Rick Halsey is in search of senile shrubs.

He rolls up California state Highway 79 in his Chevy pickup across the high tablelands of eastern San Diego County. Past a little adobe chapel from the Mexican era, he turns onto an unpaved road. He bumps along in low gear as the road rises into the granite mountains.

In a shallow basin called Indian Flats, he comes to an abrupt stop.

“Let’s say hello to this guy,” said Halsey.

The rangy naturalist strides across a ditch like he’s meeting a long-lost friend. He climbs the side of a boulder, crouches in the shade of a 15-foot manzanita and gazes at the burnished red skin of its bark against the mountain sky.

“This guy might be 125 years old,” he said, giving it a pat.

He knows many forest managers would call this old hardwood “senescent” or “decadent” — terms for native vegetation that has supposedly gone un-burned for too long and is thus an unnatural fire hazard.

Halsey, 53, likes to point out the absurdity of this theory, as he sees it, by simply calling the plants “senile,” as if the manzanita were in an advanced state of dementia.

Chaparral, he said, does not need to burn to the ground every 30 years to remain healthy. Just the opposite. Too much fire will eventually decimate the native flora — some of the most diverse in the nation — leaving a biological wasteland of invasive weeds.

Many people might not know the difference, viewing chaparral as a brown, dead thicket of thorns and brush.

But with the help of top botanists and fire ecologists, Halsey is on a campaign to correct the record about California’s most widespread, misunderstood and maligned type of vegetation.

In doing so, he hopes to limit brush clearance plans to the edges of suburbia, away from the backcountry.

Like the shrubbery he promotes, he is a bit quirky, with a child’s mix of untethered imagination and energy that is labeled eccentricity in an adult, and that his wife lovingly tolerates. He built his family home in Escondido, Calif., to resemble a medieval castle, with a watchtower and a working drawbridge and a long, dark den filled with swords and suits of armor.

But he and his ecological research are respected by leading minds in the field.

The former high school biology teacher founded the California Chaparral Institute, a nonprofit environmental group, and gives talks all over the state.

Through science, Halsey wants to show chaparral’s subtle beauty and the limits of its remarkable adaptations to survive.

It is a lesson in the ecology of drought and fire.

Born of fire

The story of the senile Eastwood’s manzanita, its muscular root anchored to fissures in the granite boulder, is as good a way as any to start it. The stocky stalwart with a bright green head of leaves was actually born of fire.

As a seed, it fell from its parent and, by good fortune, landed in a crevice in the rock where water and dead leaf matter naturally amassed. It may not have sprouted for years — the seed may have just sat there, dormant, for more than a century.

Then came a fire. Smoke from its incinerated forebears woke the seed.

Scientists don’t understand the precise chemical mechanism of this process, but it is the only way to germinate the five species of manzanita in Southern California, as well as many other endemic plants. As fire destroys one generation, it primes a new crop.

When the next rains came, the seed sprouted, its rock confines helping it. Manzanitas have strong roots that pry open fissures and hair-like capillaries that extract microscopic drops of moisture from between the crystals in the granite. In fact, the rock actually retains water much better than soil does.

A slow process

While evaporation off the leaves pulls water and nutrients up through the roots like juice through a straw, the manzanita must drink slowly in this dry terrain. Its silver-green leaves point to the sky so the midday sun doesn’t beat down straight on them. Fine hairs create a buffer around the leaf to limit wind from speeding up the evaporation process. And the microscopic pores in the leaves where the water exits — the stomata — are narrow, sunken and tangled with hair.

“The stomata on a manzanita look like an old man’s ear,” said Halsey. “Full of hair and wax.”

This slows photosynthesis and growth.

So a century-old plant like this one is only 15 feet tall — and Southern California is a land of shrubs.

Hiking through the chaparral and coastal sage scrub of Southern California, Halsey never gave much thought to the shrubs. It wasn’t until the mid-1980s, when he was teaching biology at Serra High School in San Diego on a windy day and a crusty old sycamore leaf drifted through the door like a drunken epiphany.

“Let’s go down in the canyon,” he told his students.

Halsey didn’t know much about the plant life, but he knew his insects and birds. As a child, he spent hours at a time hunting the canyons around Goleta, Calif., for butterflies and bees.

Soon, he had his students help him cut a trail, and he held two lessons a week in the canyon next to school. He taught the children bird calls and quizzed them the next day. But he was at a loss for words when it came to the vegetation. He asked another teacher, an amateur botanist, to teach him about the plants in the canyon.

“It was an explosion of knowledge for me,” he said.

His relationship to the land sharpened and deepened.

“There’s two ways to go to a party,” he said. “You can go to a party and stand there and not really know anybody’s names. Or you know them and their names. It’s a whole different experience.”

The sound of nature

A San Diego Tribune reporter who visited his class in 1990 found them singing, a la Julie Andrews: “The chaparral is alive with the sound of the rufous-sided towhee — cluck, cluck, cluck, cluck, cluck.”

That year, Halsey was named teacher of the year for the San Diego school district.

He received a grant and started writing a book about the chaparral, meeting with scientists, environmentalists and firefighters.

Soon, having the good fortune of a business consultant wife who could pay the bills, he quit teaching to become a full-time researcher, writer and advocate.

Devastating firestorms in 2003, 2007 and the last two months have worsened chaparral’s public relations problems, however.

But it is an insult to nature’s ingenuity, Halsey said, to label the vast biodiversity of the California’s most extensive plant community “brush” and to discuss it only in terms of “fuel load.”

“People have a really twisted view of this beautiful ecosystem,” Halsey said.