The Fall Lawn


by Karen Weiland, Advanced Master Gardener



A deep green, lush lawn is nice to look at but unfortunately does require some care to become that way.  Applying fertilizer is one of the most important procedures done as it influences grass color, helps it deal with stress and prevents weed invasion and disease.

Nitrogen (N), Phosphorus (P) and Potassium (K) are the three major nutrients needed by grass.  Nitrogen gives the grass its deep, rich color and promotes vigorous growth.  Potassium builds strong roots and Phosphorus is important in stimulating early root growth and promoting plant vigor.

Two important factors to consider when applying a fertilizer are when and how much.  Our cool season grasses will benefit most when you apply the majority of N fertilizer from late summer through autumn. Consider Labor Day and Halloween as times to apply fertilizer during your fall schedule.  This will help the turf grass overcome any summer stress it may have experienced, it enhances the thickness, maximizes its green color and prepares the turf for winter.


There are two types of Nitrogen, quick release or soluble and immediately available to the plants and slow release or insoluble and will release the nitrogen slowly.  A good turf fertilizer contains some of both.  The slow release will provide nitrogen over a period of time but is not available to the plant during cool weather.  The fast release will provide nitrogen almost immediately after it is applied and during cool weather.  To thicken your grass during late summer and early fall (late August thru early November), you should apply up to 1 pound of nitrogen per 1000 square feet each month, spread it evenly, apply when foliage is dry and then water it in after application.  If you apply N fertilizer in the spring it is best to use a slow release one to minimize excess growth, otherwise you may be mowing every other day to keep up with it.

It is recommended to obtain a soil test before applying a lawn fertilizer so you can determine what mineral elements your soil needs.  Soil test results will also tell you the soils pH, which is the acidity or alkalinity of the soil.  If the pH is too high or too low, it will limit nutrient availability and turf growth, and can reduce turf health.  Poor soil pH should be corrected to have healthy turf.  You can learn more about soil testing for lawns by looking at publication AY-18-W on the Purdue Extension website.  While you are there you may also like to pull up  publication AY-22-W which explains in detail how to fertilize cool-season lawns.

Using a broadcast or rotary spreader ensures that granular fertilizers are applied at the proper rate and are best used for large, open areas.

I usually return my grass clippings to my lawn.  It’s free fertilizer.  Grass clippings contain valuable nutrients that can generate up to 25 percent of your lawns total fertilizer needs.  In years past it was recommended to set the mower blade down and cut the grass short for the final mowing in the fall.  This is no longer recommended.  Photosynthesis is high during the fall even with the cooler temperatures.  The higher the photosynthesis, the more energy the plant will store over the winter and into spring thus producing a healthier grass plant.  Mowing off more of the grass blade will result in reduced photosynthetic capacity which will reduce energy storage and a decreased plant performance the next summer.

Keep these tips in mind when fertilizing your lawn.  Apply fertilizers to actively growing grass.  Do not apply to dormant or severely drought-stressed grass.  Use a rotary spreader if possible. They may be less time-consuming and provide more uniform coverage than the drop type spreaders.  Use a broom or blower to return any fertilizer particles to the turf that land on sidewalks, driveways, etc.

As always, Happy Gardening!

More information about gardening and related subjects is available online here.  The Purdue University Cooperative Extension Service can be reached at 499-6334 in LaGrange County and 636-2111 in Noble Co., 925-2562 in DeKalb Co. and 668-1000 in Steuben Co.