Erodium trifolium (Cav.) Cav. (syn.: E. hymenodes L’Hérit., Geranium trifolium Cav.) (N Afr.) – An exceptional escape from cultivation. A small colony with 10-20 plants was discovered on an old quay wall in the city of Ghent in 2017. These plants are flowering from early in the season (April or earlier) and produce lots of fruits; they may have been present since several years already and look more or less established.
This species is probably rare as an ornamental and exceptionally recorded as an escape from cultivation in Europe. Similar records are available from the Netherlands where E. trifolium has been recorded in urban habitats in Amsterdam and Breda, at least between 2012 and 2014 (https://waarneming.nl/soort/view/442362).
Erodium trifolium is very similar to the Turkish endemic E. pelargoniiflorum Boiss. & Heldr. and both are often confused in the horticultural trade (Yeo 1982, Yeo 1997, Jäger & al. 2008). The latter has distinctly mucronate sepals (mucro up to 2 mm long) whereas sepals are emucronate in E. trifolium. These species also are reminiscent of some species of Pelargonium. They differ in having petals that are all alike in shape (the upper two usually larger and sepals spurred in Pelargonium).
Selected literature
Guittonneau G.-G. (2010) Aperçu sur la taxonomie, l’écologie et la phylogénie du genre Erodium L’Hér. dans le bassin méditerranéen. Available online at: http://www.tela-botanica.org/sites/alienplantsbelgium.bebotanique/fr/doc....
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Yeo P.F. (1982) Erodium pelargoniflorum and E. trifolium. Geraniaceae Group News 7: 8.
Yeo P.F. (1997) Erodium. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 50-56.