Coffee Fern (Pellaea andromedifolia)

The true ferns, which belong to the Division Pterophyta (Class Filicopsida), first evolved during the so-called Coal Age or Carboniferous Period, which extended from 345 to 280 million years ago. The first appearance of ferns predates even the horsetail family (Equisetaceae), another “ancestral” spore-bearing group that dates back to the lower Permian Period (280 to 225 million years ago). These vascular, spore-bearing plants persist on all continents except Antarctica, ranging from tropical to temperate to arctic environments. They include species that float on water and terrestrial plants from sea level to high altitudes. They can range from tiny aquatic forms less than one-half inch in diameter to giant tree ferns growing over 80 feet high. (For a discussion of California’s ferns and those species indigenous to the San Francisco Peninsula, see San Francisco Ferns in the December1996 issue of Yerba Buena News.)

Growing up in the nursery trade, I always enjoyed seeing ferns appear spontaneously beneath our greenhouse benches, out of the drain holes of other potted plants, and even from the wooden gutters overhead. I’m probably not alone in my association of ferns with damp, dank recesses of steep ravines, rock overhangs, moist woods, and tropical settings. When I first began to explore California’s dry, scrubby hillsides, I have always been amazed by the discovery of ferns growing in such atypical locations as the cracks of rocks on south-facing slopes, nestled among chaparral shrubs, on open grassy hillsides, and on exposed slopes at high elevations. The tenacity of these ferns seems so out of character and utterly remarkable.

I’ve singled out coffee fern for this newsletter for its very tough nature, its attractive form, and for its rarity on the northern San Francisco Peninsula. Also known as coffee cliffbrake, coffee fern is a creeping perennial, producing short underground rhizomes and triangular fronds up to two feet long. The fronds are normally tri-pinnate (three times compound) with round, leathery dark green and in-rolled pinnae (leaflets). Sporangia (spore-producing structures) are partially hidden beneath the in-rolled edges of the pinnae. The generic name, Pellaea, is derived from the Greek pellaios, meaning “dark,” possibly alluding to the stalks of this fern which are generally dark. The specific epithet andromedifolia refers to the presence of leaves like those of Andromeda, the bog rosemary.

Coffee fern is usually found in dry, stony places in cismontane California from northern Baja California to Mendocino and Butte counties, including the Channel Islands. It occurs in chaparral, foothill woodland, valley and foothill grassland, and yellow pine forests below 4,000 feet. I’ve seen it growing on dry, rocky slopes in eastern San Diego County, on sites where ferns are about the last group of plants you might expect to encounter.

Coffee fern is one of six species of native members of the genus in California. In their 1958 A Flora of San Francisco California, Howell, Raven, & Rubtzoff cite only a single location of coffee fern in San Francisco. As reported by Katherine Brandegee, the species occurred at Sunset Heights. Our chapter members have reported it from three locations in the chapter area: Glen Canyon, Sharp Park, and Yerba Buena Island. Interestingly, coffee fern has not been recorded on San Bruno Mountain. Elsewhere on the Peninsula, it can be found at Edgewood Park. In Marin County, it can be seen at Angel Island, Ring Mountain, Mt. Burdell, Mt. Tamalpais, and other sites. In the East Bay, coffee fern occurs at Point Molate, the East Bay Hills, Mt. Diablo, and the Mt. Hamilton Range.

Some of the other drought-tolerant ferns that occur on dry slopes in the Bay Area include birdfoot cliffbrake (Pellaea mucronata), goldback fern (Pentagramma triangularis), coastal lipfern (Cheilanthes intertexta), Cooper’s lipfern (Cheilanthes cooperae), Coville’s lipfern (Cheilanthes covillei), lace fern (Cheilanthes gracillima), and California lace fern (Aspidotis californica). Of these, only coffee fern and goldback fern occur in San Francisco County. Birdfoot cliffbrake is recorded in the 1958 flora as having been reported on “hills near Bay View” in the southeastern part of the city; it is no longer found here.

With their soft, lacy texture and bright green leaf color, ferns present a lush, soothing appearance, whether in a natural or landscaped setting. We understandably associate them with moss-covered rocks, near springs and creeks, and in moist woods. But California’s droughty ferns might cause you to reevaluate your stereotypes. During the long hot summer, these scrappy little plants shrivel up to the point where they’re hardly recognizable as ferns. But come winter, they turn green and vibrant, like any proper fern. So, the next time you find yourself traversing a rocky, hot, south-facing slope, don’t forget to keep an open eye, and an open mind, for ferns.

Posted in Focus on Rarities.

Michael Wood

President, Wood Biological Consulting, Inc.
Wood Biological Consulting, Inc. San Francisco State University