Managing Non-native Cool Season Grasses

Is Burning a Possibility?

Burning will not kill non-native cool season grasses (CSG). It stimulates its growth because it opens the land to light and the warming sun. Since CSG are the first to pop out in spring, they will reap the benefits of this.



What about Burning Late in the Spring?

Frankly, there are no pros for this.

  • Reptiles and amphibians are out and could be harmed/killed
  • Insects that are immobile or slow fliers could be killed
  • Mammals can always be in jeopardy if the burn technique it to ring it

What Does Work?

Mowing Sections

Work in sections with this technique. Decide you will mow the worst 3 of 10 areas (as an example) in year 1, then deal with 4-6 in year 2, and 7-10 in year 3.

Mow sections when the grass is tillering will set the grass back – this is when the grass is 4-6” tall although this differs with the species you are dealing with. This is typically in late May/early June but check the grass and not the calendar.

Overseed with native short grasses (aka bunchgrasses) as they only need 70 degrees to germinate – do this before a rain. I prefer not to use the tallgrasses as they are very aggressive.

You will want to mow these sections again – maybe in early July. This will allow the sunlight to get to those seeds you tossed out a couple months ago.

Herbicide Sections

Broadcast spraying the entire ecosystem with grass-specific herbicide after an early burn to kill non-native CSG hasn’t been very effective. And it comes with high collateral damage to early growing grasses, such as junegrass (Koehleria macrantha).

I have found herbiciding sections (rather than the whole habitat area) with grass-specific herbicide to be effective. This can be done after a burn or a mowing once the CSG has had time to regrow.

Plan to overseed but wait for 30 days before doing so. This will give the herbicide time to reduce its residual in the soil.

You’ll want to check in early July to see if mowing is necessary. You’ll know by how much regrowth there might be. 

Sections can be herbicided prior to a fall burn. To prepare for this, mow in July/Aug and let it regrow to 4-6” and then herbicide it. You can overseed it afterwards and before the burn as well, just sow the seeds prior to a rain and about 30 days after the herbicide treatment.

Mowed sections of the remnant for CSG control
One section of mowed CSG

Photo on the right is an overview of our remnant where I mowed the CSG clones. The photo above is a close up of one of these mowed areas.