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Wildfire opens door to weed control program.

Artichoke thistle, an exotic weed, is being evicted from 17,000 acres of southern California coastal country. The Laguna Beach wildfire created an opening for state and local officials to effectively control the weed and make possible a resurgence of native plant species.

What makes this habitat restoration project different from many others nationwide is that officials are not trying to quickly reclaim the land with aggressive seeding and planting of native species. They believe that if they control artichoke thistle with a herbicide program, native plants will surface naturally and thrive.

"We don't have to spend tons of money on seeding and irrigation and things like that. The native plants will come back if we just skew the environment in their favor by controlling the thistle," said Bill Tidwell, supervisor of field operations for the Orange County Environmental Management Agency.

The suddenness of the wildfire and ensuing herbicide program brings an abrupt end to the slow but steady intrusion of the artichoke thistle. David Pryor, a resource ecologist for California State Parks, said the weed moved in only after cattle, allowed to graze in local grassland, disturbed the soil and gave the thistle a foothold. The cattle were brought in more than 100 years ago; artichoke thistle was introduced either at the turn of the century as an ornamental or appeared as an offshoot of the globe artichoke, which is still cultivated as a food crop, according to Pryor.

Artichoke thistle is a perennial, and mature specimens have a tap root about 8 ft deep. The plant grows about waist high, and flower stalks reach six ft or more. It has long leaves adorned with piercing needles and purple flowers that produce thousands of seeds each year. The seeds are relatively heavy and are not carried far by the wind, so the plant tends to spread slowly and establish thick stands. "And artichoke thistle is allelopathic, meaning it exudes chemicals that keep other plants from growing under its canopy, so it tends to become a mono-culture," Pryor stated.

He added, "In some areas, artichoke thistle has such a grip that it turned grasslands into zero habitat value for the native flora and fauna. None of the native animals have adapted to eating the seeds or living around the plant."

Purple Tide Turns

On October 27, 1993, the artichoke thistle story reached a climactic turning point: an enormous wildfire. The blaze started about noon and was driven by winds gusting up to 60 mph. By the next morning, the Laguna Beach fire had destroyed 386 homes and charred 17,000 acres in a miles-long canyon between peaks as high as 1,500 feet. The fire seared away all visible vegetation.

What emerged from the blackened earth was opportunity. "The fire got everyone to look at this land, and there was nothing but thistle to see because it was the first thing to come up through the ashes. People spotted 50- and 100-acre stands of the stuff within 10 days, and it really captured their attention. The thistle had been there for years, but other plants covered it up. It was never so blatantly clear as after the fire. Within ten days we had plants a foot high or more," said Tidwell.

The newly-obvious threat of artichoke thistle in the burn area "shocked people into action," Tidwell commented, and a coalition was formed to address the problem. The group included representatives from government (the city of Laguna, Orange County, the California State Parks, and the federal Fish and Wildlife Service), environmental groups (the Nature Conservancy and the Laguna Beach Coastal Greenbelt Authority) and a private land owner (the Irvine Company). Most of the money, $100,000, for the $115,000-spraying project came from the National Communities Conservation Program. Coalition members provided the remainder.

The Time Was Right

The wildfire made artichoke thistle vulnerable to the coalition. Without the protective cover usually provided by other vegetation, the thistle plants could be sprayed with relative ease on public and private land scorched by the blaze. "But if we didn't do something right away, the artichoke thistle would gain strength and area because it's more aggressive right after a fire," Tidwell noted.

A 12-man crew, including Tidwell, used backpacks and tanks attached to 300- and 400-ft hoses to hand-spray Roundup' herbicide on the thistle. A pre-emergent herbicide, Telar[TM] (DuPont Agricultural Products, Wilmington, Delaware), also was applied to inhibit regrowth of the pest from buried seeds. Large stands of thistle were sprayed aerially with Roundup[TM] (Monsanto Company, St. Louis, Missouri). Because the crew had to carry out routine duties as well as the thistle control project, the spraying was done on Fridays, Saturdays, and a couple of Sundays, 10 hours each day, over eight weekends. Tidwell estimates that 2,500 to 3,000 acres of artichoke thistle were sprayed throughout the 17,000-acre burn area. Within weeks, the thistle plants were becoming flat clumps of dead, brown leaves.

Project officials consider this just the beginning of the habitat restoration. Large-scale spraying will be done for the next two years, thus allowing native plants to re-establish themselves. "By that time, the native populations should build up their numbers. Wherever we look at undisturbed chaparral, coastal sage brush or grasslands, the artichoke thistle can't get in," Pryor said.

A one percent cover of artichoke thistle is expected in succeeding years, and spot spraying will be used to control it.

Limited seeding and planting of native species will be done on large, flat areas. For the most part, the restoration is expected to occur naturally as native plant seeds are blown down by wind or washed down by rain from the slopes of the canyon hills. If all goes as planned, native bunchgrass will fill the grasslands; the coastal sage brush will come back with a resurgence of California sage, prickly pear cactus, coyote bush, and deer weed; and at higher elevations the chaparral will blossom with laurel sumac and sugar bush. Transition plants such as California buckwheat, monkey flower, and lemonade berry will flourish in both coastal sage brush and the chaparral.

Although the ash cover and charred vegetation gave the land a dead look after the fire, buried seeds and plant bulbs will bring the area back to life. "And natural soil features - the cracks, the little fissures, the worm holes, and the rodent holes - all help to aerate the ground and make it a healthy environment," Pryor added.

Officials learned from past attempts to control artichoke thistle in Orange County, Pryor said. "They tried burn plots; they tried different herbicides; they tried digging them out, chopping them off, and repeated cuttings. It always grew back."

But the future of the land looks good, Tidwell and Pryor agree. Cattle have not grazed in the area for more than a decade, and project officials believe the combination of the fire and the spraying have brought artichoke thistle under control. Pryor was impressed by Tidwell and his crew members. "They really have an environmental ethic," he said. "They eliminate the weeds, then they really get into rehabilitating the land to make it usable for local plant and animal species."

Said Tidwell, "We're starting the healing process, and it will heal quickly if we just give it a chance. All we have to do is tip the balance in our favor."
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Title Annotation:southern California
Publication:Public Works
Date:Mar 1, 1995
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