Texas Ferns Cross Atlantic
Selaginella peruviana growing with cactus.
When Gunnar Ovstebo and Andrew Ensoll landed in El Paso on August 1, they traded in 60-degree highs in Scotland for a chance to search the scorching Chihuahuan Desert for plants most people would walk right past. The horticulturists from Scotland's Royal Botanic Garden, Edinburgh, were on a mission to find ferns that included remnants of those dominating the Earth hundreds of millions of years ago, before mammals, birds – and even dinosaurs – existed.
With the guidance of Wildflower Center Plant Conservationist Michael Eason, they hit pay dirt over a three-week span, making 35 collections of these flowerless plants in four counties.
The sites they visited ranged from stark, open scrubland outside Presidio, Texas, the lush "sky island" of Mount Livermore in the Davis Mountains and the northern lip of the Rio Grande River, a melting 106-degrees F during their visit. Ensoll glimpsed a mountain lion off in the distance at Big Bend National Park and they both marveled at the tenacity of a drought-damaged fern found on their first collection excursion behind Sul Ross State University in Alpine.
"It felt very sacred, these places we've seen through Michael's contacts. They're really gems of nature," Ovstebo said. "And seeing desert ferns in the wild will help us while trying to cultivate them back in Scotland."
The Norwegian oversees glass houses at the Edinburgh botanic garden where desert and other plants from arid regions are kept to brave Scotland's cold climate. Among the offerings available to visitors is a glass house with a Southwestern U.S. exhibit where creosote, desert willow and Chihuahuan Desert cacti are already on display. To the Southwestern exhibit, they will begin adding more than 30 different species of ferns found in August.
Roadside collecting of cochise scaly cloak fern and a spike moss by Gunnar Ovstebo, Sul Ross State's Patty Manning, and Michael Eason from the Wildflower Center.
"Most people don't expect to find ferns in the desert," Ovstebo said, noting that "we're trying to challenge the public to think beyond the expected."
A river fern or a Boston fern with delicate, saw-toothed fronds is likely what many people envision when they think fern. But more than half of Texas' ferns and related species (pteridophytes) exist in its arid Western half, where water-conserving needs rule all things.
Clambering inside limestone canyons, along granite outcrops and elsewhere, the horticulturists came across a range of ferns, from the snowflake-shaped leaves of star cloak ferns, whose fronds resemble hands when closed up, to the stubby, flat fronds of wavy scaly cloak fern, to spike moss with its scale-like leaves clustered in spikes.
As alien as some of the plants looked, the biggest surprise came from their habitat, which differed from the shady, cooler crevices some ferns favor. "You have an image of where things should be growing," said Ensoll, a Brit who oversees the propagation of ferns at the Edinburgh garden. "But you couldn't actually touch some of the rocks the ferns were growing on without burning your hand."
Examples of a hybrid cloak fern (astrolepis integerrima) plant and flower of stone (selaginella lepidophylla) growing in rocky West Texas terrain.
Eason was equally impressed with the horticulturists' skill at recognizing ferns. "I've learned so much from them about the identification of ferns and their terminology," he said. "It's just something I never focused on while collecting seeds in Texas." Not that the identifications always came easily. Many of the ferns had to be baptized in water before becoming lifelike enough to recognize, and in some cases, months of work will occur back in Scotland to grow them up and confirm identifications. "On a lot of the ferns, the pinnae (frond segments) had shriveled up and curled around, and they'd have just snapped if you'd touched them," Ensoll said, immediately adding that "as soon as it rains, they'll expand and within 24 hours, they start coming alive."
Spores, unlike seeds, are single-celled, making it easier for ferns to produce thousands of the lightweight reproductive packets on the back of their fronds. With ferns in water-rich areas, the spore germinates and develops into a sexual stage that undergoes a fertilization step involving sperm swimming to an egg to produce a new plant. However desert ferns have evolved a quicker life cycle that bypasses the fertilization step to form another, spore-producing fern.
The horticulturists look forward to showcasing for the public diverse attributes of desert ferns such as their reproductive strategy – after growing up the Texas plants from spores over the next year. "We'll plant them out in the glass houses, which have lots of space for the ferns to run around the cacti and the rocks," Ensoll noted, recalling their sun-baked homeland. "But we definitely need to add more rocks first."
All photos courtesy of Andrew Ensoll, Royal Botanic Garden, Edinburgh.