On any average Saturday, squadrons of West Seattleites armed with pruning shears and loppers quietly slip into the community's public parks to defeat invasive killer plants and liberate the native flora.

There are numerous horticultural enemies in the parks: Himalayan blackberry vines, holly, laurel, mountain ash. These so-called invasive species block the sun and shade the ground, keeping soil too wet and cold to sustain native plants.

"English ivy is by far the worst," said Ken Shaw, leader of monthly work parties in Schmitz Park and Preserve as well as Lincoln Park. "Ivy can kill even the biggest trees."

Ivy vines grow from the ground up tree trunks and snake into the high branches seeking sunlight. Thousands of ivy leaves capture more wind and rainwater than the tree otherwise would. If temperatures are freezing, ice can form in the foliage to make trees top-heavy and more likely to fall in strong winds.

Ken Shaw began his volunteer work after a windstorm in 1991 blew down a favorite large tree next to Alki Beach.

"In high winds, that tree made a lot of music," Shaw said.

Forceful winds flattened many of the tallest trees in Schmitz Park and Preserve in 1991. Wind gusts of 79 mph were measured at the Alki Point lighthouse and many Douglas firs, alders and redwoods were toppled, including a 300-year-old cedar.

Shaw and other residents wanted to help clean up Schmitz Park and Preserve, so they asked Seattle Parks and Recreation what they could do. The Parks Department suggested they attack the invasion of English ivy.

Shaw is always encouraged by the way nature responds to the volunteers' efforts.

"Plants can recover," he said. "The genetic bank is there. It's ready to go.

"There's hope the forest can recover and regrow," he continued. "But what we need is labor."

Shaw earned a bachelor's degree in art at the University of Washington but, because of poor nutrition and lack of exercise while in college, he went into a lengthy illness. He started gardening for exercise and one thing led to another, he said.

Shaw has held various jobs over the years but none have been as enjoyable or satisfying as working in the parks. Now he donates about 20 hours a week year-round to reforestation in West Seattle parks.

"I feel like I've found something where I'm capable of making a difference," Shaw said.

Last year, volunteers donated about 130,000 hours removing invasive species, planting, mulching and repairing trails in Seattle public parks, said David Takami, Seattle Parks and Recreation spokesman.

Ivy also covers and smothers West Seattle's native forest plants such as sword fern, lady fern, maidenhair fern and salal, said Jeff Sifferman. He supervises volunteer work parties at Mee Kwa Mooks Park on the third Saturday of every month.

In the past two years, volunteers have freed "a few hundred" trees, he said.

"Ivy is the worst invasive we have," Sifferman said. "It's the primary ground cover in Mee Kwa Mooks."

Ivy growth in West Seattle parks continued unchecked for 50 to 60 years, Sifferman said. He recently cut an ivy vine that had 30 rings and was about 4 inches wide. He's seen vines that are 6 inches in diameter.

Some Saturdays, nine volunteers shows up to work. Sometimes only one person comes.

Students from Madison Middle School as well as Pathfinder School volunteer at the park. Occasionally employees of Starbucks, Microsoft, Home Depot or Costco come in force to uproot invasive plants, Sifferman said.

Volunteers are making progress at Mee Kwa Mooks Park.

"In places, there was just a sea of ivy, a couple acres worth," Sifferman said. Once volunteers removed the ivy, the natural ground cover plants had a chance to regrow.

"There are a lot of dormant seeds and roots (of native plants)," he said.

Ivy gets into the parks as a result of birds, Sifferman said. Birds eat the seeds of ivy plants in private yards all over West Seattle and then defecate in the parks.

Sifferman said battling invasive plants is addictive.

"You come back two or three weeks later and see ivy leaves drying up," he said. "You see the tree and almost hear a sigh of relief. It's relaxing and we're making a contribution to the future."

It offers a chance to meet neighbors and build community, he added.

The Seattle Parks Department used to plant ivy on purpose for ground cover and erosion control. It proved to be ineffective at both tasks and became a pest so the department stopped planting ivy in about 1990, Takami said.

About 18 work parties have been held in recent years at Solstice Park (formerly known as the Lincoln Park Annex), where volunteers removed black locust trees and Himalayan blackberry bushes.

Volunteers put about 400 native plants in the ground around the 7.5-acre park across Fauntleroy Way from Lincoln Park, according to Dan Dahl, volunteer coordinator. He's been volunteering his time at Solstice Park for about six years.

Much of the volunteer effort has concentrated on the steep stairway into the park from 44th Avenue Southwest. Native plantings include ferns, salal and Oregon grape among other local species.

Work parties the first Saturday of every month are held along Longfellow Creek near Brandon Street. Volunteers have cleared most of an acre of ivy, then spread biodegradable cardboard over the cleared area and covered it with mulch, said Jay Mirro, volunteer coordinator at the site.

This winter, volunteers are planting Western red cedar, Sitka spruce and Douglas fir, along with Indian plum and shrubs called ocean spray.

The monthly Saturday events usually draw 10 to 15 people, Mirro said. One time, 70 people showed up.

Like many other park projects in West Seattle, volunteers from the nonprofit organization EarthCorps have pitched in at Longfellow Creek too.

EarthCorps has been bringing work crews to West Seattle parks since at least 1999, said Steve Dubiel, executive director of the King County unit, which as about 85 members. Affiliated with AmeriCorps, EarthCorps is based at Magnuson Park.

Founded in Seattle in 1993, EarthCorps has sent work crews to Longfellow and Fauntleroy creeks as well as Roxhill bog. They've labored in Camp Long, and in Lincoln, Mee Kwa Mooks, Greg Davis and Schmitz parks. They've planted trees in the West Duwamish greenbelt and cleaned up around the Duwamish River.

EarthCorps set itself the lofty mission of "building global community through local environmental restoration," according to the organization's web site. Volunteers ages 18 to 25 sign up for six to 18 months to learn conservation techniques and leadership skills.

About 40 percent of EarthCorps' volunteers are foreigners, Dubiel said. EarthCorps hosts foreign volunteers from six different countries who work alongside American volunteers to restore the natural environment on public lands around Puget Sound and the Cascade Mountains. The hope is that young people from other countries will learn environmental restoration techniques they can try at home. EarthCorps also sends volunteers to environmental restoration projects in other countries.

Anyone interested in volunteering in West Seattle parks is urged to contact Janine VanSanden, volunteer coordinator for the south district of Seattle Parks and Recreation, at Janine.VanSanden@Seattle.gov.

Tim St. Clair can be reached at tstclair@robinsonnews.com or 932-0300.