Thistle management - Ask Extension
Location: Steamboat Springs: Site work disturbed the original ground; thistle weeds have grown back first. How do I kill the thistle plants and k...
Knowledgebase
Thistle management #870394
Asked May 28, 2024, 11:22 AM EDT
Location: Steamboat Springs: Site work disturbed the original ground; thistle weeds have grown back first. How do I kill the thistle plants and keep them from coming back?
Routt County Colorado
Expert Response
Hi Scott-
Anytime one disturbs the soil there is a good chance weeds will come up...for several reasons. The number one reason is that the ground cover that was there (ie: plants covering the ground) aren't, which gives other plants an opportunity to grow. The second is that there are seeds already in the soil that have laid dormant for some period of time; this is referred to as the 'soil seed bank.' Exposing those seeds by bringing them nearer to the surface allows them to germinate and grow.
Why is this important? It means that it's not just about killing the plants you see now, but continuing to monitor and control the weeds for quite some time until other, more desirable plants are there; and these thistles will likely continue to come up for a number of growing seasons, even with the planting/growth of other, desirable plants.
If the disturbed area is in a residential area or area that will be landscaped soon, you will have to use a product that is labeled for such an area. Such products would include a mix of herbicides that may include 2, 4-D, Dicamba, and MCPA, like Weed Clear; another option would be glyphosate, like in the original formulation of Round-Up. Note that this is assuming this is Canada thistle which is coming up; as a rhizomatous perennial, it is best to spray Canada thistle, although if you feel like these really are first-year seedlings, pulling them and/or digging them up are just as effective. If it is a bull or musk thistle, digging is a great way to take care of them.
If the disturbed area is agricultural, please refer to CSU Fact Sheet 3.108, LINKED HERE. If it is a construction or range site, you might use an aminopyralid herbicide, like Milestone.
Note that as mentioned above, getting desirable plants to grow in the area is paramount if want long-term results. That means you need to make a plan to seed the area soon so you can get these plants growing (would have been best to do it a couple of weeks ago, but hindsight is 20/20). Please READ THE LABEL for any of the herbicides you might use to ensure seeding and/or planting is not impacted negatively by their use. Because it likely will be an issue, using glyphosate and spraying the area is probably going to be best as you can plant seed or plants soon thereafter; you can use the other products to selectively spray the thistle well-after the 'good plants' have become established, which again will be outlined on the herbicide label.
I hope this all makes sense. Let me know if you have further quesitons.
Todd
Anytime one disturbs the soil there is a good chance weeds will come up...for several reasons. The number one reason is that the ground cover that was there (ie: plants covering the ground) aren't, which gives other plants an opportunity to grow. The second is that there are seeds already in the soil that have laid dormant for some period of time; this is referred to as the 'soil seed bank.' Exposing those seeds by bringing them nearer to the surface allows them to germinate and grow.
Why is this important? It means that it's not just about killing the plants you see now, but continuing to monitor and control the weeds for quite some time until other, more desirable plants are there; and these thistles will likely continue to come up for a number of growing seasons, even with the planting/growth of other, desirable plants.
If the disturbed area is in a residential area or area that will be landscaped soon, you will have to use a product that is labeled for such an area. Such products would include a mix of herbicides that may include 2, 4-D, Dicamba, and MCPA, like Weed Clear; another option would be glyphosate, like in the original formulation of Round-Up. Note that this is assuming this is Canada thistle which is coming up; as a rhizomatous perennial, it is best to spray Canada thistle, although if you feel like these really are first-year seedlings, pulling them and/or digging them up are just as effective. If it is a bull or musk thistle, digging is a great way to take care of them.
If the disturbed area is agricultural, please refer to CSU Fact Sheet 3.108, LINKED HERE. If it is a construction or range site, you might use an aminopyralid herbicide, like Milestone.
Note that as mentioned above, getting desirable plants to grow in the area is paramount if want long-term results. That means you need to make a plan to seed the area soon so you can get these plants growing (would have been best to do it a couple of weeks ago, but hindsight is 20/20). Please READ THE LABEL for any of the herbicides you might use to ensure seeding and/or planting is not impacted negatively by their use. Because it likely will be an issue, using glyphosate and spraying the area is probably going to be best as you can plant seed or plants soon thereafter; you can use the other products to selectively spray the thistle well-after the 'good plants' have become established, which again will be outlined on the herbicide label.
I hope this all makes sense. Let me know if you have further quesitons.
Todd
