3. Ribes xnidigrolaria R. Bauer & A. Bauer (R. divaricatum x R. nigrum x R. uva-crispa) (Hort.) – A very rare escape from cultivation but probably increasing and/or overlooked. Regularly cultivated for its edible fruits and sometimes seen as a relic of cultivation. Since 2008 recorded on riverbanks (between granite blocks) in Flanders, probably birdsown or from washed-up rhizomes (Verloove 2011): first seen along river Leie near Wervik, subsequently also along river Schelde (at its junction with Ringvaart) near Melle (apparently well-established; confirmed in 2010). In 2010 furthermore discovered in grassland (former dump) along motorway E40 near Drongen (a single bush) and in 2015 in Balen. Possibly overlooked elsewhere. Ribes xnidigrolaria grows in nitrophilous, wet habitats.
Ribes xnidigrolaria, best known as Jostaberry, is an artificial, fertile hybrid of complex parentage (Bauer & Bauer 1989). In general habit and leaf shape it mostly resembles Ribes nigrum but corollas are greenish-purple and distinctly hairy (a character of R. divaricatum). Unlike Ribes divaricatum and R. uva-crispa, R. xnidigrolaria lacks thorns. This hybrid is sometimes erroneously referred to as Ribes xculverwellii MacFarlane. The latter is a nearly sterile hybrid of R. nigrum and R. uva-crispa. Despite its complex parentage Ribes xnidigrolaria is a fully fertile taxon and relatively easily escapes (see also Mang 1992, Weber 1995). It is surprisingly omitted in many horticultural or dendrological standard works (see for instance Tebbitt 1995, De Koning & al. 2000,…).
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Herbarium specimen Ribes x nidigrolaria
Selected literature
Bauer A. & Weber H.E. (1989) Ribes x nidigrolaria R. & A. Bauer und Fragaria x vescana R. & A. Bauer – Beschreibung zweier Hybridarten. Osnabrücker naturwiss. Mitt. 15: 49-58.
De Koning J., Van den Broek J.W., Van de Laar H.J. & Fortgens G. (2000) Nederlandse den drologie (13e druk). H. Veenman & zonen, Ede: 585 p.
Mang F.W.C. (1992) Zur Verwilderung der Jostabeere, Ribes x nidigrolaria R. et A. Bauer an zwei Standorten in Hamburg. Osnabrück. Naturwiss. Mitt. 17: 175-178.
Tebbitt M.C. (1995) Ribes. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 4. Cambridge University Press, Cambridge: 286-294.
Verloove F. (2011) Fraxinus pennsylvanica, Pterocarya fraxinifolia en andere opmerkelijke uitheemse rivierbegeleiders in België en NW-Frankrijk. Dumortiera 99: 1-10.
Weber H.E. (ed.) (1995) Grossulariaceae. In: Illustrierte Flora van Mitteleuropa, vol. 4(2A) (3th ed.). Blackwell Wissenschafts-Verlag, Berlin: 48-68.