Pine Bluffs Post - Serving all of Eastern Laramie County since 1908

Dalmatian Toadflax - Scourge of the Plains


February 28, 2019

Photo Courtesy of Mike Heath

Cheyenne Botanical Gardens crevice garden in winter time.

About seventeen years or so ago, I was visiting a neighbor and noticed a very pretty yellow flower in the draw behind his house. I took a closer look at the plant and considered asking if I could dig some up to bring home. I never did and, unfortunately, I learned later that I didn't have to. It came all on its own. Now, my little piece of paradise is covered in Dalmatian Toadflax.

I only learned what the plant was about five years ago. All I knew up to that point is that is seemed to be taking over in my windbreak as well as the pasture. More and more was showing up every year. In fact, there were some places just east of Cheyenne where the lots have been completely covered in toadflax. All I knew at the time was that I needed to find out more about it...and how to get rid of it.

As I started digging into this extremely invasive and devastating plant, I found nothing that was good. Dalmatian Toadflax, or Broadleaf Toadflax, is native to the Mediterranean region. It was brought to the United States in the late `1800's as an ornamental plant and for use in fabric dyes. It was believed to have limited use in folk medicine. Since being introduced it has spread across nearly the entire United States with the exception of the southern and southeastern states. The plant is highly competitive with native species and will eventually crowd out native plants if left uncontrolled. Dalmatian Toadflax has been designated as a noxious weed in nine western states and three western Canadian provinces. It's cousin, the Yellow Toadflax, is equally as invasive, but to a different habitat. It has spread to every state and throughout Canada. Dalmatian Toadflax mostly invades disrupted, overgrazed and degraded lands; abandoned lots; open fields; etc. while Yellow Toadflax prefers more moist and fertile conditions. It will also grow at higher altitudes and is more likely to affect cropland. Together, they represent a serious threat to all of our land. By crowding out native plants in pastures, they reduce the forage for cattle and horses. In fact, they contain elements that are toxic to cattle and horses. By invading cropland, they reduce the nutrients in the soil that are needed by the crops, thereby reducing the viability of the land available to grow our food. Mostly what we've seen in Laramie County is the Dalmatian Toadflax.

The plant has proven to be very difficult to control. With its waxy leaves, herbicides haven't proven to be especially effective. Some sulfonylurea and phenoxy herbicides have shown some benefit if they're used with a non-ionic surfactant to break down the wax on the leaves. But even this has been only mildly effective. With a small infestation, pulling the young plants can be beneficial. Although, older plants will just snap off and leave the root in the ground. Since the plants grows from both seeds and roots it just means that a new plant will soon be sprouting. By the way, each plant can produce over a half million seeds. Mowing will reduce the number of seeds and will help if it kept up for several years. I tried this the last few years and found it to be a lot of trouble since new plants were sprouting faster than I could keep the pasture mowed. Constant plowing has shown some promise if its kept up but it leaves pieces of cut up roots in the ground to regrow. It would take several years of plowing to get rid of the plant. Not only does constant plowing disrupt the ecosystem of the ground, but the land would be completely non-productive during the period it's being plowed and the resulting dustbowl would simply blow away during the Wyoming Wind Festival. Which, by the way, occurs from January 1st through December 31st every year. That's not a very good option. So, what is left.

Fortunately, there are some biological control agents that were brought in with the toadflax imported from eastern Europe. Two flower-eating weevils were discovered in New York in the 1920's. Since then, ten more have been introduced and approved for use in controlling toadflax, including one defoliating moth. Shortly before I learned what toadflax was, another neighbor was working with the USDA on testing one of the weevils for use here in Laramie County. They originally intended using the weevil on her property, but she didn't have enough of an infestation to be a viable test, but I did. When they asked I was happy to let them release the weevils in my windbreak which is where the heaviest infestation was, and still is today. Even though the weevils had no effect on the toadflax, we did learn a few things. They don't work in just one year. That's not a great surprise. The problem became survival. The weevils need to overwinter in a protected location. That's hard to find out here on the plains. Since they'll live inside the stems of the toadflax plants, they need to be sheltered from the wind and cold. Toadflax doesn't necessarily live in sheltered areas. We proved to be a difficult location for the weevils to survive, but they may work better with a mild winter or if the property owner wanted to purchase a new batch of weevils every year to keep up the fight. I wanted something easier.

Photo Courtesy of Mike Heath

We purchased three goats with the hope they would eat the plants. This will be their second summer with us. Last year they were let out on the pasture in early summer so the toadflax had already germinated and had a good head start. But they went to work right away. By then the goats had a large variety of vegetation to munch on so the toadflax was only one plant of many. What I observed is that as the goats were walking around the pasture, they would nip off the tops of the plants and munch while they walked. One of the goats, Goliath, would stop and eat an entire plant while they other two, Davy and Samson, would only eat the tender tops. To my delight, they did eat the plants down more than I had expected. This year, they are already on the pasture. Since toadflax is one of the first plants to come up in the spring, my hope is that they'll be hungry enough for fresh green plants that they'll start nipping right away.

Controlling toadflax isn't easy. At this point, it's best to contact the Laramie County Conservation District for help. Rex Lockman with the district will being giving short classes on Dalmatian Toadflax at the Home and Garden Show on April 13th and at the Master Gardener's Mother's Day Plant Sale on May 11th. That would be a good place to start in our mutual fight to control this highly invasive and noxious weed. Unless we get it under control, it has the potential to devastate our pastures and farm ground. Let's band together and control this beast. If you have questions about this or any other horticultural topic, ask a Master Gardener. It's what we do.


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