Ficus carica L. (Medit.?, SW-As.) – A rare but increasing food refuse alien. The first Belgian records are exclusively from thermophilous, rocky substrates in Wallonia. It was known since the 1930’s from the quays along river Vesdre near Verviers: five individuals were said to be very persistent and considered locally “naturalized”, although their presence was not confirmed posterior to 1957. Elsewhere in this river valley also recorded in 1990 near Chênée. Furthermore seen in 1948 along river Meuse near Visé. Known from a quarry in Comblain-au-Pont (Géromont) where it was possibly introduced intentionally by North African immigrants around 1910-1920 (recently confirmed from there). From the 1950’s onwards also regularly found on dumps (from kitchen waste). At present chiefly confined to urban habitats (quays, basement walls, etc.) and known from numerous cities. Initially it was chiefly confined to the larger cities like Antwerpen, Brussel, Gent, Leuven, etc. but nowadays it is also found in smaller cities and villages. An up-to-date overview of records is provided here: https://waarnemingen.be/soort/view/6791.
Ficus carica apparently easily germinates from thrown away pits. These refer to commercial, seed-bearing figs introduced from the south (see below). It behaves analogously in most neighboring countries, see for instance Adolphi (1995) for an overview for Germany or Dickson & Dickson (1996) for the British Isles.
The exact residence status of Ficus carica in Belgium is unclear. Each Ficus species needs a specific pollinating wasp in order to reproduce and spread (Ramirez 1970). The pollinator wasp for F. carica, Blastophaga psenses (L.), is absent from Belgium. As a result, F. carica is not reproducing sexually here and only parthenocarpic varieties ripen figs, i.e. without pollination. This means that the species is unable to reproduce sexually but it surely persists very well. Plants/clones in a quarry in Géromont are known to be present since about a century and some of the oldest individuals in the city of Ghent probably persist since the 1980’s and by now have reached gigantic dimensions. However, it is unlikely that Ficus carica will naturalize here, unless its pollinator would be introduced (or spontaneously reach Belgium) as well. Keil & al. (2010) demonstrated that Ficus carica rather easily survived extreme low temperatures in Central Europe, at least if local environmental conditions are suitable (micro-climate). However, there as well, a genuine naturalization in a near future appeared to be unlikely.
Selected literature:
Adolphi K. (1995) Neophytische Kultur- und Anbaupflanzen als Kulturflüchtlinge des Rheinlandes. Nardus 2: 272 p.
Allen C. & Hobson C. (1995) Figs in the north Midlands and northern England. B.S.B.I. News 69: 59. [available online at: https://archive.bsbi.org.uk/BSBINews69.pdf]
Dickson J. (1990) The only large wild fig tree in Scotland? B.S.E. News 55: 6-7.
Dickson J.B. (1996) Glasgow wild Fig tree's demise. B.S.S. News 67: 11-12.
Dickson J.H. & Dickson C. (1996) Ancient and modern occurrences of Common Fig (Ficus carica L.) in the British Isles. Quatern. Sci. Rev. 15: 623-633.
Gilbert O.L. & Pearman M.C. (1988) Wild figs by the Don. Sorby Rec. 25: 31-33.
Keil P., Fuchs R., Buch C. & Schmitt R. (2010) Echte Feigen (Ficus carica, Moraceae) in Mülheim an der Ruhr nach dem Kältewinter 2008/2009. Decheniana 163: 61-70. [available online at: https://www.bio-diverse.de/?p=968]
Mazomeit J. (2008) Verwilderungen des Feigenbaums (Ficus carica) in der Kurpfalz. Pollichia-Kurier 24(2): 18-20. [available online at: https://www.pollichia.de/index.php/download/category/36-arbeitskreis-bot...
Mazomeit J. (2016) Über verwilderte Feigen (Ficus carica) an Fließgewässern im Oberrheingraben. Fauna und Flora in Rheinland-Pfalz: Zeitschrift für Naturschutz 13(2): 597-600.
Ramirez B.W. (1970) Host specificity of fig wasps (Agaonidae). Evol. 24: 680-691.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Wirth T., Fazekas I., Schmidt Cs. & Csiky J. (2020) Spreading to north: naturalisation of Ficus carica (Moraceae) in Hungary. Acta Botanica Hungarica 62(1-2): 187-201. [available online at: https://akjournals.com/view/journals/034/62/1-2/article-p187.xml]