Invasive Grass Mitigation - Ask Extension
I live in Steamboat Springs and my gardens are getting extremely overwhelmed by grass in the spring. I would like to kill the grass, but keep perennia...
Knowledgebase
Invasive Grass Mitigation #927904
Asked April 09, 2026, 10:58 AM EDT
I live in Steamboat Springs and my gardens are getting extremely overwhelmed by grass in the spring. I would like to kill the grass, but keep perennials alive. Is there a spray or another method that you would recommend?
Routt County Colorado
Expert Response
Good morning, Kelly-
Grass in flower beds is always a challenge, especially if you have a sod-forming grass in your beds because it will continue to spread and the roots will 'mingle' with the roots of your desirable plants. Hand pulling is a great option, but I understand the challenges of that, too.
The application of a non-selective, translocating herbicide, such as glyphosate, can be effective IF you're careful not to get it on your other plants. Using a spounge, a small paintbrush, or by placing a toilet paper roll over the grass and spraying directly into it (thus directing the herbicide to only the grass plant) can be effective. Some of the grasses growing 'in' the plants will continue to grow, however, and that's problematic. Note that you can use 'burn down' or contact herbicides in this way, too, (like horticultural vinegar) but will only kill the living material it touches and will not kill the roots or entire plant.
There is a selective grass killer that may prove very useful in your situation. Look for herbicides with the active ingredient of Fluazifop-P-butyl, which works by limiting lipid synthesis in the plant. Because of its mode of action, you won't see results right away, but within 2-3 weeks, most of the grass should be drying up...and your ornamentals should be fine. You may find it under the Ortho Grass B Gon label or any similar product that says 'Grass Killer' on the label. Make sure to look at the active ingredient, however.
As with any application of a pesticide, make sure to follow the labeled application rates, timing, site limitations, etc. and wear the correct protective clothing. I would also start using it in a limited area and not apply it fully to your garden until you confirm that you're not seeing any damage to your desirable plants. Given our early spring and lack of moisture, some plants that would be fine with this product may react differently this year.
Let me know if you have other questions and feel free to contact me directly at our local office.
Grass in flower beds is always a challenge, especially if you have a sod-forming grass in your beds because it will continue to spread and the roots will 'mingle' with the roots of your desirable plants. Hand pulling is a great option, but I understand the challenges of that, too.
The application of a non-selective, translocating herbicide, such as glyphosate, can be effective IF you're careful not to get it on your other plants. Using a spounge, a small paintbrush, or by placing a toilet paper roll over the grass and spraying directly into it (thus directing the herbicide to only the grass plant) can be effective. Some of the grasses growing 'in' the plants will continue to grow, however, and that's problematic. Note that you can use 'burn down' or contact herbicides in this way, too, (like horticultural vinegar) but will only kill the living material it touches and will not kill the roots or entire plant.
There is a selective grass killer that may prove very useful in your situation. Look for herbicides with the active ingredient of Fluazifop-P-butyl, which works by limiting lipid synthesis in the plant. Because of its mode of action, you won't see results right away, but within 2-3 weeks, most of the grass should be drying up...and your ornamentals should be fine. You may find it under the Ortho Grass B Gon label or any similar product that says 'Grass Killer' on the label. Make sure to look at the active ingredient, however.
As with any application of a pesticide, make sure to follow the labeled application rates, timing, site limitations, etc. and wear the correct protective clothing. I would also start using it in a limited area and not apply it fully to your garden until you confirm that you're not seeing any damage to your desirable plants. Given our early spring and lack of moisture, some plants that would be fine with this product may react differently this year.
Let me know if you have other questions and feel free to contact me directly at our local office.
Thank you Todd!
