The New Pilgrims: Noxious Weeds in Ouray County
by Christina Callicott
Jul 22, 2008 | 1128 views | 0 0 comments | 9 9 recommendations | email to a friend | print
Invasive Species Threaten Native Ecology, Economy

This is the first installment in a two-part series on weeds in Ouray County. Stay tuned next month for a story on weed control, including a discussion of non-toxic and biological measures.


OURAY COUNTY – Two years ago you could still buy a Russian olive tree in the local nurseries. That was despite the fact that the tree is considered a noxious weed by the state, one of many plant species designated for eradication, containment or control due to the negative impacts it has on the ecology and the economy.

The recent availability of the Russian olive highlights one of the problems that County Weed Manager Ron Mabry faces in his mission to control these weeds: many of them were, and still are, considered desirable plants, and many people simply aren’t aware of the problems with noxious weeds.

Here’s the skinny: The Colorado Noxious Weed Act was passed in 1996, and defines noxious weeds as non-native species that have certain negative impacts on crops, native plant populations, livestock, and the management of natural or agricultural systems. The act prioritized the plants into three lists, with the A list being designated for eradication and the B list being designated for containment. C-list species such as common burdock are a lower priority.

Most of the invasive weeds in Ouray County are B-list species, Mabry said. He said that field bindweed, a fast growing vine with a small, white morning-glory type flower that makes itself imperturbably at home throughout Ouray County, is on the C list. “That’s one we’ll have to learn to live with,” Mabry said. Mabry said the fast-spreading and damaging weed is on the C list probably because “they know we’ll never get rid of it.”

According to the booklet Troublesome Weeds of the Rocky Mountain West, prepared by the Colorado Weed Management Association, “Biodiversity and ecosystem stability are threatened by noxious weeds. A common characteristic of all noxious weeds is their aggressive, competitive behavior.” Invasive plants, lacking the natural checks and balances of their native ecosystem, tend to crowd out native vegetation and alter plant communities and soil structures. Animal species that co-evolved with native ecosystems “cannot readily adapt to rapid changes in these plant communities caused by noxious weeds,” according to the booklet.

In other cases, noxious weeds are a direct threat to ranch and farm economies and to natural resources. Tamarisk, a well known invasive that has colonized long stretches of the Colorado and Green rivers and many of their tributaries, depletes water tables due to its voracious thirst and expansive growth habits.

Noxious weeds can be introduced to an area intentionally, as an ornamental plant for the yard or garden, or unintentionally, as a stowaway on the socks and shoes of a hiker, imbedded in the fur coat of an animal, carried by a car’s tires, or bound up in a load of contaminated hay or straw or even road-bed gravel.

“Probably 40 percent of our invasive weeds are escaped ornamentals,” Mabry said. He said that every spring, he visits local nurseries to check their wildflower seed packets and make sure that they aren’t unintentionally selling mixes that contain invasives such as dame’s rocket and oxeye daisy. He said that a population of dame’s rocket on Log Hill was introduced by a Virginia couple who transplanted it from their home there. “In Virginia, it’s OK,” he said, “but in Colorado, it’s not.”

Oxeye daisy is a B-list species common from Billy Creek, along the Uncompahgre and throughout the Cow Creek drainage, up as far as Crystal Lake on Ophir Pass. It’s found regularly in the high country, where Ouray County’s famous wildflowers live. It’s also an attractive plant that some people like having around. “The Town of Ouray should name it their town flower,” Mabry said.

Town of Ouray Weed Coordinator Peg Foster agreed. “A lot of people around here don’t feel the oxeye daisy is a noxious weed,” she said. “They’d rather have a whole hillside of that than something else.”

On the other hand, Mabry said that a large population of leafy spurge, a B-list species, on Miller Mesa dates from about 1955, when a Hollywood film crew brought in a load of hay from Montana that was contaminated with the weed.

“It thrived and spread all over,” Mabry said. “Now it’s come down the drainages and down the river into the town of Ridgway. There’s even a patch in the state park. The biggest problem is that it’s all on private property, and getting landowners to cooperate is a challenge.”

According to both state and county law, responsibility for eradicating and controlling listed weeds falls with the property owner.

When he finds listed weeds on private property, Mabry sends out letters notifying the property owners of their responsibilities. If the landowner doesn’t respond within 10 days with action or with a plan, “then we can by law go on your property and treat the weeds ourselves. We bill you for the cost plus 20 percent, and then it becomes a primary lien on your property and gets added to your tax bill. But I have never done that. I’d rather get people’s cooperation.” Mabry said that out of 400 letters he sent regarding a newly listed plant called absinthe wormwood, once mistaken for sagebrush, he got four responses. “And two of them said they didn’t think they had it.”

With a changing climate, heavy traffic into previously remote areas, and other disturbances to the ecology, some think the weeds will have their way. But Mabry remains cautiously optimistic.

“There’s times you want to throw your hands up and just say it’s too late,” he said. “But I still think we have small enough populations here in Ouray County that we can make a difference. I still don’t think people understand what the impacts of these invasives are. I’m willing to do what it takes to get people on board.”

Information on invasive weed species, including pictures for identification, is available on the Internet. Copies of Troublesome Weeds of the Rocky Mountain West are available for $3.50 at Mabry’s office in the County Land Use Office, 111 Mall Road, Ridgway. Contact Mabry at 970/626-5391 x23 for more information.
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