Knapweed is one of the nastiest noxious weeds in Routt County.
Deb Babcock's gardening column appears Mondays in Steamboat Today.
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Steamboat Springs There’s an old gardening saying that a weed is only a weed when it’s in a place where you don’t want it. However, in the case of several noxious weeds in the Yampa Valley — some of which have beautiful flowers — it’s a weed wherever it grows.
That’s because weeds identified as noxious for Routt County harm our environment. They tend to spread fast, taking over native vegetation that is important for the support of livestock, wild animals and erosion control, among other benefits. Even if this pretty plant is located in a homeowner’s garden where you can keep an eye on it, the pollen, seeds and root system can escape into the environment and end up ruining a meadow, hayfield or stream bank.
Knapweed is one of the nastiest noxious weeds in Routt County, and there are four kinds we need to try and eliminate: Russian, meadow, diffused and spotted varieties.
Russian knapweed found its way to our part of the country in a load of hay. It reproduces by seed and by a creeping root system. It will grow to 3 feet tall and features lavender and white flowers. This weed is easily identified by its root system — the only one with black roots. It has started flowering and will continue to do so through August.
The one we see the most often here is diffused knapweed, which grows in dry areas along the road and on land where livestock feed. At its peak, it features a stem as high as 2 feet, which branches near the top and produces small white or purple flowers with bracts ending in sharp spines. You should see it flowering just about this time of year through September.
Meadow knapweed is found primarily in the area where the hot springs joins the Elk River along Routt County Road 129 in North Routt. It features large pink and purplish-red flowers and grows as high as 3.5 feet tall.
Finally, spotted knapweed is the fourth of this group of noxious weeds. It grows to 3 feet tall and features a lavender to purple thistle-like flower. It first appeared in Routt County along trench lines dug up for fiber optic cable in the county.
Controlling knapweed requires multiple offensives to stress it until it dies. This includes trying to dig up the deep roots as best as you can, using a chemical control such as 2,4-D, Escort or Curtail (use according to label directions), and reseeding the areas where the weed has been eradicated with a suitable grass mixture so the weed won’t come back.
Although we probably cannot completely eradicate this noxious weed, each of us can do our part to keep it from spreading further by identifying it on our own properties and taking steps to make sure it won’t grow and spread further.
Deb Babcock is a master gardener through the Routt County Extension Office. If you have any questions, call 970-879-0825.