races of it are cultivated and might represent a hybrid of Melilotus albus and M. officinalis (see Stevenson 1969 for their distinction). Similarly, the Mediterranean Melilotus elegans Salzm. might have been confused with M. officinalis.
Ronse A. (2006c) Melilotus officinalis. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 584.
Stevenson G.A. (1969) An agronomic and taxonomic overview of the genus Melilotus Mill. Can. J. Plant Sc. 49: 1-20. [available on line at: http://pubs.aic.ca/doi/pdf/10.4141/cjps69-001]
Turkington R.A.., Cavers P.B. & Rempel E. (1978) The biology of Canadian weeds: 29. Melilotus alba Desr. and M. officinalis (L. ) Lam. Canad. J. Pl. Sci. 58(2): 523-537. [available online at: http://pubs.aic.ca/doi/pdf/10.4141/cjps78-078]