Fall Fertilizing for a Healthy Lawn

Why fertilize in the fall? Read on to find out, and learn how to do it right.

What your grass needs to grow
There are 16 different elements your lawn (or any other plant, for that matter) needs to grow. Some are plentiful (carbon, hydrogen and oxygen) from the air and water. Others are found in the soil, and some will need to be fed to your lawn with fertilizer.


Have your soil tested before you fretilize your lawn. A soil test will tell you the levels of pH, phosphorous, potassium and organic matter in your soil, as well as the percentage of sand, silt and clay.

Luckily, many of the elements are needed in trace amounts, so you don't have to be concerned with providing every last one of them. These elements (excluding the abundant oxygen, hydrogen and carbon) are broken up into three categories in order of importance: macronutrients, secondary nutrients and micronutrients.

The macronutrients: nitrogen, phosphorus, and potassium, are the most important because your lawn uses them in the greatest quantities. Those big numbers on all the fertilizer bags, such as 15-5-10, represent the ratio of nitrogen, phosphorus and potassium by weight (see “The Big Three,” below).

The secondary nutrients: calcium, magnesium, and sulfur, can usually be found in sufficient quantities in the soil. If your lawn's pH is out of whack, lime will supply calcium and magnesium to raise pH, while sulfur lowers it.

Micronutrients: iron, zinc, manganese, copper, molybdenum, boron and chlorine, are also usually available from the soil. Without a soil test, you may never know if your lawn is deficient in any of these elements, with the exception of iron. An iron deficiency will turn your grass yellow.

Your local agricultural extension or a nearby university can usually perform a professional soil test for a modest fee. Private labs provide the same service, but with a higher price tag. Look for private labs in your local phone book under “Soil – Analysis,” “Soil – Testing” or “Laboratories – Testing.” The home soil-test kits available at garden centers and nurseries tell you only the pH of your soil, so laying out a few bucks for professional test is really your best bet.


Don't have a "more is better" attitude when it comes to fertilizer. Feeding more nutrients than your lawn needs can harm it.

When to feed
The best time of day to fertilize is when the grass is dry. Fertilize the lawn; then water it to knock the fertilizer off the blades of grass and put it into the soil. Don't fertilize on wet grass, as the grass dries, the fertilizer left on the blades can actually burn the grass in the hot sun.

Next comes the tricky part, what times of year you should fertilize. Fertilization times depend on what type of grass you're growing. You can follow one general rule of thumb: Fertilize before your grass enters its period of active growth. For cool-season grasses, this is usually in the spring and fall. Warm-season grasses will benefit from a feeding in the late spring through the summer.

How often should you fertilize? This is where your preference comes in. You'll probably have to fertilize your lawn at least once a season to keep it alive, but it's up to you to decide how much growth you really want. Low-maintenance lawns need to be fertilized only once or twice a year, while high-maintenance ones will need feeding once a month during the active growing season. Either way, you’ll have a healthy lawn. The low-maintenance lawn just won’t be as lush and green as a high-maintenance one.

Get to know your grass – what type of nutrients it needs, how much it needs and when it needs water. With a little time and care, your lawn will be able to withstand pretty much anything Mother Nature can throw at it.

The Big Three
Use your soil test results to know how much of what is needed.

  • Nitrogen (N), the most important element that your lawn needs, aids in rapid shoot growth and keeps your lawn a healthy, rich green. If your lawn is nitrogen deficient, it will turn yellow and wither. Since nitrogen leaches through the soil easily, water runoff containing this surplus nitrogen can end up polluting the groundwater or nearby lakes and streams.
  • Phosphorus (P) is essential for root and shoot growth. It is usually present in sufficient quantities in the soil especially if you added it to the soil before planting. In fertilizers, it is in the form of phosphate (P2O5). To prevent excess algea growth in lakes and streams, some municipalities that have high levels of phosphorus in the soil require use of phosphorus-free fertilizers on established lawns.
  • Potassium (K), supplied by potash (K2O), is necessary to keep your lawn resistant to weeds and disease and to promote overall health. It is the all-in-all lawn-health booster and helps your lawn better withstand heat and cold, drought and wear.

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