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By Kirstin Mosbruger, Salt Lake County Noxious Weed Intern

It’s that time of year when Salt Lake County’s mountainsides erupt with wildflowers. Everywhere you look, there are gorgeous blooms painting the hillsides in yellows, blues and oranges, and unfortunately, in the foothills of the Wasatch Range, there are also abundant purples.


Why is purple unfortunate? Because many of the purple flowers that we might assume are wildflowers are not actually meant to be in Utah at all. They are not native, and they are rapidly taking over. Houndstongue, Scotch thistle, musk thistle, Canada thistle, and money plant are among the purple wildflowers listed as noxious and invasive weeds on the State of Utah noxious weeds list. Dame’s rocket (Hesperis matronalis) is another purple flower on the list; it has recently appeared in Emigration Canyon, and it appears to be spreading.

Wildlife doesn’t forage on these invaders. Our native plants often can’t compete with them for resources. Quite a few of these non-native plants have evolved features that are downright harmful. Many of us have had the misfortune of puncturing the sole of a foot or a bike tire on the sharp spines of a goathead (Tribulus terrestris). Myrtle spurge (Euphorbia myrsinites) contains caustic latex sap that can cause skin lesions and even blindness.

But those two noxious weed examples have yellow flowers. Dame’s rocket lacks the spines, latex sap, or prickles of other noxious weeds, but it nonetheless is damaging to our ecosystem and will spread without our help. It goes by many names: dame’s violet, mother-of-the-evening, sweet rocket; all very heart-warming. You may have gazed upon dense stands of it as you drove up one of the canyons. It has a beautiful purple flower, and it smells heavenly. It’s so pretty that nurseries across the country are still selling it in wildflower seed mixes, in spite of it being banned as a noxious weed.

How could such a gorgeous plant be bad? Dame’s rocket is allelopathic, meaning it has the ability to release toxins into the soil that prohibit other plants from growing around it. It kills all other plants to make room for more dame’s rocket, and steadily, it creates a monoculture where no other plant exists.


What’s wrong with a monoculture? No healthy ecosystem can survive when just one plant exists within it. We need an abundance and variety of plant life to support the many species that rely upon it. As native plants get pushed out, so does wildlife. Our beautiful, vibrant wilderness quickly gets swallowed up by a killer plant that only blooms for a few short weeks, then just sits there, not contributing anything to society. And slowly killing everything else around it.

So, what can you do about it? Don’t buy wildflower seeds that contain dame’s rocket. Don’t plant it, and don’t allow it to grow in your yard if it’s already growing there. Tell your neighbors about it and help them get rid of theirs too. If you see it in natural spaces, contact the Salt Lake County Noxious Weed Program and let us know, so that we can work with the landowner to get it controlled. It’s not too late to keep this invader from taking over, but we need your help in this fight. Keep our natural spaces full of native Utah flowers, and keep our unique landscapes healthy for generations to enjoy for years to come.

For more information on noxious weeds, including management, visit

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