Cool season turfgrass management

Has your turf taken a beating over the past year? If improving your cool season turf is on your to-do list, September could be a very busy month.

If you were to choose one time of year to fertilize a cool season lawn, September would be that month. As days shorten and night time temperatures moderate a little, cool-season grasses begin the tillering process. This is the process through which new shoots start to form at the base of existing plants, naturally thickening up the stand. Fertilization is important to help ‘promote’ this tillering process.

Your nitrogen rate doesn’t have to be high. One to one and a half pounds of actual nitrogen per thousand square feet in the form of a quick release fertilizer will likely do the trick.

Use a fertilizer that contains phosphorous (P) and potassium (K) as recommended by a soil test or apply a balanced fertilizer product so some level of P and K are being applied.

If you want to put the effort in to a second fertilization, mark your calendar for November. A November fertilizer application will help the grass green up earlier next spring and provide the nutrients needed until summer. It, too, should be quick-release fertilizer applied at the rate of one pound of actual nitrogen per 1,000 square feet

If the past summer’s drought and heat thinned out your turf grass stand, September is a good time for overseeding. Start by evaluating your thatch layer and adjusting mowing height. Thatch layers greater than a quarter inch can cause seeding issues and should be addressed before overseeding.

This is also one of the only times we would typically advocate for reduced mowing heights. Drop the mowing height to an inch and a half and remove the clippings during the mowing prior to overseeding. Overseeding can be done as simply as using a rake to roughen the soil surface and then applying seed, but is typically the most successful when combined with core aeration or a verticutting operation. Verticut seeding is the best, since it typically results in the best seed to soil contact – an integral part of the chances of success with overseeding.

One more September turf chore that you might consider is core-aeration. Core-aeration should be done when soil is just moist enough so it crumbles easily when worked between the fingers. Use of a hollow tine aerator is preferred so cores can be removed and deposited on the soil surface to break down.

Run the aerator to a depth of two to three inches and repeat aeration passes (from different directions) so the resulting holes are spaced two to three inches apart.

When done correctly, core-aeration helps reduce compaction while encouraging a more rapid decomposition of thatch. It can also help increase water, nutrient and oxygen movement in the soil, while providing an environment conducive to overseeding and lime applications.

For more specific information on any of these practices, contact a Meadowlark Extension District Office or e-mail me at

We have publications on lawn fertilization, overseeding, aeration and much more that can help with your turf improvement projects.

David Hallauer43 Posts

David Hallauer is the Meadowlark Extension District agent in the areas of horticulture and crops and soils.


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