Search the Archive:

February 08, 2006

Back to the Table of Contents Page

Back to The Almanac Home Page


Publication Date: Wednesday, February 08, 2006

Cover story: Fighting WEEDS Cover story: Fighting WEEDS (February 08, 2006)

'Tis the season to take on the pest weeds that are invading our open lands, squeezing out native plants and animals, and reducing diversity

By Marion Softky

Almanac Staff Writer

What do the following have in common? Pampas grass, acacia, French (or Scotch or Spanish) broom, vinca, yellow or purple star thistle, slender false brome, cape ivy, eucalyptus, Himalayan blackberry?

They are all invasive weeds, non-native plants that are moving into pastures and meadows and forests, where they can crowd out native plants, disrupt the food chain for native animals, and change the ecology.

Locally and across the country, brigades of government officials, professionals, and volunteer enthusiasts are banding together to fight this biological pollution. Some will even be descending on Washington, D.C., during National Invasive Weed Awareness Week, from February 28 to March 3.

"Non-natives spread easily. They take over the hills in no time," says Paul Heiple of Ladera, a leader in the fight to restore native landscapes of the Midpeninsula. "Native plants are low-maintenance. They don't need anything from you. They attract birds, and they tend not to die when water is short."

Mr. Heiple, a retired oil geologist with a passion for native plants, has a finger in every weed fight on the Peninsula. He chairs the Portola Valley Conservation Committee, and leads the year-round fight to beat back invasive weeds at Edgewood Park and Natural Preserve.

"We got 2,700 volunteer hours last year pulling weeds at Edgewood. That's a lot of time," he says. "We've had 20 people out there on a Saturday."

"Paul knows everything," says Pierre Fischer, chairman of the Conservation Committee for Portola Valley Ranch, on a weed-watch outing at Portola Valley's Frog Pond.

While Mr. Fischer and Susan Hine pluck at clumps of invasive Harding grass, which have replaced native oat grasses around the frog pond, Mr. Heiple spots one weed after another under nearby trees.

"This is bristly ox tongue -- it's like Velcro. Its roots get really huge," he says, spotting a prickly flat-leaved plant from the mat of early sprouts. "We're winning that one."

Pretty soon we're all plucking tiny sprouts of one of the most aggressive invaders, French broom. "Now is a good time while the soil is soft," Mr. Heiple says.
Fighting French broom

The people who enjoy the gorgeous yellows of French broom and acacia along winter roadsides, may not realize how much damage they do.

"Broom out-competes natives for nutrients; it takes over and crowds out desirable plants," says Mr. Heiple, yanking at a tall plant with the weed wrench he designed himself. "It makes its own fertilizer and grows fast in poor soil."

Still worse, broom makes lots and lots of seeds, which last for 20 to 30 years -- maybe 70 -- in the ground, Mr. Heiple says. "Each flower produces five or six seeds in a pod. Therefore, you should try and get them before they flower."

French broom -- and Scotch and Spanish broom -- present problems on many of the wild and not-so wild lands of the Peninsula and California. "All brooms are bad," says Mr. Heiple.

Ms. Hine warns: "You can still buy French broom in nurseries. They still encourage people to buy that."

The weed warriors don't fight every non-native; they concentrate on those that spread the fastest and do the most damage. And every weed is different. "You have to know each species' Achilles heel," says Mr. Heiple. "And some don't have any."
Yellow star thistle

As the early flowers start blooming at Edgewood Park -- known for its spring displays of California native wildflowers -- yellow star thistle is in retreat.

Thanks to the years-long efforts of Friends of Edgewood, one of the worst weeds in the area is losing ground. Mr. Heiple estimates that determined weed-pullers have cleared some 80 acres and kept the nasty weed from invading the serpentine soils where the unique California natives thrive.

"It's been highly effective. We've taken out huge areas," Mr. Heiple says. "We've moved it back one-quarter mile."

The program still goes on year after year. Mr. Heiple estimates there may still be 100 acres of yellow star thistle at Edgewood out of a total area of 449 acres. Some years the county mowed the weed. "But the county is out of money; we don't mow any more," he says. "Still, every year we push it back -- by hand."

Yellow star thistle afflicts many open lands besides Edgewood Park. In pastures, its deep roots alter the soil and suck up water, reducing the forage value of other grasses. "And it's toxic to horses," Mr. Heiple says.
Jasper Ridge

Even Stanford's Jasper Ridge Biological Preserve is not immune from invasive weeds, says Director Philippe Cohen.

The Stanford scientists do not automatically go after non-natives -- unless they are really destructive. "We look at them as a research opportunity rather than a mere challenge," says Dr. Cohen. "We take a long-term view."

Out of some 850 plant species found at Jasper Ridge, about 80 to 100 are not native, Dr. Cohen says. "We estimate that one-third to one-half of the non-natives are really invasive."

Even Dr. Cohen finds it hard to be tolerant of some of the invaders. French broom is a headache, he acknowledges, as are tree of heaven and acacia. "Our goal is not to eliminate invasives," he says. "Our goal is to protect natives."
Advice to gardeners

As the season to plant this year's garden rushes ahead, Mr. Heiple has advice for people deciding what to plant.

There's a lot of information available from invasive plant Web sites, including a manual called "Don't Plant a Pest," he says. This explains how pretty plants may become pests, and suggests pretty alternatives that are easier to handle and environmentally better.

"Don't plant a pest," Mr. Heiple warns. "You'll regret it. and everybody else will regret it.

"And be sure the plant you select will stay where you want it."


There is an abundance of resources for information about weeds in San Mateo County; several organizations also welcome volunteers to help eradicate bad weeds and plant natives in their place. Here are some of resources: ** The Midpeninsula Regional Open Space District manages more than 50,000 acres of open space on the Peninsula and operates numerous weed-control programs, including one for slender false brome at Thornewood Open Space Preserve. Call 691-1200 or go to ** The Friends of Edgewood Natural Preserve uses volunteers to eradicate yellow star thistle and other invasive weeds. Call Ken Himes at 591-8560 or go to ** San Mateo County Weed Management Area coordinates government and private groups to combat invasive weeds. It publishes a pamphlet, "Invasive Weeds: A Serious Threat to San Mateo County's Natural Resources." This is available online at the agency Web site, most easily found by Googling the agency name and clicking on San Mateo County. For more information, call the county's agriculture department at 363-4700. ** The Watershed Council sponsors numerous volunteer workdays to clear invasive weeds from the banks of San Francisquito Creek and its tributaries, and replace them with natives grown in the council's native plant nursery. Call Katie Pilat at 962-9876 or go to ** The California Invasive Plant Council has a great deal of information on invasive weeds and their control on its Web site: Its booklet, "Don't Plant a Pest" gives backyard gardeners good tips on invasive plants and alternatives. **The Santa Clara Valley Chapter of the California Native Plant Society hosts a Web site with valuable information at

Broom pull day in Portola Valley

Portola Valley will hold its third annual French Broom Pull on Saturday, March 4.

Residents interested in helping the town control the invasive weed that threatens to line its streets and overwhelm its yards should gather at Town Center at 9 a.m. for team signups, coffee and donuts.

Volunteers should bring work gloves; the town will provide weed wrenches for larger plants.

For information, call Marilyn Walter at 851-8181.

E-mail a friend a link to this story.

Copyright © 2006 Embarcadero Publishing Company. All rights reserved.
Reproduction or online links to anything other than the home page
without permission is strictly prohibited.