Desert Blooms

Natural History, May, 1999 by Barbara Kingsolver, Steven Hopp

THIS LAND

The spring of 1998 was the Halley's comet of desert wildflower years. While nearly everyone else on the planet cursed the soggy consequences of El Nino's downpours, here in southern Arizona we cheered the show: desert hills and valleys colorized in eye-popping schemes of maroon, indigo, tangerine, and some hues Crayola hasn't named yet. Abandoned cotton fields--flat, salinized ground long since left for dead--rose again, wearing brocade. Highway medians crowded with lupines and poppies looked like seed packet promises come true.

The first warm days of March always appear to call out a kind of miracle: the explosion of as many as half our desert's flowering species into a brief cycle of bloom and death. Actually though, the call begins subtly, much earlier, with winter rains and gradually climbing temperatures. The intensity of the floral outcome varies from one spring to the next--that much is obvious to anyone who ventures outdoors at the right time of year and pays attention. But even couch potatoes could not have missed that 1998 was a special year: full-color wildflower photos made the front pages of every major newspaper in the Southwest.

Our friends from other climes couldn't quite make out what the fuss was about. Many people aren't aware that the desert blooms at all, even in a normal year, or of how much effort we devote to prognosticating. "Is this something like Punxsutawney Phil on Groundhog Day?" asked a friend from New York.

"Something like that. Or the fall colors of New England. Here, the experts take measurements and make forecasts all through the winter. This year they predicted gold, but it's way past platinum. In a spot where you'd expect a hundred flowers, there area thousand. More kinds than anybody alive has ever seen at once."

"But these are annual flowers?"

"Right"

"Well, then ..." Out nonbiologist friend struggled to frame her question. "If they weren't here last year, and this year they are, then who planted them?"

"God planted them!"

We glanced at each other nervously. A picturesque response, indeed, from scientifically trained types like ourselves. And yet it seemed more compelling than any pedestrian lecture on life cycles and latency periods. Where did they all come from? Had seeds just been lying around in the dirt for decades? And how is it that when called to attention by a higher power than calendars, all at once there came a crowd?

The answer is as complex as a Beethoven symphony. You could look at a lot of sheet music and still be knocked out by the concert. The magic is in the timing, the combinations--and the extent of the preparations.

For the plants, a flower is just the means to an end. The performance is all about seeds, and the object is persistence, through hell or high water--both of which are features of the Sonoran Desert. In winter, while snow falls on much of North America, we get slow, drizzly rains that can last for days and soak the whole region to its core. The Navajo call this female rain, as opposed to the male rains of late summer: rowdy thunderstorms that briefly disrupt the hot afternoons, drenching a small plot of ground while the next hill over remains parched. It's the female rains that affect flowering, and in some years, the benefaction trails steadily into spring. In others, after a lick and a promise, the weather dries up for good.

Challenging conditions, these, but desert wildflowers have had millennia to come to terms with their inconstant mother. Once a plant rushes through growth and flowering, its seeds wait in the soil--not just until the next time conditions permit germination but often longer. In any one year, a subset of a species' seeds don't germinate; they're programmed for a longer dormancy. This seed bank is the plant's protection against a promising rain followed by drought. If every seed sprouted and died before setting seeds, the species would perish. Some he in wait, loading the soil with many separate futures.

Larry Venable and his colleagues at the University of Arizona have spent years examining the intricacies of seed banks. Desert ephemerals, they've learned, use a surprising variety of strategies for coping with a climate that refuses to reveal--in the span of human observation--predictable cycles. Even in years as wet as 1998, desert natives do more than seize the moment. They also stash away a range of competitive possibilities for the future--a strategy made possible by genetic variation (both among and within species) in their schedules for germination, flowering, and setting seeds. Some species even vary seed size: larger seeds make more resilient sprouts, while smaller ones are less costly to produce. As a consequence of all these adaptations, native desert flowers can hold their own against invaders from greener, more predictable pastures.

The term used to describe these remarkable plants--ephemeral annuals--suggests something captive to the calendar and as fragile as a poppy petal. That is our misapprehension, along with the notion of this floral magic show--now you see it, now you don't--as a thing we can predict and possess, like a garden. In spite of our determination to contain what we see in neat annual packages, a blazing field of blues and golds is neither a beginning nor an end. It's a blink in the long life of a species, whose blueprint for perseverance must outdistance our record books. The flowers will go on mystifying us, answering to a clock that ticks so slowly we can't live long enough to hear it.