Zoysia Grass - Lawn Turns Yellow in the Fall
Dormant Zoysia Grass
QUESTION: My grass turned yellow in the fall. I am not sure the type of grass, but this is the second year in the grass has turned yellow. It is an established lawn for over 25 years. I had a soil test performed, The Phosphorus and Magnesium levels are optimum, the Potassium is below optimum (53ppm). Should I kill the existing grass and reseed or is there a better solution?
It sounds like you have a Zoysia grass lawn. Zoysia grass has been touted in the past as "the miracle lawn" for the mid-west. Zoysia is a warm-season grass. Warm-season grasses thrive in the summer heat and go dormant, turning brown/yellow in the fall. See this link for more information on zoysia: Zoysia Grass
You have a couple of options:
1. Kill the existing grass with a non-selective herbicide such as 41% glyphosate (which is Roundup - but look for the generic brands, they are much cheaper). Then seed it with a slit-seeder.
2. The strip the existing grass with a sod cutter and then re-sod with Kentucky bluegrass.
3. Over-seed the zoysia with a perennial ryegrass/Kentcuky bluegrass seed blend in the fall. Over-seeding will not get rid of the zoysia however it will keep it green over the winter.