Ammi majus L. (Medit.) – A rather frequent but usually ephemeral alien. Apparently first recorded in 1813 (Durand 1899). In the second half of the 19th century a local weed of agricultural land (e.g. oat, alfalfa, clover) and possibly more or less naturalized for some time. Furthermore known from numerous, very widely scattered locations. At present chiefly associated with grain importation and most often found along road verges, in port areas, waste land, canal banks, etc. Ammi majus also occurs where birds are fed (e.g. De Ridder 1986). Sometimes temporarily persistent near grain mills but not becoming fully naturalized (yet). However, Ammi majus seems to increase recently as an agricultural weed (for instance in northern France but also in parts of Belgium). More or less stable populations seem to be present in the wide surroundings of Kortrijk and in the valley of river Maas in Limburg (see here for an up-to-date distribution map for Belgium: http://waarnemingen.be/soort/maps/6411?from=1900-05-08&to=2014-05-08&count_ex=0&only_valid=0&grid=5000&kwart=0&st=&second_specie=); a future, wider naturalization seems likely.
Typical plants of Ammi majus are readily distinguished from A. visnaga (even in the absence of the typical infrutescence of the latter) by lower leaf segments that are much broader than the upper ones (all more or less alike in A. visnaga). However, var. glaucifolium (L.) Mérat has narrowly divided lower leaf segments and is hardly distinguishable. Such plants regularly occur in Belgium as well.
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Selected literature:
Cappelletti E.M. (1979) Differential microcharacters of epicarp surfaces of Ammi visnaga and Ammi majus. Pl. Med. 37: 143-150.
De Ridder M. (1986) Adventieven en vogelzaad. Dumortiera 34-35: 143-145.
Durand T. (1899) Phanérogames. In: De Wildeman E. & Durand T., Prodrome de la flore belge. A. Castaigne Editeur, Bruxelles: 1112 p.
Follak S. (2015) Notizen zum Vorkommen von Ammi majus (Große Knorpelmöhre) in Österreich. Stapfia 103: 115-119. [available online at: http://www.zobodat.at/pdf/STAPFIA_0103_0115-0119.pdf]
Garve E. (2003) Zwei Äcker voller Ammi. Floristische Notizen aus der Lüneburger Heide 11: 2-6.
Robbrecht E. & Jongepier J.-W. (1986) Floristische waarnemingen in de kanaalzone Gent-Terneuzen (België, Oost-Vlaanderen & Nederland, Zeeuws-Vlaanderen), vooral van 1981 tot 1985. Dumortiera 36: 6-21.
Ronse A. (2019) Ammi majus (Apiaceae) in België ingeburgerd als akkeronkruid. Dumortiera 114: 18-25. [available online at: http://db.plantentuinmeise.be/DUMORTIERA/DUM_114/Dum_114_18-25_Ammi_maju...
Saintenoy-Simon J., Godefroid S. & Verhelpen B. (1995) Groupe Flore Bruxelloise. Notes floristiques relatives à la Région de Bruxelles-Capitale (1991-1993). Adoxa 6-7: 27-37.
Verloove F. & Vandenberghe C. (1993) Nieuwe en interessante graanadventieven voor de Noordvlaamse en Noordfranse flora, hoofdzakelijk in 1992. Dumortiera 53-54: 35-57. [available online at: http://alienplantsbelgium.be/sites/alienplantsbelgium.be/files/dum53-54p35.pdf]
Wurzell B.S. (1994) Year of the Bullwort. B.S.B.I. News 66: 32. [available online at: http://archive.bsbi.org.uk/BSBINews66.pdf]