SANTA CRUZ >> It was 10 a.m. and spitting rain when the volunteers emerged from the warmth of their cars at Wilder Ranch State Park on a cool Saturday in November. They had a job to do: tear out fistfuls of the fleshy, blade-shaped ice plant overtaking a bluff along the ocean.

And Linda Brodman wasn’t surprised that even on the wettest Saturday in months, nearly a dozen men and women had shown up in the bleak 55-degree mist just to pull up weeds.

“They’re hardcore,” the habitat restoration director said with pride.

The volunteers are nature crusaders from the California Native Plant Society who are passionate about keeping invasive species from choking out indigenous plants. The Santa Cruz chapter, about 200 members strong, endeavors to rid its parks of nasties such as the water-guzzling ice plant, the quick-spreading French broom and the seed-shooting pampas grass.

More than weeds

But these citizen scientists are more than a band of weed-killers. In Santa Cruz County alone, they’ve mapped local flora, classified some as endangered species, and won court battles to protect habitats from development. And because many board members are on the staff of research institutions, the 50-year-old society and its 34 chapters have become conduits between academic research and the real world, like a plant’s xylem and phloem transporting nutrients to its leaves.

Non-native plants are defined as those that arrived, intentionally or not, when Europeans settled in North America. Not all non-native plants are harmful, but those few that tear through ecosystems and crowd out natives are deemed invasive.

These wildly spreading pests can increase erosion, clog waterways and raise the risk of wildfire. The California Invasive Plant Council estimates that efforts to control the intruders cost the state at least $82 million each year, while damage to U.S. farmland totals $33 billion.

But weedy invaders aren’t the only dangers to natives: The society also works to defend everything from tiny flowers to towering trees against the scourges of climate change and human development.

Like the blossoms it protects, the Santa Cruz chapter is small but mighty. A recent achievement was publishing a detailed inventory of all the plants in the area, says chapter president Deanna Giuliano.

“It helps all land managers and developers, knowing what we have here in the county,” she said.

Brett Hall, a past state president of the society, says the checklist sets this county apart from others.

“It’s used by students, by researchers, by agencies; it’s the source for local flora,” said Hall, director of collections and conservation at the UC Santa Cruz Arboretum.

And the chapter intends to keep those local flora around. Hall pointed out that chapter members have been instrumental in putting local species on the federal Endangered Species List. The Santa Cruz Cypress, for example, grows in only a handful of groves in the Santa Cruz Mountains. After nearly 30 years classified as endangered, the tree was downgraded in 2013 to “threatened” — a sign the protection is working.

A protected area

In 2007, the society also negotiated with the developers of a Branciforte Creek housing project to create a legally protected area for the robust spineflower, an endangered herb related to buckwheat.

The common thread weaving these efforts together is the brute force of volunteers. But this reliance makes bringing in new members a crucial task. Brodman pointed out that her restoration team of 40- to 60-somethings may be loyal, but “we’re not the youngest folks.”

To attract younger members, Giuliano, 47, hosts a teen group before board meetings on the second Monday of every other month. The teens bring in plants from their backyards, and Giuliano demonstrates how to identify them.

But for many of today’s high school and college students, that may not be enough. Savannah Robinson, a junior at UC Santa Cruz, was the only weed-killer at the Wilder Ranch bluff below the age of 50 aside from two state park employees.

“My peers are really into incentives,” things like class credit and resume bullet points, Robinson said a little apologetically.

But for those pulling up weeds, the incentives stare right back at them. Many native plants lay dormant in the soil as seeds, just waiting for dominant species to be restrained before sprouting again. Unlike poor Sisyphus, doomed to roll a boulder uphill for eternity, volunteers rapidly see the impacts of their work.

“It’s really gratifying to come back year after year and see what a difference it makes,” said Ann Lundin, a Mountain View nanny.

Even after a few hours in the bone-chilling rain, Brodman had to order her volunteers to drop the ice plant and pack up for the day. Then came the chocolate cookies and carrot cake muffins she had stashed in her backpack.

While they munched, the volunteers traded restoration experiences like war stories — that time the group uncovered a San Francisco garter snake in Pescadero, the rare rain orchid that Brodman stumbled upon in Quail Hollow.

But as Brodman packed up the cookie wrappers and looked back over the bluff, she noted that ice plant re-roots easily and needs to be checked every few months.

“We’ll be back,” she said.