Master Gardener: Invasive weeds |

Master Gardener: Invasive weeds

Becky Edmiston
For Steamboat Pilot & Today
An invasive species, Whitetop is in bloom.
Dan Edmiston/courtesy

I’ve always been told a weed is any plant in a place you don’t want it. But to be considered an invasive weed it must be a nonnative plant that causes economic or ecological harm.  Well-adapted to our climate and soils with no natural enemies, invasive plants can form dense stands that out-compete natives. The effects of this competition include decreased forage for native and domestic herbivores, decreased pollinator forage and increased wildfire frequency.

Typically, it is large landowners who are economically impacted; either by the cost of mitigation or by the loss of forage for their livestock. Many don’t pay attention to the plants around us, let alone know what plants are native. It doesn’t help that some of our worst weeds were introduced as landscape plants and sold at nurseries.  

Federal, state and local governments have designated some of these weeds as noxious. To raise awareness of these weeds in Colorado, Gov. Jared Polis proclaimed May 16 to 23 as “Colorado Noxious Weed Awareness Week.” Check out

Whitetop (Cardaria draba) is so pervasive in my neighborhood that many may think it is native. The unassuming small white flowers could be mistaken as a nice addition to a flower bed. This weed is already blooming in the west part of the county and will bloom in Steamboat Springs in coming weeks.  Its presence along the Emerald Mountain trails has increased markedly in the past several years. Each prolific plant will produce up to 5,000 seeds ready to set up residence. 

Master Gardener: For more

Colorado State University Master Gardeners are available to answer your gardening questions. Email or call the CSU Extension office at 970-879-0825 and ask to leave a message for the Master Gardeners. Thursday morning office hours and scheduled site visits are currently suspended.

In this battle, prevention is the best medicine. Invasive plants, including whitetop, move into disturbed areas making your best defense a good offense. You need to get soil covered as soon as possible following construction, landscaping or trail building, before invasive weeds can get a foothold. This is the most cost-effective method of control.  

Many invasives are easier to remove as seedlings and may be more susceptible to herbicides. Remember, these plants are invasive because they are great at reproducing. If you put off mitigation by a year, a few weeds can become many, and even worse. On a town lot, mitigation might be as simple as hand-pulling weeds or keeping invasives from going to seed by mowing. If you choose to use chemical controls, strictly follow the application instructions (for safety and effectiveness) and be careful not to kill plants you want to keep.

Have questions on weed ID or control? Contact the Master Gardeners.

Becky Edmiston was in the 2018 Colorado Master Gardener class and is a professor of biology and teaches permaculture design at Colorado Mountain College Steamboat Springs. She leads the Routt County Beekeeping Association and the CMC beekeeping club.

Young whitetop coming in is an invasive species.
Dan Edmiston/courtesy

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