This piece was first published August 27, 2015 at Beacon Reader.
“They’re goddamn invasive plants.”
Biologist Tim Shields had an odd look as he observed a mid-sized shrub in my yard in Joshua Tree, California on an evening late in March. “They’re not native. They’re from South America. They got here somehow and then they colonized the whole desert, taking over thousands of square miles and making an ecosystem that never existed before.”
And then he laughed. He was pointing at a creosote bush, Larrea tridentata, likely the most common woody plant in the California deserts. You won’t find creosote on any list of desert invasive plants. Most plant species move their ranges, and none of the plants currently considered native to the desert have been living here forever. Their ancestors dispersed their seeds here from somewhere else. Or their ancestors grew here, but were of a different species, and their descendants evolved in response to changing conditions. But generally, a species is considered native to the North American deserts is if was here before the deserts were opened to global trade.
Call the cutoff date 1492; that’s close enough for government work. And the shrub Shields was regarding may have been in the desert almost that long. 300 or 400 years, easy.
It’s all about perspective. Shields was taking the long view, abandoning our usual human-scaled frame of reference for something a little slower. Or would that be faster? Rewind the record of life in the North American deserts back about 15,000 years, play it back again a couple hundred thousand times faster than it happened the first time, and Shields has a point. Though it’s thought there may have been creosotes growing in Central Mexico as early as 8 million years ago, the species probably didn’t show up in the present-day North American Deserts — the Chihuahuan, Sonoran, and Mojave — until maybe 13,000 years ago or so.
Play that tape, and creosotes will seem to explode across the Chihuahuan Desert, perhaps with a few false starts as unstable Ice Age climates bring especially cold winters every 500 years or so. A reproductive fluke happened as the plants moved into the Sonoran Desert, perhaps an error in a single seed’s development: Sonoran Desert plants have two pairs of each chromosome compared to the Chihuahuan plants’ single pair. That doubling of chromosome pairs is known technically as tetraploidy, “tetra” referring to the four copies of each chromosome. Botanists who’ve looked into the creosote genome suspect that the tetraploid creosotes may have been better able to survive in the greater aridity of the Sonoran Desert. Moving from the Sonoran into the Mojave, it happened again: some creosote made a mistake in the chromosome copying and collating process. Creosotes in the Mojave have three pairs of chromosomes: they are hexaploid.
So tetraploid creosotes exploded across the Sonoran Desert, and then hexaploid creosotes rampaged across the Mojave, each covering broad swathes of new territory in a seeming eyeblink — at least on our sped-up, Shieldsian timescale. It’s not hard to imagine creosotes spreading rapidly, given the right conditions. The shrubs produce prodigious amounts of fruit, white fuzz-covered capsules with five seeds that are avidly gathered by ants, birds, and other wildlife. The fruit collects in drifts in washes and alongside the raised soil mounds beneath creosote clumps. They are so numerous that a local species of wasp known as “velvet ants” find it evolutionarily advantageous to camouflage themselves as little puffs of white fuzz the size of a creosote fruit. When the desert is awash in creosote seeds, predators specializing in velvet ants would probably prefer looking for needles in haystacks.
So, lots of seeds waiting for the right conditions to germinate. Those right conditions may not come as often as they did back in the Pleistocene. Creosote seeds germinate readily, but then succumb to desert heat unless the next three to five years are unusually cool and moist. That means that many of the creosotes in a typical desert valley full of creosote likely grew in pulses, decades when conditions were right for survival of germinated seeds.
Four months later, sweating out a July day in a broad valley north of my home, I think about Shields’ assessment of creosote’s invasive potential. Toss a fluffy creosote fruit onto the desert soil, and ensure five years of cool wet summers, and you get a seedling with bright waxy green leaves. In a mere decade that seedling may have raced toward the sky, reaching a full foot in height. In just a century or so, its single trunk will grow a shoot from its base, perhaps two or three. They will grow into mature plants and shade out, crowd out their parent stem. It will die back, leaving a hole in the creosote donut. Those stems will grow their own clonal stems, which will grow their own in turn, ripples expanding outward from the seed thrown into the ocean of desert.
The ripple I’m napping in is 45 feet across, more or less. In the late 1970s biologist Frank Vasek and his colleagues at UC Riverside calculated that it had been growing here in the Johnson Valley area for a very long time.
I once heard a joke about a family visiting Chicago’s Field Museum and marveling at a fossilized hadrosaur. “That’s 80 million and 27 years old,” said a nearby custodian. “That seems unusually precise,” said the mom. “Well, they told me when I started working here that it was 80 million years old, and I’ve been here since 1988,” said the worker.
In that spirit, I think of this creosote ring, which Vasek dubbed King Clone in 1980, as 11,735 years old. Give or take.
I’m here with my hiking buddy Monica, who is a biologist, and my dog Heart, an olfactory forensics researcher. We got here with a set of somewhat vague directions, which I improved upon using technology approximately 1/2340 as old as the creosote clonal ring: I fired up my smartphone’s mapping app and we walked until the blue dot was next to the biggest ring of creosote on the map.
Now that we’re here, Heart wastes no time providing the oldest known creosote with a bit of nitrogen, then she wisely retreats into the thin sliver of shade cast by Monica, who has found a place to sit near the edge of the ring.
I intend more contemplation than socializing, so I move twenty feet away to the approximate center of the clonal ring. I lie on my back. I look at the pale, sunburnt sky. I imagine a slow tide of invasive creosote wreaking dilatory havoc across the landscape in a mere geologic eyeblink.
When you start paying attention to very long-lived plants, 11,700 years becomes less impressive. King Clone probably isn’t even the oldest creosote clonal ring: it’s just the one we know about. So much of the desert remains unexplored, unexamined. In the last decade botanists decided a shrub oak about an hour’s drive from here is likely around 13,000 years old. A four-hour drive in the opposite direction, there’s a clonal forest of cottonwood trees thought to have germinated from a single seed 80,000 years ago.
Ancientness lurks everywhere you look in the desert. Vasek estimated the lateral growth rate of creosote clonal rings at about .7 millimeters per year. It’s not at all hard to find creosote clonal rings five feet across. Five feet divided by .7 millimeters is about 2,177 years and seven weeks. Give or take.
I’m something like 11,645 years younger than King Clone, and yet at the rate years seem to be speeding up as they pass me I expect these days that I will catch up in no time. My age is growing steadily and well, mulched thickly with calendar pages. I have shirts not yet threadbare that are older than some of the people I work with. There are urgent tasks I have been reminding myself to finish for 15 years, unfinished conversations fresh in my mind with loved ones long dead.
This past year took about 20 minutes to elapse. It has brought remarkable changes in that short time. A year ago I was resigned to settling for consistent but somewhat manageable unhappiness. I am now happy. A year ago I dreaded the future mildly: I now look forward to it. From hopeless disappointment to occasionally elated optimism is a remarkable change, even more so given the year’s racing past. I have been a bit breathless. Time and change have come at a staggering clip, and despite those changes’ positivity I have wanted a bit of slow.
Slow is here, in abundance. It is layered over with fast, of course: the frisking dog, the flies’ inexorable wingbeats, the plunge of the sun toward the mountains to the west. My shadow grows in length, and yet it is far more permanent to me than I can ever be to King Clone. I am a passing shade to King Clone, a flicker on the far margins of his sleeping consciousness, and if I had had children their great grandchildren might well have come here in their ninth decades of life to find King Clone essentially unchanged, not remembering the afternoon when I was a fly alighting briefly on his shoulder.