About Polystichum aculeatum (L.) Roth
This species has the scientific name Polystichum aculeatum (L.) Roth. Mature plants typically produce 3 to 8 glossy dark green fronds, each measuring 30–90 cm long and usually drooping downslope. The fronds are stiff with a hard texture, and are bipinnate (small, young plants only have single-pinnate fronds). Pinnae are arranged opposite one another on the frond stalk. Each pinna is 3–11 cm long, with a large upward-pointing pinnule at its base; other pinnules decrease in size toward the tip of the pinna, and all pinnules have bristly tips. Individual fronds live for 1.5 to 2.5 years, and remain attached to the rhizome even after they wither. Round sori form two rows on either side of the midrib of each pinnule. Each sorus is covered by a centrally attached, umbrella-like indusium with fringed edges, and produces light yellow spores. This fern is distributed across most of the British Isles and Europe, excluding northern European countries; in Ireland, it occurs in the counties of Down, Antrim, and Londonderry. It grows on mountain limestone screes in the Jura and the Alps, and on alpine and subalpine limestone cliffs. Polystichum aculeatum is cultivated as an ornamental garden plant, and has been awarded the Royal Horticultural Society's Award of Garden Merit.
