Drought-Tolerant Ferns

Ferns call to mind lush, moist, shady environments. But some ferns grow in environments where little water is available, like the desert. These ferns are called xeric ferns, and are dominated by four genera. They have developed several adaptations to survive in these dry conditions. Xeric ferns stay small, because decreased surface area reduces water loss. The fronds may have a coating, such as hairs or wax, that reflects sunlight and reduces transpiration. These ferns don't generally depend on sexual reproduction, and the fronds may dry up during dry periods and regrow when water becomes available.

Scaly cloak ferns (Astrolepis spp.) generally grow in U.S. Department of Agriculture plant hardiness zones 8 through 11. The leaves tend to be long and narrow and leaflets have tiny star-shaped scales. They usually to grow on rocky slopes and ridge tops. The wavy scaly cloak fern (Astrolepis sinuata) bears round, lobed leaflets with waxy white scales on new leaves, while the Southwestern cloak fern's (Astrolepis integerrima) scales are more dense and the leaflets have an oblong shape. Windham's scaly cloak fern (Astrolepis windhamii) has tightly clustered leaflets with a dusting of scales, while Cochise cloak ferns (Astrolepis cochisensis) have lightly speckled leaflets on erect stems.

The lip ferns (Cheilanthes spp.) have leaflets with thickened edges that protect the spore-producing structures on the undersides, and these leaflets often look like beads. The leaflets are often fuzzy, which is useful for deflecting intense heat. Some ferns with prominent lips include the slender lip fern (Cheilanthes feei), which grows in USDA zones 5 through 8, and the graceful lip fern (Cheilanthes yavapensis), which grows in USDA zones 9 through 11. Coville's lip fern (Cheilanthes covillei) has leaves so plump they resemble beads and grows in USDA zones 7 through 9. Two ferns that produce leaflets covered with downy hairs include Parry's lip fern (Cheilanthes parryi), which grows in USDA zones 8 though 11, and woolly lip fern (Cheilanthes tomentosa), which grows in USDA zones 6 through 8.

Cliffbrake ferns (Pellaea spp.) produces gray- or blue-green leaflets and, unlike other drought-tolerant ferns, are smooth and have no hairs or scales. The leaves are either fertile or nonfertile and each type has a distinctive appearance. Fertile leaves are smaller and have rolled edges. The creeping cliffbrake (Pellaea intermedia), which grows in USDA zones 9 through 11, bears roundish gray-green leaflets, while the leaflets of the purple-stemmed cliffbrake (Pellaea atropurpurea), which grows in USDA zones 6 through 9, are more triangular and matte green with purplish-black stems. Cliffbrakes with narrower leaflets include spiny cliffbrake (Pellaea truncata), which grows in USDA zones 8 through 11, with blue-green leaflets on erect stems and birdfoot cliffbrake (Pellaea ternifolia), which grows in USDA zones 9 through 11.

The cloak ferns (Notholaena spp.) have star-shaped or triangular fronds. The leaflets may have a light waxy coating on the upper leaf surface while the leaf underside may have a heavier coating. The leaf edges are often curled under. Both Gray's cloak fern (Notholaena grayi), which grows in USDA zones 9 through 11, and scaled cloak fern (Notholaena aschenborniana), which grows in USDA zones 10 through 11, have dark green divided leaves with a mealy coating. The fronds of the star fern (Notholaena standleyi), which grows in USDA zones 9 through 11, reveal a star-shape when viewed from above and the undersides have a yellow coating.