Polystichum acrostichoides (Michaux) Schott (N Am.) - An exceptional escape from or relic of cultivation. A small population with ca. 15 individuals was discovered in woodland in a private estate in Heks (Heers) in 2019.
Polystichum acrostichoides much resembles P. munitum and P. lonchitis in gross morphology. It is, however, unmistakable if fertile fronds are present.
According to Wagner (1993) this species is naturalized in Europe. We have no idea what might be the source of this statement. Although widely cultivated (e.g. Jäger & al. 2008), this species apparently has rarely been recorded outside of its native distribution range, if ever.
Selected literature
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.
Wagner D.H. (1993) Polystichum. In: Flora of North America Editorial Committee (ed.), Flora of North America, vol. 2: 290-299. Oxford University Press, New York-Oxford. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=126461]