The Basics of Lawn Fertilization

When to fertilize your lawn

Timing is key to successful lawn fertilization.  You should apply fertilizer during the growing season, as fertilizing a dormant lawn can promote weed growth.  If you have cool-season grass, such as bluegrass, ryegrass or fescue, fall is an ideal time to fertilize your lawn.  The nutrient boost will help your grass recover from the summer, prepare it for the winter and come back earlier and stronger in the spring.


Another important aspect of timing your lawn fertilization is ensuring you leave enough time between treatments.  Different types of fertilizers release nutrients over different periods of time.  Fertilizing a lawn before a previous application is complete can lead to over-fertilization, which can burn your grass.


Types of fertilizers

Understanding fertilizer ingredients and how they work will help you choose the right mixture for your lawn.  Most fertilizers contain three main elements: nitrogen, phosphorous and potassium.  Nitrogen plays the biggest role in your grass's growth and green color and is the most important element to apply during your fall lawn fertilization.  Phosphorous helps establish and strengthen root systems, while potassium makes lawns more resistant to a variety of stresses, including drought, cold, disease and traffic.  Blends high in phosphorous and potassium are often used for fertilizing a new lawn or renovating an old one.


Different types of fertilizers contain different combinations of these elements.  Fertilizers are labeled in a standard way - with three numbers separated by hyphens - to show how much of each ingredient they contain.  The first, second and third numbers represent the amounts of nitrogen, phosphorous and potassium, respectively.  A 100-pound bag of fertilizer labeled 24-4-12 contains 24 pounds of nitrogen, 4 pounds of phosphorous and 12 pounds of potassium.  The other 50 pounds are filler ingredients.  For fall lawn fertilization, a nitrogen-heavy, slow-release blend is usually recommended.  Slow-releasing fertilizers require fewer applications and minimize the risk of lawn burn.

How to fertilize your lawn

Before you fertilize, be sure your lawn doesn't have excessive thatch buildup.  Thatch can block fertilizer from reaching your lawn and can cause it to burn your grass. Fertilizing a lawn during a drought can also cause grass burn, so be sure conditions are not too dry.


Using a spreader is the easiest way to apply fertilizer to your lawn.  Avoid filling the spreader while it's on your lawn, as this can cause the fertilizer to spill out and burn your grass.  Also, be sure you calibrate your spreader so it releases the recommended amount of fertilizer.


After fertilizing a lawn

After you fertilize your lawn, water it immediately.  Then, it's safe to mow.  Just be sure that the lawn isn't wet when you cut it, as this can damage the roots of your grass.  You should continue to cut your grass as long as it's growing.  Using sharp mower blades will help you get the crisp look you want and also make your lawn less susceptible to pests and diseases.  To further protect your lawn from damage, avoid taking more than one-third off the length of your grass each time you cut.


For winter, you should trim it down to a height of approximately 2 inches.  This will help prevent the grass from getting matted beneath the snow, which can lead to snow mold.  Get the mower blades and other quality lawn mower parts you need to prepare your lawn for winter from MTD.


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