Cornish Biodiversity Network  -  Supporting Wildlife Recording

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Cornish Red Data (2009)

The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.

Thelypteris palustris - Marsh Fern

Range & Status

Native. Circumpolar Temperate fern. Scattered across southern Britain and Ireland. It

tends to be more frequent in the east.

Regional Distribution

Extremely rare; it was formerly known from one site in West Cornwall. In 1999 it was

discovered north of Castle-an-Dinas, just north of Goss Moor (SW96), last seen in 2002, and in 2003 was found near Morwenstow (SS21).

Habitat & Ecology

It appears to grow in base-rich mire communities. The site north of Castle-an-Dinas, was up until the 1950s an area of re-worked mine tailings, which have retained open areas where the fern was able to colonise. The Morwenstow site is a small relict area of wet coastal Culm Measures grassland.


The main threats are scrub invasion and drainage. The West Cornwall site was lost due to scrub encroachment.


The Castle-an-Dinas site is part of the Tregonetha Downs SSSI, which is currently being cattle grazed.

Click here to see Aphotoflora images by David Fenwick


I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.

The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.