By JIM WITKIN,

To the untrained eye, a weed is just a weed, and few of us can tell a thistle from a teasel. But for Paul Heiple and his team of Weed Warriors, knowing the difference is essential to their work routing out invasive plants that threaten the native species at Edgewood Park, a 500-acre natural preserve that overlooks California’s Silicon Valley.

Mr. Heiple, a retired geologist, leads a group of about 50 volunteers who spent 4,000 hours last year hunched over the park’s grassland areas digging up culprits like the yellow star thistle, broom, teasel and Italian thistle. They work on behalf of the California Native Plant Society, a nonprofit conservation organization for which Mr. Heiple heads the San Mateo County chapter’s invasive plant group.

I also volunteer on Edgewood Park’s trail patrol, but that job is easy by comparison. Once or twice a week I walk the trails scouting for any safety or maintenance issues and then file a report online. The Weed Warriors, however, engage in regular combat with some 100 nonnative plant species. The work requires a strong back, thick gloves and skill with the hori hori, a Japanese weeding knife with a serrated edge along one side that, in a pinch, could do serious damage in a street fight.

In contrast with high-tech companies in the area that are always rushing to release new versions of their products, the Weed Warriors work backwards and slowly, restoring the landscape to a version of itself that existed before late-18th-century Spanish settlers brought in invasive plant species in the hay used to feed cattle.

This type of labor-intensive restoration is vital to preserving the San Francisco Bay Area’s extraordinary biodiversity, according to Louise A. Mozingo, a professor in the Department of Landscape Architecture and Environmental Planning at the University of California, Berkeley.

“These native ecological communities are increasingly rare,” she said, “and a whole pyramid of insect, bird, and mammal species depend on this diversity.”

Landscape ecologists also realize the significance of maintaining smaller patches like Edgewood Park because they link larger preservation areas together. “Larger tracts of native ecosystems have survived because of the smaller patches, which allow genetic exchanges of all kinds, so every patch is precious,” Ms. Mozingo said.

While preserving the native ecosystem is important, the work also offers a number of personal rewards, said Dave Hershey, who has been weeding for almost three years, putting in about 12 hours a month with his wife, Dianna. Mr. Hershey said he finds his reward in the physical effort, simply being outdoors and chatting with his fellow workers. He said he felt an obligation “to return something for the time I’ve enjoyed at Edgewood.”

He admits, though, that the work appeals to a certain personality. “Patience and an ability to take the long view are useful,” he said, “and given the magnitude of the task, a certain amount of optimism comes in handy.”

Elly Hess, the original optimist at Edgewood, is now a legendary figure in weeder folklore. Growing up on a farm, she learned the importance of keeping weeds out of the garden that provided much of the family’s food.

She started the Weed Warriors in 1989 after a hike with the local Sierra Club group. “I was horrified by the teasel and broom that were taking over,” she said. “All these weeds were crowding out the flowers. I knew Edgewood was special and had to be saved.”

With her husband and a few friends, she slowly built up the group, assembling a core of about 12 volunteers. “There was not much written on the subject at the time,” she said, “so it was challenging to educate people and find recruits.”

When her knees and hands gave out sometime in her 70s, she said, she retired from the Weed Warriors. Now 85, she continues to keep the tomato garden in front of her house weed-free and occasionally volunteers at Edgewood’s new educational center.

Despite some successes, like eliminating most of the yellow star thistle that once covered the park’s grasslands, Mr. Heiple understands that the Weed Warriors’ work will never be done. With new invasive plants appearing all the time, there will always be another weed to pull.

And with many of these invasive plants producing seeds deep in the soil that can survive for several seasons, progress is measured in decades, not years.
Instead, he shares a concern of Ms. Hess about finding the next generation of volunteers. “My fear is when I’m gone, I won’t be replaced,” he said.

(Source: www.nytimes.com )