Cliff brakes

Pellaeas, the cliff brakes, are those dusky blue charmers that enchant and taunt from cliff sides, mortared crevices, and other stressful and fern-forbidding sunny habitats with dry and lean, gritty soil. As such, those that are natives of the U.S. Southwest flourish in the challenging sites that delight passing tourists with periodic spring bursts of desert wildflowers but are not traditionally associated with our friends, the ferns. Their exquisitely adapted blue-toned fronds offer beauty to dryland landscapes extending from rocky gulches and tum-bleweed countryside to the stunning panoramas of the brick "Red Rock" country around Sedona, Arizona (a favorite location with or without ferns). While these sites are associated with fern-desiccating sunshine, a closer examination will often find the fern's exposure tempered by the shade of a rocky companion that collects and funnels the minimal available desert moisture to a relatively cool ferny root run. Adaptive foliage color in the xeric species transitions, as light exposure increases, from frosted green to a sun-repellant blue. Ready-

to-curl pinnae are an additional protective mechanism intended to reduce loss of moisture (and life). While these in-rolled needlelike rods give the appearance of a fern struggling in terminal death throes, timely rains will usually rehydrate the fern for yet another season.

Of all the candidates for domestication in temperate gardens, the pellaeas in my opinion are the most difficult. It can be done, however, but it helps to live in California or the drylands of the U.S. Southwest or to artificially create an arid habitat. Pellaea rotundifolia, P.falcata, and other vivid green species associated with indoor cultivation rather than sunny exposures are the exceptions. (Look for them to be reclassified one of these days.) However, even they still prefer the well-drained sites that typify the natural settings for their xeric cousins.

The name Pellaea comes from the Greek pellos, dusky, in an apt description of the blue-gray foliage color on the xerics. Worldwide there are from 55 to 70 species primarily of rocky dryland sites in the Western Hemisphere.

The rhizomes are short- to long-creeping. Stipes are thin, ranging from blueberry through blackish in color, and brittle, indicative of its botanical relationship with cheilanthes and its comparable classification, but not cultural, relationship with the adiantums. (It is also closely allied botanically with Argy-rochosma and Astrolepis.) The penetrating stalks, with a singular vascular bundle, are frequently toxic to grazing animals. Evergreen, naked blades are from once-pinnate to tripinnate with a terminal leaflet matching the lateral pinnae. Free, or in rare instances netted (P. bridgesii and P. ternifolia), veins are not prominent. Sori, protected by reflexed inrolled false indu-sial marginal tissue, line the pinnule perimeters.

Many of the species are apogamous, an efficient adaptive response to their native habitat's sparse supply of the water required for sexual reproduction. In the comfortable and uniform atmosphere provided by nursery propagation (vis-à-vis the uncertainties of natural sites with dodgy and inconsistent weather), they eagerly burst forth from spores. None like to be transplanted, however, so the native populations need to be left in situ and nursery products should be introduced with care to specialized soil and sites. The xeric species want bright airy exposures, but not quite full sun, and will turn weak and spindly in too much shade. Tuck their long-ranging roots in moist but well-drained crevices in rocky sites and give them a matching gritty top dressing. For most growers these are truly plants to be admired rather than cultivated.

Pellaea atropurpúrea Purple cliff brake

Epithet means "dark purple."

Evergreen, 8 to 18 in. (20 to 45 cm). Zones 4 to 9. Dimorphic. Apogamous.

description: The rhizome is short-creeping. Shiny, rounded stipes with fawn-colored curly hairs are characteristically a midnight purple-black and one-third of the frond length. Lance-shaped blades are basally bipinnate grading to once-pinnate on the upper portions of the five to nine pairs of pinnae. Lower pinnae are stalked. Upper are sessile with a terminal pinna matching the shape of the lateral pinnae. The plants are mildly dimorphic with the sterile fronds shorter and less divided than the more upright fertile fronds. Sori are marginal, protected by inrolled margins of false indusia.

range and habitat: This species grows in limestone-enriched rocky crags across a broad expanse of midwestern and eastern North American habitats and extends its range down through Mexico and Central America. Look for it as well in the mortared crevices of old weathered buildings and the associated functional antiquities of bridges and highway abutments.

culture and comments: This species is not eager to grace average gardens, even of inspired enthusiasts. However, it is

Pellaea atropurpúrea in nature's rock garden in Massachusetts.

the "easiest" of all the xeric pellaeas. As is true for most dryland ferns, good drainage is critical and essential. A limestone substrate is also required and beyond that protection from excess winter wet (ironically snow cover serves here) all contribute to a potentially successful planting. Try growing it in limestone rubble, good light but not hot midday sunshine, and a well-drained vertical rock or simulated rock face. In cultivation in western North America it is usually short-lived. It is easily confused with the equally temperamental Pellaea glabella, a fellow limestone denizen of eastern U.S. habitats. The latter, however, with its essentially smooth stipes, is strictly monomorphic, displaying its diminutive fronds in arches over its preferred rocky habitats.

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