Dryopteris cycadina
Dryopteris cycadina (Franch. et Sav.) C. Chr. (temp. As.) – An exceptional escape from cultivation. A single individual was found in 2006 on a basement wall in the city of Gent. It apparently did not survive the cold winter of 2009-2010. In 2016, also in Gent (Mariakerke), found near a ditch at the edge of young woodland and in 2017, still in Gent, another individual in a basement.
Dryopteris cycadina is part of a taxonomically difficult group, the Dryopteris atrata (Kunze) Ching-complex. Such plants are distinct in having once pinnate fronds and narrow, dark scales on stipe and rachis (subgenus Dryopteris, section Hirtipedes; Fraser-Jenkins 1986). The horticultural plant appears to be Dryopteris cycadina. Formerly the names Dryopteris atrata (see Joe 1963) and D. hirtipes (Blume) Kuntze were misapplied to it. These taxa, among some others (see Fraser-Jenkins 1989), are easily confused and can be distinguished as follows:
D. hirtipes (incl. D. atrata): stipe long, pinnae broader and widely spaced;
D. cycadina: stipe short, pinnae narrower and more closely spaced.
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Selected literature
Edgington J.A. (2005) Exotic ferns on London walls. BSBI News 100: 42-44.
Fraser-Jenkins C.R. (1986) A classification of the genus Dryopteris (Pteridophyta: Dryopteridaceae). Bull. Br. Mus. Nat. Hist. (Bot.) 14: 183-218.
Fraser-Jenkins C.R. (1989) A monograph of Dryopteris (Pteridophyta: Dryopteridaceae) in the Indian subcontinent. Bull. Br. Mus. Nat. Hist. (Bot.) 18: 323-477.
Joe B. (1963) Species of Dryopteris cultivated in California. Baileya 11: 117-130.
Verloove F., van der Ham R. & Denters T. (2007) Exotische muurvarens in België en Nederland. Dumortiera 92: 1-16.