Centaurea solstitalis creeps across the foothills above Utah Valley, snuffing as much natural vegetation as a raging fire. Only no one really notices because it strikes without smoke or flames.

But the consequences are just as devastating.

The thorny, blue-green weed with a bright yellow flower, commonly known as yellow starthistle, rapidly chokes out native plants and disrupts delicate ecosystems. Horses that munch on it can get a potentially fatal nervous disorder called chewing disease.

Uinta National Forest ecologist Denise Van Keuren calls the non-native plant the "poster child" of noxious weeds. "It's the weed that sneaks up on you."

An army of botanical rebels is stealthily ravaging the Wasatch Mountains.

Non-native grasses and plants, including some disguised as pretty wildflowers, mount perennial search-and-destroy missions in the foothills and forests.

"Weeds do act as a biological wildfire," said Van Keuren, standing in the shade of a non-native Siberian elm in the foothills above Pleasant Grove. "They eat up everything."

Noxious weeds are one of four land management issues the U.S. Forest Service says are wreaking havoc in the national forests on the Wasatch Range. Habitat fragmentation, unmanaged recreation and overgrown, unhealthy vegetation — prime fuel for fires in this drought-stricken region — are the others.

Seeds that sprout into noxious weeds find their way into the mountains in a variety of ways. The wind blows them in. Horses or cattle carry them on their hooves or hair. All-terrain vehicles transport them on mud-encrusted undercarriages.

"It's not that people are being belligerent," said Dave Palazzolo, Uinta National Forest spokesman. "They just don't know what they're doing."

Even the Forest Service has contributed to the problem. Trucks called in to fight forest fires are often seed carriers. "Big fire camps have big weed problems," Van Keuren said. Foresters are now required to give their vehicles a thorough washing to avoid spreading weeds.

Utah State University Extension suggests the defense for noxious weeds be the same as for wildfires: prevention, detection and suppression. Because herbicides are expensive, the Forest Service relies on volunteers to fight the invaders using hand-to-weed combat.

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