GOLD HILL — What passes for a garden herb in Britain has become the latest invader trying to commit unjustifiable herbicide among Southern Oregon's native plants.

GOLD HILL — What passes for a garden herb in Britain has become the latest invader trying to commit unjustifiable herbicide among Southern Oregon's native plants.

The garlic mustard that has taken hold in a corner of Valley of the Rogue State Park is palatable enough to garnish a human salad. But if left to its own devices, it can produce enough seeds to take over huge swaths of the park and beyond.

"There are some recipes for it," says Amy Wilson, who heads the noxious weed-busting Southwest Oregon Resources Conservation Council. "Unfortunately, its recipe is 'take over.' "

That's why Wilson and as many as 100 other "weed warriors" will take to the park and five other sites Saturday to stick up for native plants by pulling and removing non-native weeds.

The second annual "Let's Pull Together" event is expected to draw about 100 volunteers to help yank and bag garlic herb and a host of other non-native plants, such as starthistle, Scotch broom, puncture vine and purple loosestrife.

They all are plants targeted by the 3-year-old Jackson County Cooperative Weed Management Area, a consortium of public agencies and private groups focusing on curbing the geometric growth of non-native plants here.

Noxious plants can be the bane of native ecosystems, overtaking habitats and squeezing out native species. Their presence can reduce wildlife and livestock forage, damage recreation sites and even increase fire danger.

A 2007 federal Bureau of Land Management study concluded that noxious weeds on all its lands were expanding 8 percent to 12 percent per year.

"That's why we have to get at these things as soon as we can," says Vince Oredson, manager of the Denman Wildlife Area, where volunteers will be pulling Scotch broom by the bushel.

Other sites include Prescott Park on Roxy Ann Peak, the Denman Wildlife Area in White City, Lower Table Rocks near Central Point, and Ashland's North Mountain Park and Jefferson Nature Center.

Most will be targeting starthistle, a nasty and bristly plant that, while common in Jackson County, already has overrun large swaths of Josephine County, where it displaces forage plants for livestock and wildlife.

"In Josephine County, it's out the barn door and we're giving chase, but it hasn't taken over here," Wilson says.

At Valley of the Rogue, the top target is Alliaria petiolata, aka garlic mustard.

Discovered last year, the patch now at the 173-acre park is the only confirmed site outside of the extreme northern end of the Willamette Valley, says Andre Briggs, the park's manager. Patches of the kidney-shaped and scalloped leaves are so pervasive they can over-run woodland flowers. The seeds can lie dormant for five years before sprouting.

The plants are along a Rogue River trail near the park's campground, and the seeds can be spread by small freshets or even by hitching a ride in the pant cuffs and shoe-laces of hikers, Briggs says.

Plans are to pull and bag the younger plants now before they can start casting their seed and spreading, Briggs says. Crews will come back in the fall and chemically spray the area as well.

Though brought to North America as an herb or medicinal treatment, the plant is so unyielding it even grows beneath otherwise impenetrable Himalayan blackberries, perhaps Jackson County's top invading plant — for now.

"It's like 'The Battle of the Invasive Species' and who's going to win out," Briggs says.

Reach reporter Mark Freeman at 776-4470, or e-mail mfreeman@mailtribune.com.