Polystichum aculeatum

Polystichum aculeatum, the hard shield-fern, is an evergreen fern native to Europe. It is most abundant in the upland regions of the British Isles and western France, where mild winters and moist summers suit it, and it also occurs more locally across most of Europe except northern Scandinavia and northern Russia. In the Mediterranean region it is confined to high altitudes. It grows on steep slopes in woodland and on mountain limestone screes and alpine and subalpine limestone cliffs, and it is sometimes treated as an indicator of ancient woodland. The glossy dark green fronds are 30 to 90 cm long, usually drooping downslope, with typically three to eight fronds on a mature plant. They are stiff, hard-textured and bipinnate, with a large upward-pointing pinnule at the base of each pinna and bristly pinnule tips; the Latin epithet aculeatum means bristly. Round sori sit in two rows on either side of the midrib of each pinnule, covered by an umbrella-like indusium, and release light yellow spores. Individual fronds live for about 1.5 to 2.5 years. The fern is grown as a garden ornamental and has won the Royal Horticultural Society Award of Garden Merit.