Korean Rockfern

Description

Polystichum polyblepharum, the Japanese lace fern or tassel fern, is a species of plant in the wood fern family Dryopteridaceae, native to Japan and South Korea. Growing to 1 m (3.3 ft) tall and broad, it forms clumps (“shuttlecocks”) of evergreen fronds. The Latin specific epithet polyblepharum means “many eyelashes”. and refers to bristles on the stipe and rachis (parts of the stem). It is grown in temperate regions as an ornamental subject, enjoying damp, well-drained soil in shade or dappled shade. It has been given the Royal Horticultural Society’s Award of Garden Merit. Polystichum is a genus of ferns in the family Dryopteridaceae, subfamily Dryopteridoideae, according to the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus has about 500 species and has a cosmopolitan distribution. The highest diversity is in eastern Asia, with about 208 species in China alone; the region from Mexico to Brazil has at least 100 additional species; Africa (at least 17 species), North America (at least 18 species), and Europe (at least 5 species) have much lower diversity. Polystichum species are terrestrial or rock-dwelling ferns of warm-temperate and montane-tropical regions (a few species grow in alpine regions). They are often found in disturbed habitats such as road cuts, talus slopes, and stream banks. Many ferns of this genus have stout, slowly creeping rootstocks that form a crown, with a vase-like ring of evergreen fronds 30 to 200 centimetres (10 to 80 in) long. The sori are round, with a circular indusium, except in South American species which lack an indusium. The stipes have prominent scales with often have hair-like cilia, but lack any true hairs. The genus differs from the well-known and allied fern genus Dryopteris in the indusium being circular, not reniform, and in having the leaf segments with auricles—asymmetrical blades where one side of the segment is much longer than the other at the base. Apomixis, the development of an embryo without the occurrence of fertilization, is particularly common among ferns. Apomixis evolved several times independently in three different clades of polystichoid ferns.