West Highland Flora

Northern Buckler Fern


Dryopteris expansa

Previous name: Dryopteris assimilis.  Was at one time included in D dilatata.

Dryopteris expansa

Photo John Birks
Department of Biology, University of Bergen
Aug 1967 Beinn Udlaidh, Argyll

Rare, usually in rocky ground or woods.

Fronds c 30-100 cm.  Pinnae c 5-20 cm.  Sori 0.5-1 mm.

ID: Lowest pinna the most developed, as in the other Buckler Ferns, with the pinnule nearest the stem on the lower side of the lowest pinna particularly large and resembling a whole pinna from further up the blade.  Pinnules flat, not concave like those of D aemula nor convex like those of D dilatata usually are.  Scales at base of stalk mid-brown, with or without dark centres, not usually pale like those of D carthusiana, which has narrower fronds.

This fern can be very difficult to identify with certainty.  Look at all the fronds, and all the plants if there is a group of them, rather than puzzling over just one which may not be typical.

Other features: Fronds tend not to arch over as those of D dilatata do.  Pinnules are more deeply cut than in D dilatata and D carthusiana, with many of them cut almost to the midrib.  Fronds grow in tufts from a "crown" like those of D dilatata and unlike those of D carthusiana (which may form small semi-tufts but will have single fronds nearby)

 

Dryopteris expansa

Photo John Birks
Department of Biology, University of Bergen
Jun 1975 Caenlochan, Grampians

 

Dryopteris expansa

Photo John Birks
Department of Biology, University of Bergen
Aug 1985 Finse, Norway


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