An Inconvenient Plant

These days, a boy as obsessed with plants as Peter Raven was would probably have his phone tapped by the Drug Enforcement Administration. In 1951, however, the nation's priorities were different — the Red Menace overwhelmed the green one — and so the 14-year-old spent hours traipsing about the Presidio collecting samples.

But with all of his accolades (and, it seems, deification), Raven knows you never forget your first species.

"It was a cool, sunny day like you often get in winter," he recalls. "I would head into the Presidio on weekends, looking for plants. I would come in at Baker Beach and collect on the bluffs. And I went up the hillside — and there was this plant. I knew it was a manzanita, but I didn't expect to see a manzanita there of any kind. People know the distribution of things pretty well, and manzanitas just weren't known there."

Yet it turned out the plant Raven had just stumbled across wouldn't be known anywhere else. The generations of ecologists and gardeners who have tended the manzanita "mother plant" — which is estimated to be more than 100 years old — since Raven's discovery have been won over by its sheer tenacity. While its forebears couldn't survive San Francisco's housing boom in the 20th century, the final bush is a plant that knows how to cheat death.

In 1958, oblivious Army landscapers undertaking a construction project halted their bulldozers only 20 yards from the manzanita. Thirty years later, a crew of Army lumberjacks felling large pines shading the mother plant nearly landed a tree on it. In rainy years, the plant develops a fungal infection called black smut that often kills 40 percent of its leaves and branches. And, in 1999 and 2000, it was swarmed by hordes of ravenous insects.

"It was like, 'Aaaaaah! The Raven's manzanita is being attacked!'" recalls Kirra Swenerton, the seed ecologist at the Presidio's native plant nursery.

When a horde of tussock moth caterpillars descended upon the plant not long ago, frenzied Presidio employees were relegated to picking off every last one by hand. "There's just the one [manzanita] left, and it's so vulnerable," Swenerton says. "And for that species to go extinct under our watch, in a national park — I mean, where else would you expect people to take better care of it? Oh, I was freaked out."

While the mother plant has escaped death, it has hardly lived a fruitful life. No Raven's manzanita seedlings have ever been discovered in the park.

Shortly after the Army nearly bulldozed the plant in 1958, numerous cuttings were taken. These were planted and cultivated into living insurance policies; roughly a dozen "clones" exist within about 100 yards of the mother plant, in addition to specimens at Tilden Park and UC Berkeley. As the name indicates, clones are genetically identical to the original — the sole genetic individual is the mother plant, leaving the species vulnerable to disease and changing conditions. Scientists can replicate Raven's manzanitas like so many photocopies, but without genetic variability a species cannot evolve. In the long run this, too, is a death sentence.

Botanists have long pegged the Raven's manzanita an "obligate outcrosser," requiring another genetic individual to pollinate it. With none in existence, decades of scientific reports gauged the species' hope of recovery as low.

Still, its champions cop the same attitude as Han Solo careening into an asteroid field: "Never tell me the odds." Allowing the manzanita to die without a fight would be "like burning down the library without reading the books," says Holly Forbes, the curator of the University of California's Botanical Garden in Berkeley. "You don't know what you've missed."

Restorationists like Forbes and Swenerton see the manzanita as "one of the last San Franciscans," a link to the days when Lieutenant Colonel Juan Bautista de Anza first ambled into the city limits — and got sand in his boots.

Dune restoration in the Presidio is not an abstract concept, but a concrete one. Or, more accurately, it's sand — 70,000 tons of it. This mountain of sand, which was trucked over from the de Young Museum construction site, is roughly the size of a high school gym.