NATURE NOTES:
Ocotillos: New Research Reveals the Importance, and Vulnerability, of an Iconic Desert Plant

By Andrew Stuart

They can live for 400 years, their spiny, twisting stems stretching 20 feet into the sky. Their red flowers bring luscious color to the desert, in even the driest of springs. Ocotillos are found from West Texas to California and the Baja Peninsula – icons not only of the Chihuahuan Desert, but of arid North America itself.

Desert ecologist James Cornett launched a study of ocotillos in 2008 – at sites across the Southwest. His research is ongoing, but it’s already shed new light on this striking plant. Ocotillos play a vital role in desert ecosystems – for one charismatic group of creatures in particular, he’s found. And as hardy and adaptable as they are, ocotillos are being pushed to the brink by climate change.

“I often talk about its iconic status,” Cornett said, “because if you drive through anywhere in the Southwest, frequently people use ocotillos in their business logos. They may even use the name. And I defy you to find a city of, let’s say, over 10,000 people in the American Southwest that doesn’t have an Ocotillo Street, Road or Boulevard. So it’s a pretty well-known plant.” 

Former curator of the Palm Springs Desert Museum, Cornett has written more than 20 books on desert subjects – including on marquee plants like the saguaro and Joshua tree. But the ocotillo beckoned – as a touchstone plant across the desert Southwest.

He selected 10 study sites on public lands – from Big Bend and Carlsbad Caverns to Joshua Tree National Park. His first surprise was how different ocotillo populations are across that range.

The plants are far more abundant in the east. At his study site in Big Bend, north of Panther Junction, Cornett found more than a hundred ocotillos per hectare of land – compared to 20 or 30 plants per hectare in the California desert. Yet while ocotillos are more abundant here, they are smaller, and younger, than their western kin.

The Chihuahuan Desert receives most of its rain in summer monsoons – in the Sonoran Desert, by contrast, rain comes in winter. Summer rains appear to facilitate germination and new ocotillo growth here.

Indeed, in his decade-plus research, Cornett has found no new plants at his California study sites. There’s no mistaking the impact of climate change. In the Sonoran Desert, prolonged droughts – of three years or more – are now twice as likely as they were half a century ago. And that trend could extend to the Chihuahuan Desert.

Ocotillos define desert hardiness. But they do require some rain – typically 5 to 8 inches a year.

“So now we’re really pushing the very limits of some of our iconic desert plants,” Cornett said, “pushing the limits of their survivability under this changing climate regime. One year is not a problem for ocotillos, but when we’re talking about more than three years, you’re really reaching the limits. You get to the tipping aspect of the entire ecosystem.”

Climate change is having other effects – and creating opportunities for ocotillos. The plants are expanding their range northward – Cornett found ocotillos in the southern Mojave Desert. And they’re moving upward. 

Historic accounts indicate ocotillos rarely occurred above 6,000 feet in elevation. Now, in the desert-mountains of New Mexico and West Texas, they’re taking hold above 7,000 feet. 

But intensifying drought could threaten ocotillos’ survival across the Southwest. And like every being, ocotillos are part of a complex web of relationships.

A central finding in Cornett’s research is the close bond between ocotillos and hummingbirds. Hummingbirds are the plant’s primary pollinator. And ocotillo flowers are a crucial source of nectar for the 10 species of hummingbirds that migrate through the Southwest from Mexico each spring. 

A recent study in Arizona found that, with warming temperatures, ocotillos there are blooming two weeks earlier than they did a decade ago. If that pattern expands and continues, it will spell serious trouble for migrating hummers. 

“So if you’re a late migrant hummingbird and you’re coming through the Southwest in April,” Cornett said, “there may be a situation where the ocotillos have already bloomed and have gone to seed, and these late migrants are going to find that the last source of nectar is gone. For a hummingbird with rapid metabolic rate, they are going to expire quickly. The prospect that a changing climate might somehow negatively impact hummingbird populations should be of concern to all of us.”

Feeders can be a boon for hummingbirds, but nature’s complex chemistry isn’t easily replicated – and attentive birders know that hummers will generally choose an ocotillo bloom over a feeder. Cornett urges desert dwellers to plant ocotillos. Stems shouldn’t be harvested from the wild – but if you have a neighbor with a flourishing ocotillo, four or five long stems, planted together a foot deep, can yield a flowering ocotillo plant within two years. The hummingbirds, Cornett said, will thank you.

In their strange, arresting form, and in the unlikely vividness of their blooms, ocotillos embody the haunting beauty of the Southwest. We can no longer take their presence for granted.