Cyrtomium

Holly ferns

Cyrtomiums are commonly called holly ferns due to the resemblance, given a little imagination, of the pinnae to holly leaves. Their numbers, of about 20 species, are extremely limited by fern standards. Distribution is equally restricted with all but one species native to Asia (although Cyrtomium falcatum and C. fortunei have naturalized in various areas of the United States and compatible habitats throughout the world). By contrast, options for ornamental applications and decorative uses from the garden to the shaded shelf by the kitchen window are far from confined. The distinctive, atypical fern foliage serves graciously as a contrast for delicate companions in the shaded woodland community. And, with their leathery constitution, a number adapt to less-than-fern-friendly indoor habitats.

The fronds are evergreen or (in stressfully cold climates) subevergreen. Many are finished in soft matte patinas of light yellow or gray-greens. The exception, of course, is the common Cyrtomium falcatum, which has polished dark sprigs of pseudo-holly foliage, and is welcomed indoors or out. Cyrtomium blades are once-pinnate with an abundance of sori scattered seemingly at random on the undersides. The sori are shielded with peltate (centrally attached umbrella-like) indu-sia. The stipes are proportionately short and usually carry a copious coating of scales. The broad pinnae have prominent midveins as well as netted (interlocking) veins, an impressive picture with backlighting. Three or four vascular bundles have no set pattern.

Cyrtomium comes from the Greek kyrtoma, arched or bulged, in reference to the archlike appearance of the netted veins that are one of the signature characteristics of the genus.

Based on overlapping features, cyrtomiums were in the late 1800s and early 1900s lumped together with polystichums and arachniodes in the now obsolete genus Aspidium. Though now botanically separated, common features remain the same. Cyrtomium and Polystichum both have a peltate indusium protecting the sori on their fertile fronds. However, cyrtomi-ums are distinguished by having netted veins and a terminal pinna, which, while slightly smaller, is similar to the lateral pinnae. In some instances polystichums and cyrtomiums also share a characteristic auricle (thumb) at the base of each pinnae or pinnule. (Think "thumbs-up.") With the large pinnae on cyrtomiums, this feature is either especially obvious or clearly missing, while the "thumb" is a typical feature on polystichums.

Cyrtomiums are easily cultivated and are one of the best options for, but not confined to, deep shade where they will not only thrive but give foliar excitement to somber sites. They are primarily plants for Zones 6 (with considerable protection) to 10. While evergreen, they can, like people, look a little weary in winter. Plant them in the universally recommended fern mix of rich, but light composty duff with good drainage. Some species are from limestone habitats, but limey supplements are not necessary for plant vigor or health.

Spore propagation is very efficient as many species are apogamous (producing plants directly from prothalli) and are extremely fruitful, yielding crops quickly (sometimes even when not expected). Division is generally not an option as the species rarely produce the requisite multiple crowns.

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