The fall season is just around the corner. With it brings cooler temperatures and likely a little less yard work. But, before you put away all of your gardening tools, consider fertilizing your cool-season grasses.

Cool-season grasses such as tall fescue may lose roots during Oklahoma’s sweltering summers. However, the fall and spring seasons are crucial for root growth. Proper fertilization can benefit turfgrass if applied according to certain recommended procedures. A lawn with a healthy root system will be better equipped to survive moisture and temperature extremes than those with poor root systems.

Warm season grasses, such as bermudagrass or zoysiagrass, shouldn’t be fertilized after early September. Late, heavy applications of fertilizers containing nitrogen actually can be detrimental to bermudagrass and zoysiagrass health by encouraging lush shoot growth. This can result in severe disease and/or winter injury. 

Cool-season lawns such as tall fescue can benefit from a mid- to late-September fertilization with nitrogen at a rate of 1 pound of actual nitrogen per 1,000 square feet.  The following are a few tips to remember when fertilizing your lawn.

Always be sure to conduct a lawn soil test before applying fertilizers to your yard.  You can refer to the soil testing collection procedures and fertilizer schedule as outlined in OSU Extension Fact Sheet HLA-6420. All OSU Cooperative Extension fact sheets can be found at

When spreading fertilizer, use properly calibrated spreading equipment. The label on the fertilizer bag has information for the proper setting on your fertilizer spreader.

Use fertilizers with a mixture of quick-release and slow-release nitrogen sources. Examples of quick-release nitrogen, also known as water-soluble, include urea, ammonium nitrate, ammonium sulfate, diammonium phosphate, and potassium nitrate. Examples of slow-release (also called water-insoluble) nitrogen sources include methylene ureas, IBDU, urea formaldehyde, sulfur-coated urea (SCU) and polymer coated urea (PCU).

Don’t apply fertilizer to impervious surfaces such as sidewalks and driveways. If this happens, simply use a broom or blower to remove it from the surface. This is important because fertilizers left on hard surfaces can become an environmental concern when it rains and they run off into drains or ditches.

Once the fertilizer is applied, lightly water it in. Don’t apply fertilizer to your lawn right before heavy rainfall or deep irrigation.

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