Melilotus indicus (L.) All. (Medit., W and C-As., Macaronesia) – A rather frequent but probably always ephemeral alien. Known since ca. 1851. Most early records (19th century) are from arable land. Later also recorded on waste land, often near grain mills. Regularly observed as a wool alien in the valley of river Vesdre between 1887 and 1970 (see also Visé 1942, Visé 1958). In the past decades still frequently seen and nearly always associated with grain importation (including birdseed). As such, recorded in port areas near grain mills (unloading quays, under grain conveyors, near railway tracks), by road verges, on dumps or in gardens (from birdseed). It is still regularly seen on gravelly river banks, for instance of river Maas in Limburg (and even claimed to be naturalised; see Dijkstra 2012). Melilotus indicus is, along with Medicago polymorpha, a very characteristic alien on demolition sites (emerging from long-buried seed banks; see Verloove & Heyneman 2012). Finally, it also is a regular introduction in plant containers in nurseries, mainly with olive trees (Hoste & al. 2009).
Melilotus indicus is by far the commonest of the small-flowered species of the genus. However, it should not be confused with Melilotus sulcatus. Both are often found in similar habitats and are best distinguished on fruit characters. In the latter stipules often tend to be more deeply dentate but this surely is not always a reliable feature. In the field Melilotus officinalis and M. indicus are usually easily separated (dimensions of stem and corollas, pods, etc.). However, in the herbarium, when only upper parts of the plant are collected, identification is often complicated since both species potentially have corollas that more or less overlap in length (especially when dry). Therefore, corolla measurements are best taken when fresh. If ripe fruits are available, then both are easily distinguished on the sole basis of seed ornamentation: seeds are minutely tuberculate in Melilotus indicus and smooth in M. officinalis.
Dijkstra K. (2012) Wilde planten in Nederland en België. Available online at: http://wilde-planten.nl/kleine%20honingklaver.htm.
Hoste I., Verloove F., Nagels C., Andriessen L. & Lambinon J. (2009) De adventievenflora van in België ingevoerde mediterrane containerplanten. Dumortiera 97: 1-16.
Trzcinska-Tacik H. (1967) Melilotus indica (L.) All. i M. wolgicus Poir. w Polsce., Fragm. Florist. Geobot. 13: 351-355.
Verloove F. (1992) De adventievenflora van de Roeselaarse binnenhaven (West-Vlaanderen, België). Dumortiera 51: 22-29.
Verloove F. & Heyneman G. (2012) Merkwaardige plantencollecties van twee antropogene zaadbanken in Gent (Oost-Vlaanderen, België). Dumortiera 100: 19-24.
Verloove F. & Vandenberghe C. (1993) Nieuwe en interessante graanadventieven voor de Noordvlaamse en Noordfranse flora, hoofdzakelijk in 1992. Dumortiera 53-54: 35-57.
Visé A. (1942) La flore adventice de la région de Verviers. Lejeunia 6: 99-119.
Visé A. (1958) Florule adventice de la vallée de la Vesdre. Bull. Soc. Roy. Bot. Belg. 90: 287-305.