Species of the Month - November 2016

Hartstongue Fern

Asplenium scolopendrium
 

As the year draws to a close, many flowering plants die down or lose their defining features, but most ferns keep in good shape throughout the winter, including the Hartstongue Fern which is fully evergreen.  It is very easily recognised as it is the only fern with completely undivided fronds.
 

The underside of the fronds bear linear sori containing the spores.  When young these are covered with a silvery indusium, which opens when the spores are ready for release.  There are actually two sori side-by-side along each vein, but they are so close together that as soon as the sporangia begin to expand, the pair of sori appear as a single brown line.
 

Hartstongue Fern in a shady gully in early March, with previous year's fronds still green and healthy.

Fresh young fronds of Hartstongue Fern in early May, among limestone rocks with Hard Shield Fern.

Fully-expanded fronds in early August, still with a fresh green colour due to being in a sunny location.  The fern normally prefers shaded situations where it develops a leathery appearance.  It needs neutral to alkaline conditions and is absent from acidic rocks unless they are flushed with base-rich seepage, as often happens in the gorges of hill burns.  It is common on mortared walls but is unlikely to be found on dry stone walls unless they are of limestone.

Please send in your Hartstongue Fern sightings using the form below, or email sightings@lnhg.org.uk with the details if you prefer.  If you are not sure of the identity of your fern, please send a photo to sightings@lnhg.org.uk, or put one on the LNHG Facebook page.