Campanula fenestrellata Feer (syn.: C. garganica Ten. subsp. fenestrellata (Feer) Hayek) (SC-Eur.) – A very rare escape from cultivation. Known for many years and at least since 2001 from a brick quay wall (Zeekanaal) in Humbeek (Ronse 2006) where it recently disappeared after infrastructural works. In 2015 also seen in an urban area in Brussels and on an old wall in Durbuy. Possibly overlooked elsewhere.
Campanula fenestrellata belongs to a complex of closely related species, mostly native to Italy and former Yugoslavia (further including, among others, C. portenschlagiana and C. poscharskyana). They are insufficiently known in Belgium and their identity is often further complicated due to artificial crossings, selection,… Garden plants rarely perfectly match with their native ancestors (for instance in hairyness, dimensions,…).
Although Campanula fenestrellata and C. garganica are sometimes considered to be conspecific (e.g. E+M Plantbase), molecular studies seem to indicate that both are only remotely related (Bogdanovic & al. 2014).
Very typical features of Campanula fenestrellata (and C. garganica s.l.) are its long exserted style and relatively tiny corollas. C. garganica and C. fenestrellata only seem to differ on pollen colour; they are perhaps better synonymized (see also Euro+Med Plantbase).
Selected literature:
Bogdanović S., Brullo S., Rešetnik I., Satovic Z. & Liber Z. (2014) Campanula teutana, a new isophyllous Campanula (Campanulaceae) from the Adriatic region. Phytotaxa 162: 1-17. [available online at: https://www.researchgate.net/publication/260754165_Campanula_teutana_a_n...
Dunkel F.-G. (2006) Neues oder Bemerkenswertes zur Flora Bayerns – Achillea roseoalba, Orobanche amethystea und andere Funde. Ber. Bayer. Bot. Ges. 76: 151-168.
Ronse A. (2006) Campanula fenestrellata: eerste waarneming van verwildering in België. Dumortiera 90: 10-12. [available online at: http://alienplantsbelgium.be/sites/alienplantsbelgium.be/files/dum90p10....