Fertilizing Your Lawn in the Fall: Cool vs. Warm Season Grasses

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Is Fall a Good Time to Fertilize?

It all depends on what type of grass you have growing in your lawn.

If your lawn has warm-season grasses in it like Centipede, St. Augustine, Bermuda or Zoysia, you are at the latest possible time to fertilize your lawn. Many universities recommend that these grasses not be fertilized after the end of September since you don’t want to stimulate new, tender growth that could be damaged by frost. These warm-season grasses need to “harden off” or slowdown in growth as they begin to enter into their dormant period. If you still want to fertilize your lawn now, you could cause damage to your lawn that may not become apparent until next spring.

If your lawn has one of the cool-season grasses, like bluegrass, ryegrass, fine fescue or tall fescue, this is the best time of year to fertilize it. Fall is the time of most active root growth for these cool-season grasses. They need the food that the fertilizer provides to grow new roots. These grasses are better adapted to the cooler temperatures of fall and actually grow better at this time of year. In addition to lawn fertilization, fall is also a good time to core aerate your lawn as this process will help the roots grow better as well.

How Much Fertilizer Do I Need?

Depending on where you live, there may still be enough time to apply two applications of fertilizer this fall. You should space the applications apart by about 4 to 6 weeks. As far as the amount of fertilizer you should apply, generally speaking you should apply between three-quarters to one pound of nitrogen per 1,000 sq. ft. Determining how much fertilizer product you need to deliver requires the use of some mathematical equations.

The three numbers on a bag of fertilizer represent the percent by weight of nitrogen, phosphorus and potassium that is in the bag. So, if the bag has an analysis of 28-0-3, the bag contains 28% nitrogen, 0% phosphorus and 4% potassium. If your goal is to provide three-quarters of a pound of nitrogen per 1,000 sq. ft., then divide .75 by .28, which equals 2.68 pounds of product applied per 1,000 sq. ft. If your lawn is 10,000 sq. ft. you will need about 27 pounds of product to supply three-quarters of a pound of nitrogen per 1,000 sq. ft.
Fall is rapidly approaching, which means that leaves will be falling soon and before we know it, we will be switching from lawn mowers to snow blowers. For this, I can wait.

If you hate math, leave fertilizer application to the pros. Get in touch with your local Spring-Green today!