JACKSON, Wyo. — It’s the middle of summer and wildflowers are in bloom, but unfortunately so are invasive plants, and Teton County Weed and Pest District (TCWP) is reminding people that now is the prime time to control them.
When invasive species take over, native plants that animals rely on for food get boxed out. Some invasive plants are also dangerous because they’re poisonous to wildlife.
“Plants are bolting and some of them are going to flower, which means that they are getting very close to, if not already, producing seeds for the year,” Lesley Beckworth, Outreach Coordinator at TCWP tells Buckrail.
This means it’s an ideal time to kill these non-native species to make sure their seeds don’t spread.
While invasive plants can be pretty, they tend to spread easily, with some seed pods producing up to 200,000 seeds.
“They are rapid and aggressive spreaders and will create monocultures so that other species can’t grow,” Beckworth says.
To get rid of most invasive species, Beckworth recommends chopping them down, collecting the flower heads to contain the seeds and spraying the roots with herbicide.
Land owners who aren’t sure of which plants to eradicate can visit TCWP’s website to submit a photo of the species on their property to properly identify it, or use the website’s guide to invasive plants. TCWP will also send someone out for a free consultation to help come up with a plant management plan.
While several invasive species have spread through developed areas in Jackson Hole, Beckworth notes that the parks are still free of many of these intruders. In order to keep it that way, people should remember the rule, “play, clean and go.” This means play in and enjoy a wilderness area, and then clean shoes and brush pets or horses to make sure no seeds have hitchhiked their way out and might get a ride to the next recreation destination.
Here are some of the dominant invasive species to look out for and control this time of year:
Spotted knapweed
Spotted knapweed has a cluster of leaves at its base that look much like dandelion leaves. Its bloom is purple with spiky-looking petals. Knapweed is biennial, growing for two years. In the first year it grows a taproot and a three-foot main stem that’s usually branched near or above the base, giving the plant a bushy appearance. Smaller infestations of knapweed can be controlled by uprooting the plant and collecting flower heads. Larger ones can be treated with herbicide.
Dalmation toadflax
Dalmation toadflax is a perennial species that usually produces an erect stem about three feet tall. Flowers are yellow and are clustered along the upper length of the stem. The stem itself is woody at the base and waxy toward the top. Flowers are between 3/4 and 1 1/2 inches long and have an upper and lower “lip,” with a long spur at the bottom. Dalmation toadflax can be controlled by pulling the plant out of the ground if it’s in cobble or loose soil, but it’s important to make sure all of the root system is removed. If hand removal isn’t possible or the infestation is large, herbicide should be used.
Canada thistle
Canada thistle is a perennial member of the daisy/aster family. Its stems are smooth or slightly hairy and reach three to five feet. Flowers come in clusters at the ends of the stems and branches, and range from light pink to deep purple or occasionally white. Petals protrude from a round bulb. This thistle has an extensive underground root system, much like an aspen grove. Because of this, digging up by hand is not recommended, and an herbicide should be used. If the plant has bolted, or grown seeds, chop off and collect the flower heads.
Other thistles to look out for are the musk thistle and bull thistle, which are both biennial and bloom in their second years of growth, according to Beckworth.
People should make sure they’re using the right herbicide before spraying invasive plants, as different chemicals are safe for different areas, Beckworth notes. What’s good for a lawn won’t necessarily be good for a pasture or natural area.
