by Elizabeth Miller
Goats,the notoriously undiscriminating eaters, have been set loose on some of Boulder’s non-irrigated park areas to assist the City of Boulder in controlling invasive weeds.
The city has allowed 300 to 350 goats to graze on the east side of the Boulder Reservoir for about a week.
This is the 11th consecutive year the Boulder’s Parks and Recreation Department has sent goats out to patrol the weed populations as part of an integrated pest management plan. Integrated pest management means tackling a pest through several methods — cultural, mechanical, chemical and biological. In a backyard garden, it could mean releasing ladybugs to eat aphids.
“The use of biological controls, such as goat-grazing, is important as the department seeks to reduce the amount of herbicides used,” a city press release states.
According to the Samuel Roberts Noble Foundation, an independent, nonprofit institute in Oklahoma that studies plant science and agricultural programs, goats provide a lower-cost, if slower, alternative to mechanical or chemical weed control measures.
Research at the Noble Foundation indicates that goats prefer brush and broad-leafed, non-grassy plants — weeds, generally. They go for woody or broad-leafed plants 85 percent of the time, and grasses only 13 percent of the time. Goats also browse, rather than graze, nibbling bits from several plants, which is how they get away with eating toxic weeds without getting poisoned.
Some of the plants goats might eat appear on Colorado’s list of noxious weeds. The state requires the monitoring and control of those species.
“When done at the proper times, grazing prevents the current year´s plants from going to seed and depletes the root system´s reserves,” according to the city. “Grazing also recycles organic material back into the soil and cultivates the ground, allowing for better water infiltration, aeration and sunlight exposure.”
Relatively few counties have adopted goats for integrated pest management, according to Steve Ryder, state weed coordinator with the Colorado Department of Agriculture.
“They’ve looked into it and found … for a number of reasons they may not be able to take advantage of them,” Ryder says. “One of them is cost.”
Goats aren’t expensive; it’s the labor necessary to pen them close to the weeds they graze that’s expensive.
“Goats will graze on anything, and they like native grasses and forbs just as much, if not more than, noxious weeds,” he says. “You have to be really hands-on with them and make sure they’re eating what you want them to eat.”
Browsing goats work basically like a lawn mower, he says, by pruning the plant back without destroying its root system. State requirements on weeds divide them into three categories, called “lists,” with varying levels of priority for eradication.
Neither eradicating nor stopping the spread of the weeds on List C is a priority, though the state and local government will provide education and resources to groups that want to require control of those species. List B species are widespread; controlling infestations is an immediate goal, while eradication is a long-term goal. For List A noxious weeds, which are not well established in the state yet and are very invasive, the state requires eradication.
“Unfortunately Boulder County has probably more List A species than any other county in the state,” Ryder says. “The combination of suburban and urban areas, prairie and mountain micro-climates has made the area particularly susceptible.”
Grazing doesn’t always keep a plant species from establishing itself, he says, because the plant has to be prevented from going to seed. Mow it — or graze it — down one week, and it could re-flower and produce viable seeds a few weeks later.