Chaerophyllum bulbosum L. (C and E-Eur., SW-As.) – A very rare and probably ephemeral alien. First recorded in Vorst in 1873, later also between Melle and Laarne in 1924 in a damp grassland (escape from cultivation). Furthermore observed in the garden of J. Duvigneaud in Marchienne-au-Pont in 1987, apparently introduced unintentionally. More recently seen in Moerbeke (Heidebos) on waste land near a former local airport in 1997 (several tens but only one left in 1998 and now probably gone). In 2015 two individuals were observed on a talus slope near a grain mill in Moen. A claim from Wijgmaal in 1991 (Florabank) requires confirmation.
The very similar Chaerophyllum prescottii DC. (cf. Hämet-Ahti 1967, Fröberg 2010) might have been confused with C. bulbosum.
Fröberg L. (2010) Chaerophyllum. In: Jonsell B. & Karlsson T. (eds.), Flora Nordica, vol. 6. The Swedish Museum of Natural History, Stockholm: 199-206.
Hämet-Ahti L. (1967) Chaerophyllum bulbosum L. ssp. bulbosum and ssp. prescottii (DC.) Nyman in Finland. Ann. Bot. Fenn. 4: 417-421.
Passarge H. (1989) Zur Coenologie von Carduus crispus und Chaerophyllum bulbosum-Fluren. Hercynia N.F. 26: 102-115.