Itasca, Minnesota’s oldest state park, holds some of the country’s most pristine lakes and natural marvels. Visitors flock from all over the world to see one of the county’s primo sights—the upper portion of the Mississippi River.

It might sound idyllic, but the area has one major problem: It’s chock full of spotted knapweed, an exotic, invasive weed that chokes out native plants.

Due to the site’s environmentally sensitive nature, park officials chose an eco, albeit unusual, method of dealing with the problem—goats.

Last summer, park officials brought in goats to munch on the knapweed in the area. The animals, which are managed by a herder and provided by local farmers, spend about two weeks in July and August chomping on the weed. Last week marked the end of the second year of the three-year program, and park managers are already noticing some encouraging results.

“With goats, we’re changing the system and making it less desirable for exotics and more desirable for our native plants,” says Becky Marty, the coordinator of the goat program at the park. “We’ve seen a significant increase in grasses in the area. It looks like the knapweed is really being knocked back.”

Itasca is not alone in its endeavor to employ four-legged friends as natural weed controls. From the urban areas of Florida, across the ranges in Montana, to vineyards in California, environmentally conscious landowners and managers are increasingly turning to animals to control invasive weeds that are killing off native plants.

Here’s how it works: Land managers lease sheep or goats from nearby farmers, who truck the animals in and provide herders and electric fencing to contain the hoofed mowers. Once the sheep or goats chew their way through the weeds, the herders move the fences, and corral the animals into another area. Depending on the amount of vegetation and type of weed, it takes at least 100 goats to graze one acre a day, says Jason Garn, owner of D’Goat Ranch in Utah.

In order to really control the invasives, managers must bring the animals back to chew down the weeds during each flowering season. With each grazing, the weeds’ root systems get weaker and weaker.

“[Animals] take off the flowers and leaves, but they don’t take the stem of the plant, so the plant still thinks it’s alive,” says Marty.

“So it’s still pumping reserves up through the stem, which exhausts the root system.”

Controlling weeds with animal grazing is a less environmentally harmful alternative to chemical-laden herbicides. And as an added bonus, goats and sheep provide fertilizer and trample native seeds into the soil to promote growth.

But despite its eco-friendly attributes, some say animal grazing isn’t appropriate for all scenarios.

Rodney Kott, a sheep specialist at Montana State University’s Sheep Institute, promotes an integrated management approach—using animal grazing along with mechanical methods and some herbicides to control invasive weeds, which he says are the number one environmental problem in the Northwest. 

“Using animals to control weeds is a tool,” says John Hendrickson, a range scientist with the USDA’s Agricultural Research Service (ARS). “Where that tool actually fits depends on each individual situation.”

So far, grazing animals are predominately used to control weeds in rangelands. But that’s changing: Cities in Florida use sheep and goats to control kudzu, an invasive and rapid-growing vine; vineyards use animals to keep weeds in check that can harm grape vines; and communities across the US use goats to graze shrubs that create firebreaks.

Though managed grazing isn’t a mainstream form of weed control yet, experts are hopeful that the trend will continue to grow. Rachel Frost is currently conducting her post-doctoral research in animal and range sciences at Montana State University.

“I hope that grazing itself becomes more popular as it becomes recognized as a tool that can be used to improve the landscape in a very environmentally friendly fashion,” she says. “That’s what I’m basing my career on.”

Story by Sarah Parsons. This article originally appeared in "Plenty" in September 2007.

Copyright Environ Press 2007

Another kind of hoover
Land managers use animals to control weeds.