How To Care For Cool Season Lawns In Minnesota During The Summer Heat

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Once temperatures get into the 80s and above, lawns will begin to struggle a little, with cool-season grasses having the hardest time. Growth will slow, color may fade, and lawns will show signs of wear and tear as they are less able to recover from stress and traffic. Some cool-season lawns will even go dormant in the summer, looking brown and brittle until early fall.

Water Wisely

  • Lawns need at least one inch of water per week, and more when the heat is severe. Use a rain gauge or straight-sided can to keep track of the amount of water received from rainfall and irrigation.
  • Water deeply and less frequently to encourage drought-tolerant roots.
  • Water early in the day to reduce evaporation and fungal growth.
  • Either water your lawn regularly and deeply, or don’t water at all. Don’t let your lawn go brown and dormant, then try to “water it back to life.” If your lawn goes dormant in summer, it should stay that way until fall – don’t worry, it should recover once the weather changes.

Mowing Tips

  • Raise your mower blade in the summer. Taller grass is more drought-tolerant, grows deeper roots, and helps shade the earth to prevent weed seeds from germinating. Cool-season grasses should be mowed at 3”- 4” during the summer, or as high as your blade will go, while warm-season grasses should be mowed at 2”- 3”.
  • Mulching grass clippings helps keep moisture levels steady.
  • Mow regularly, to prevent cutting more than 1/3 of the grass blade at a time. This keeps your grass healthier and prevents the clippings from smothering the grass.
  • Keep mower blades sharp. Make sure your mower is cutting your grass, not tearing it, to minimize stress during hot temperatures.

Don’t Over Fertilize

If your lawn is looking straggly in midsummer, resist the urge to fertilize. In fact, it’s best to stop fertilizing about 30 days before your area’s summer temperatures arrive. Applying extra fertilizer in the heat of summer can burn your lawn and create a flush of tender growth that will struggle in the hot summer weather. Never fertilize dormant lawns – wait until they green up in the fall.

High-Traffic Areas

By summer, many lawns begin to show signs of wear, especially in a few popular pathways. Consider installing stepping stones to minimize damage to your grass, and try to minimize traffic on dormant, brittle lawns. If you’re getting plenty of rainfall and your lawn is actively growing, you can apply a bit of fertilizer to these areas to help the blades recover faster.

Control Weeds

Summer is the season to get those growing weeds removed before they bloom and disperse seed for next year. Targeted postemergent herbicides are designed to kill broadleaf weeds without harming turf grass, but they must be applied when temperatures will be below 85° F for a few days. Keep in mind that during the heat of summer, ANY product can be damaging to already-stressed lawn grasses, so use sparingly or hand-pull weeds instead.

Insects and Diseases

  • Dormant or drought-stressed summer lawns can be more susceptible to insect infestations, such as chinch bugs, cutworms, armyworms, sod webworms, fire ants, fleas, and mosquitoes. Minor infestations often take care of themselves, but severe problems may require attention.
  • Summer is also the time for fungal diseases, such as powdery mildew and brown patch. Apply fungicide if needed, and avoid watering in the evening to keep nighttime moisture at a minimum.
  • Grubs will begin hatching in your lawn over the summer. If grubs typically cause problems in your lawn, you can begin applying grub control around midsummer.

 

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