Cheilanthes

Cheilanthes are dryland ferns and quite the opposite of the traditional, stereotypical and beautiful woodland shade lovers that evoke visions of greenery in the world's forests. We cherish and cultivate those for a myriad of reasons, but many avid gardeners also attempt the xerics, including cheilanthes, for their unique ornamental qualities as well as the challenge of establishing notoriously difficult species. And challenging they are. Cheilanthes like arid, desertlike habitats and have developed adaptive strategies for succeeding in sunshine and drought. Most noticeably the fronds and especially the pinnae and small pinnules produce diagnostic cottony hairs and/or woolly scales and occasionally waxy undercoatings that are ornamental to the viewer and functional for the plants. These adornments serve to moderate the ambient temperature around the fronds, to reflect heat and light, and to catch dew and whatever minimal moisture may be available.

In addition most species crowd together to reduce transpiration and snuggle their colonies against rocks to provide a modicum of shade as well as a cool shelter for the extensive, long-running moisture-seeking roots. In severe or prolonged drought the entire fern can curl without damaging cell structure and will rehydrate with the arrival of a good drink. This

Hairy upper surface of Cheilanthes tomentosa as viewed through the microscope. Photo by Richie Steffen, Miller Botanical Garden.

characteristic has earned some of them the epithet "resurrection ferns."

The name Cheilanthes comes from the Greek cheilos, lip, and anthos, flower, in reference to the curled pinnae margins that enclose the sori. They are consequently also commonly called "lip ferns."

There are 180 to 200 species worldwide with high concentrations in the U.S. Southwest and northern Mexico. Most, with their single vascular bundle, are short, usually around 12 in. (30 cm) more or less, and strongly vertical. The blades are often very finely divided, up to quadripinnate, with green, blue, or grayish evaporation-resistant, minute pinnules. Veins are free but usually obscured by the hairs and scales. Unlike most ferns, many cheilanthes are distinct by having noncirci-nate vernation, where the emerging bud is not at the center of a coil, as opposed to the traditional crosier pattern usually associated with unfurling fronds.

Taxonomists have been actively researching relationships among the cheilanthoids resulting in a number of reclassifications in recent years. This will be ongoing, I am sure, as botany is a living science. As of 2005, Argyrochosma, Aspidotis, Astrolepis, Bommeria, Mildella, Notholaena, Pellaea, Pentagramma, and Pityrogramma are all considered separate genera with a preference for xeric habitats. Not all of these classifications are new but some are rearrangements.

It is not necessary to be a geologist or chemist to cultivate these ferns, although it may help. Some species are very soil

Microscopic view of the frond's underside showing hairs and spores on Cheilanthes tomentosa. Photo by Richie Steffen, Miller Botanical Garden.

specific; however, most will respond to some general guidelines. The soil composition must be loose to encourage free drainage whether for basic or acid-loving species. I have had my best successes with mixtures that include volcanic rock, pumice, and/or granite grit, which is sold as chicken scratch and comes in at least three different grades from fine through coarse. It is extremely important to give any of these inorganic additives a good hosing to flush away the siltlike "fines" that can clog oxygen circulation in the soil with devastating results. (Like vermiculite and perlite, these products produce dust that humans should take precautions against inhaling.) I add composted bark, charcoal, and humus to the basic mix. When growing plants in containers, tall narrow pots provide the best drainage.

Protection from overhead winter wet emulates the natural southwestern environment, which gets summer but not much winter rain. Water sitting on the fronds in the cool of winter does not readily evaporate and will slowly destroy the foliage. When watering is necessary, I direct it to the soil and not the foliage.

Plant surroundings need good air circulation. In addition they need bright light as opposed to the conventionally shaded ferny sites. In climates with high heat, light shade is appropriate. In cool, cloudy climates, full sun, at least in winter, is suitable. Experimentation and adjustments are necessary to determine the ideal location(s), and cultivating the lot in portable containers certainly simplifies the "educational" experience.

Theories vary regarding fertilizer with one being that none should be added and the other being that the xeric native habitats are high in mineral nutrients and fertilizer is welcome. I do not feed mine, mostly because of a lack of prioritized time rather than strong convictions, but some of the best xerics I have seen are in bonsai pots and regularly fed. (While these pots are not usually deep, they have extra large drain holes to facilitate the ferns' required good drainage needs.) Whichever course you chose, be sure that applied amounts are no more than one-half of the manufacturer's recommended strength. Feeding for any ferns, including xerics, is most effective when applied during active new growth.

Propagation can be accomplished by division. Established plants do not like to be disturbed, so I selectively remove a piece or two from the perimeter of the plant with a sharp knife. Spore culture is a rewarding option, however, as many species are apogamous, which efficiently compensates for the desert's lack of available water for fertilization. Spores will drop almost immediately when a ripe frond is removed from the parent plant and are so grateful to be sown on a moist medium that they germinate rapidly. (In nature it can be a long wait for suitably ideal conditions to successfully create new plants from spores. In Southern California, native cheilanthes are actively growing during the winter, ready to release their spores with the arrival of the favorable spring conditions.) I use my regular mix of pasteurized earthworm compost for starting the spores, but when transplanting I give them a lean mix enriched with pumice and/or granite grit to emulate their natural habitats. I do not add lime to mixes used with any young plants.

Cheilanthes have many charming species worthy of the extra care to keep them presentable (or at least alive). They are not for beginners. (It helps to live in the Southwest or Southern California.) I recommend them for the specialist's rock gardens and container plantings. And, I especially recommend a visit to the University of California Botanical Garden at Berkeley that has a magnificent and beautifully presented comprehensive collection of these fascinating species.

Far upward 'neath a shelving cliff Where cool and deep the shadows fall, The trembling fern its graceful fronds Displays along the mossy wall. The wildflowers shun these craggy heights Their haunts are in the vale below; But beauty ever clothes the rocks Where Nature bids the ferns to grow.

—Unknown

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