Berberis aquifolium Pursh (syn.: Mahonia aquifolium (Pursh) Nutt.) (incl. hybrids with B. repens Lindl. and B. pinnata Lag.) (N-Am.) – Commonly planted in public and private gardens, waysides,… First collected in 1906 in Lambermont but possibly not wild. Subsequently recorded in Fraipont (1921) and Comblain-au-Pont (from 1940’s onwards), twice more or less naturalised in nature-like habitats (rocky, wooded slopes). Little later and in identical habitats found in Yvoir (rochers de Champalle) and near Namur (Rochers des Grands Malades). In the past decades much extending and now more or less widespread in many parts of Flanders (Verloove 2002, 2006) and Wallonia. Highest densities seem to appear near large cities (Antwerpen, Brussel, Gent) and in coastal dunes, especially between Adinkerke and Nieuwpoort. Berberis aquifolium occupies a wide range of habitats, man-made as well as natural ones: urban waste land, disused industrial- and railway yards, along railway tracks and is also frequently found on old walls. Furthermore recorded in coastal seadunes (under shrubs, often along with native Hippophae rhamnoides) and on rocky, wooded slopes (especially in Wallonia; see also Wyzen 2008). Berberis aquifolium usually requires rather dry, shady places, often on calcareous soils.
Berberis aquifolium is a recently naturalised alien. It was, for instance, not yet included by van Rompaey & Delvosalle (1979). By now, after few decades, it has become an invasive environmental weed in some coastal dunes and perhaps elsewhere in natural habitats (e.g. Adriaens & al. 2019). Additional information on the invasive behaviour of Berberis aquifolium in Belgium is available at: http://ias.biodiversity.be/species/show/74.
The exact identity of the naturalised and invasive populations is uncertain. According to Jäger & Werner (2005) most populations probably belong to hybrids with Berberis pinnata (B. xwagneri Hort. ex Koehne; syn.: Mahonia xwagneri (Jouin) Rehder) and B. repens (B. xdecumbens (Stace) Verloove et Lambinon, Mahonia xdecumbens Stace) (Verloove & Lambinon 2011). Recent genetic research on invasive Central-European populations (Ross & al. 2008, Ross & Auge 2008) confirms the presence of genes of these related species. Indeed, genuine Berberis aquifolium is an erect, non-suckering shrub with usually 5-7 leaflets. Naturalised populations in Belgium (and elsewhere in parts of Europe) are extensively suckering and often have leaves with more numerous leaflets. The suckering habit obviously suggests introgression from Berberis repens. This hybrid probably is the most commonly naturalised plant in Belgium. In some coastal dunes (possibly elsewhere too), for instance in Noordduinen in Koksijde and Koningsbos in Knokke, plants with up to 13 leaflets were recently recorded. Such plants apparently are hybrids with Berberis pinnata.
Several related species are cultivated and might also occur as escapes (see for instance Taylor & Knees 1989, Roloff & Bärtels 2006). Adolphi (2001) reported about the escape of Berberis bealei Fort. (syn.: Mahonia bealei (Fort.) Carr.) in Germany.
Berberis aquifolium
Berberis x wagneri
Selected literature
Adolphi K. (1995) Neophytische Kultur- und Anbaupflanzen als Kulturflüchtlinge des Rheinlandes. Nardus 2: 272 p.
Adolphi K. (2001) In jüngster Zeit entdeckte Neophyten und Überlegungen über ihre mögliche Einbürgerung. Braunschweiger Geobotanische Arbeiten 8: 15-25.
Adriaens T., Verschelde P., Cartuyvels E., D’hondt B., Vercruysse E., van Gompel W., Dewulf E. & Provoost S. (2019) A preliminary field trial to compare control techniques for invasive Berberis aquifolium in Belgium coastal dunes. NeoBiota 53: 41-60. [available online at: https://neobiota.pensoft.net/article/38183/]
Houtman R.T., Kraan K.J. & Kromhout W.H. (2004) Mahonia aquifolium, M. repens & M. xwagneri en hybriden - sortimentsonderzoek en keuringsrapport. Dendroflora 41: 42-71.
Jäger E.J. & Werner K. (2005) Exkursionsflora von Deutschland. Band 4. Gefässpflanzen: Kritischer Band. Spektrum Akademischer Verlag, München: 980 p.
Junghans Th. (2016) Zur Ausbreitung wärmeliebender und immergrüner Adventivgehölze im Kontext der Klimaerwärmung. Mitt. Badischen Landesvereins Naturkunde Naturschutz e.V. 22(1): 85-104.
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Ross C.A. & Auge H. (2008) Invasive Mahonia plants outgrow their native relatives. Plant Ecology 199(1): 21-31.
Ross C.A., Auge H. & Durka W. (2008) Genetic relationships among three native North-American Mahonia species, invasive Mahonia populations from Europe, and commercial cultivars. Plant Syst. Evol. 275: 219-229.
Sperber H.H. (2003) Zur Ausbreitung neophytischer Sträucher im mittleren Rheinland-Pfalz, vornehmlich Mahonie (Mahonia aquifolium (Pursh) Nutt.). Mainzer naturwiss. Archiv 41: 133-147.
Taylor N.P. & Knees S.G. (1989) Mahonia. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 3. Cambridge University Press, Cambridge: 371-373.
Van Rompaey E. & Delvosalle L. (1979) Atlas de la flore belge et luxembourgeoise. Ptéridophytes et Spermatophytes (2ième éd.). Jardin Botanique National de Belgique, Meise: 1542 cartes.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Verloove F. (2006) Mahonia aquifolium. 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: 572.
Verloove F. & Lambinon J. (2011) The non-native vascular flora of Belgium: new combinations and a new variety. New Journ. Bot. 1(1): 38-42.
Wyzen F. (2008) Le cours inférieur de la Chawresse à Méry-Tilff. Adoxa 58: 33-35.