In researching and writing about ferns in my nature notes I noticed a tendency for ferns to be named after armour! There is male-fern which seems to have derived its name from chain mail and the buckler ferns where a buckler is a shield buckled to the forearm. So now I have soft shield fern (Polystichum setiferum) for which I can find no notes about the origin of the name but the fern is undoubtedly shield shaped so I presume that is why it is a shield fern. The soft shield fern has soft fronds, there is a hard shield fern which are stiffer and more brittle.
The soft shield fern is a native of damp woods in the west of Britain, in Ireland and Iberia but it also occurs as far away as Turkey and the Crimea. It is an attractive fern that is often found in gardens and there are some cultivated varieties available from garden centres. This may account for why the only site I have found for it in Dorset so far is at Durlston in the woods near the castle which, some years ago now, were part of the castle gardens. Other 'introduced' plants occur here and I am guessing that soft shield fern was introduced in this way.
At first glance it looks like the common male-fern but closer inspection reveals various differences, but the most significant is the ornamental, attractive 'leaflets' on the fronds which, on the male-fern, are quite plain and uninteresting!