The scourge of spurge – Naturalists battling for future of Idledale Lake

A Work of Purest Bushwah

Since 2011, hampered by flagging public interest and too few willing hands, the Idledale Naturalists Audubon Society (TINAS) has been locked in a losing battle against an aggressive enemy. Now, 16 years later, the group is marshalling a last-ditch, do-or-die campaign to reclaim Idledale’s natural places from determined and resilient invaders.

“We’re calling it ‘Weed-Free in ‘23,’ and it’s long overdue,” says Hilltop resident Herb Grassley, who took over as the society’s noxious weed coordinator in 2021. “We’ve already lost Idledale Lake, Marmot Meadow is on the brink, and we’re losing hundreds more acres of open space every year.”

For more than five decades, TINAS has been leading the charge against the tide of noxious weed species flooding the mountain area. A mere 20 years ago, the group could count on up to 100 volunteers a year to participate in its annual Community Weed Day at Idledale Lake. Many hands make light work, and one morning each summer generally sufficed to control such noisome trespassers as diffuse knapweed and musk thistle, thus preserving the lakeshores for beneficial, wildlife-friendly native grasses and flowering shrubs. That all started to change in 2011.

“That’s the year we got a double-whammy,” Grassley says. “First, leafy spurge found its way up here from somewhere and started popping up all over the place, and then Dalmatian toadflax got a toehold on the hillside above the warming hut.”

Fighting the same fire on hundreds of fronts, the Humboldt County Weed and Pest Department could provide only minimal assistance, the forest service lacked the funding necessary to mount the all-out assault required to combat the threat, and the Idledale Parks and Recreation District lacked the infrastructure needed for effective action. That left TINAS standing on the front lines, virtually alone.

“We jumped right on it, but toadflax is a perennial that can grow back quickly from root fragments, and leafy spurge roots go down 15 feet, making them almost impossible to eradicate,” Grassley recalls. “Within two years, we were fighting them from the dam to Greystone Manor. It was disheartening for everybody, and I think people just gave up.”


The weed-choked shores of Idledale Lake


Over the next several years, various efforts to stem the toxic onslaught quickly dissolved amid institutional turf wars, funding controversies and bitter methodological controversies. Public interest in weed control reached its lowest ebb in 2011, the same year tamarisk first reared its ugly head in Idledale Lake’s western shallows.

Remarkably rugged and aggressive, the tamarisk’s habit of leaching salt into its surroundings quickly decimated the thick stands of cattails north of Idledale Lake Lodge. Within 5 years tamarisk had supplanted nearly all of the wetland plant species, leaving the broad expanse of water from the lodge to the warming house the thick, green algae soup it is today, and costing Idledale Water customers up to $50 a year in increased purification costs. Deprived of their accustomed fare, ducks and geese all but abandoned the lake, as anyone who’s visited those weed-choked shores recently will attest.

With increasingly fewer hands to tackle a rapidly growing problem, field bindweed daisy soon established itself around the Lake Lodge parking lot. A relentless opportunist, the invader required just two years to erase the native grasses and, by 2014, covered the lake’s picnic area in dense, unbroken mats. While not unattractive, the fast-growing weed is inedible to birds, hastening the area’s feathery exodus.

“I think newcomers to Idledale would probably be surprised to learn that Idledale Lake used to be popular with birdwatchers,” Grassley says. “These days, you might see a half-dozen kinds of birds there, on a good day.”

Perhaps most troubling, field bindweed offers both palatable food and excellent cover for rodents. Relatively safe beneath the plant’s pretty pink and white flowers, mouse and vole populations boomed. County authorities blame the surge for at least 8 documented cases of hantavirus pulmonary syndrome traced back to Idledale between 2017 and last year, as well as for the 2020 tularemia outbreak that sent four members of one local family to the hospital.

The end of Idledale Lake’s usefulness as a public amenity came two years ago, in 2021, when inoffensive-looking myrtle spurge completed its conquest of the lake’s southern shore. Crowding the trail and once-grassy peninsulas, myrtle spurge’s milky sap causes human skin to blister on contact and can be lethal to those with allergic sensitivities.

“When I was in high school, the track team used to train by running around the lake,” Grassley says. “Back then, the only thing you had to worry about was getting caught in somebody’s fishing line. Anymore, you’d almost have to be crazy to want to walk or fish at Idledale Lake.”

While hikers, joggers and mountain-bikers can still safely stretch their legs on Marmot Meadow’s extensive trail system, even that wild haven is succumbing to noxious invaders. At about the same time that field bindweed was crowning itself King of Idledale Lake, oxeye daisy was ascending the throne along Idledale Parkway. Despite dogged control efforts by Humboldt County Open Space, including yearly burnings, the durable perennial dominates approximately 75 percent of Marmot Meadow and adjacent Elk Glen.

A former ornamental that slipped the leash and is gaining ground throughout the foothill counties, oxeye daisy’s expansive root system and stunning reproductive capacities make it a formidable opponent. While pretty, however, the plant doesn’t appeal to deer and elk, which long ago moved on to greener pastures.

“The other day, my son asked me why they call it Marmot Meadow,” says Grassley, shaking his head, sadly. “I told him there used to be marmots in it all the time, but I don’t think he believed me.”

If the situation is dire, Grassley says it isn’t hopeless. Restoring Idledale Lake to its former splendor won’t be easy, but it can be done.

“If we’d had the support to deal with these threats while they were still small, the problems would have been manageable,” Grassley explains. “Now, we’re facing a huge challenge that can only be overcome by a serious commitment from the entire community.

“It might be years before the lake is back to what it was 20 years ago, but, if we do nothing, then one of the best parts of living in Idledale will really be gone for good.”

Used by permission of Evergreen Newspapers