Harts Tongue Fern
Can you dig it up and split it (like hosta) or is it just one plant that's not meant to be split?
Found this on The RHS web site.
Propagate by sowing spores in mid to late summer or by
in spring. Peeled leaf bases can be taken off from where the stem joins with the root. Old leaf bases that are green at the base are incubated in a plastic bag of loam based media. Green swellings can be found and potted to raise new plants
they seed (spore) around once they mature
In the sticks near Peterborough