Cyrtomium is a genus of approximately 35 species of ferns belonging to the family Dryopteridaceae (subfamily Dryopteridoideae), within the order Polypodiales. The genus is classified under the Pteridophyte Phylogeny Group system of 2016 (PPG I). Cyrtomium is phylogenetically very close to the large genus Polystichum; molecular research published in 2016 indicates that Cyrtomium forms a clade sister to Polystichum sensu stricto, and some treatments have proposed folding it within an expanded Polystichum.
Species are distributed across Asia (their primary centre of diversity), Africa including Madagascar, and Pacific Ocean islands including Hawaii. The best-known member, Cyrtomium falcatum (Japanese holly fern or holly fern), is native to eastern Asia — Japan, China, Taiwan, India, Vietnam, and the Himalayas — and has become naturalised in parts of Britain, Australia, and New Zealand, where it colonises shady walls, coastal rocks, and woodland margins. Its species epithet falcatum refers to the Latin falx ("sickle"), describing the sickle-shaped pinnae that give the plant its distinctive holly-like appearance.
Members of the genus are evergreen ferns with once-pinnate fronds bearing broad, often glossy, ovate to falcate pinnae with netted (reticulate) venation — a feature that distinguishes Cyrtomium from most other dryopterid ferns, in which veins are typically free. Sori are round, borne on the underside of fertile pinnae, and covered by peltate indusia.
Cyrtomium falcatum is widely cultivated as an ornamental for shaded gardens, containers, and ground cover. It tolerates a wide range of soils and pH, grows in semi-shade or full sun, and prefers reliably moist conditions.
Etymology
The generic name Cyrtomium derives from the Greek kyrtos ("arched" or "curved"), referring to the arching habit of the fronds. The most widely grown species, Cyrtomium falcatum, takes its epithet from the Latin falx ("scythe" or "sickle"), alluding to the sickle-shaped pinnae.
Distribution
Cyrtomium species are native primarily to Asia, with additional native occurrences in Africa (including Madagascar) and Pacific islands (Hawaii). Cyrtomium falcatum, the most widespread species, is native to eastern Asia — Japan, China, Taiwan, India, Vietnam, and the Himalayas — and has naturalised in Australia (New South Wales, Queensland, South Australia), New Zealand (first recorded 1981), and coastal and wall habitats in Britain.
Ecology
Within their native range, Cyrtomium species occupy shaded forest understories, rocky slopes, and coastal cliffs. In areas where they have naturalised (Britain, Australia, New Zealand), plants are found on shady walls, among maritime rocks, and at woodland edges. Cyrtomium falcatum tolerates mildly acid to mildly alkaline soils of varying textures and prefers consistently moist conditions, though it can establish in drier coastal environments.
Cultivation
Cyrtomium falcatum is a popular ornamental fern for shaded gardens, containers, borders, and ground cover. It grows in semi-shade or no shade and tolerates a wide range of soil types and pH. Hardiness varies by clone; most cultivated forms are suited to mild-temperate climates and may be grown as house plants in colder regions.
Propagation
Cyrtomium is propagated by spores or by division. Spores should be sown as soon as ripe on the surface of humus-rich, sterilised compost; keep the substrate moist (a plastic bag over the pot helps maintain humidity). Germination occurs within 1-3 months at 20 C. Pot on small plantlet clumps once large enough to handle and maintain humidity until established. Plants should be at least two years old before outdoor planting. Division can be carried out in spring or summer.
