Everyone knows that fertilizing is a big part of "winterizing" your lawn, but there are some other steps, too that you should take to prepare your grass for winter. But before we discuss fertilizing and the rest, it is helpful to understand why we bother winterizing lawns. Indeed, some of you may be wondering what the point of it is, since the grass doesn't even grow in winter.
First of all, not all grass is created equal. Before you even consider taking steps to winterize your lawn, determine what type of grass you have: cool-season or warm-season.
Warm-season grasses grow actively from mid-April to mid-October: They like the warm-to-hot weather. Cool-season grasses, by contrast, grow the most in late spring and early fall: They like cool-to-moderate temperatures. But what about the other times of the year? This brings up the issue of dormancy.
What Does Dormancy Mean?
Plant dormancy literally refers to a state during which a perennial plant is sleeping (from the Latin, dormire, "to sleep"). It is a defense mechanism plants have to help them through hard times, such as periods of cold, heat, or drought. It is a temporary state of metabolic inactivity or minimal activity. The plant may look dead, but it's really just sleeping.
Warm-season grasses go totally dormant in winter (to help them survive the cold) in all but the warmest areas of the U.S., such as South Florida: They're hitting the pause button and just waiting for winter to be over, after which time they'll pick up where they had left off.
Cool-season grasses go dormant in summer (to help them survive the heat). Cool-season grasses also experience a period of semi-dormancy in winter (because they like it cool, not frigid). However, activity can remain vibrant at the root level for them throughout winter: They are building reserves for their big growth spurt in spring.
When (and If) You Should Apply a Winterizing Fertilizer
Keep these distinctions in mind when you plan your winterizing strategy. Winterizing is most important for cool-season grasses. So what should you do for a warm-season grass? In an area such as northern Florida, a warm-season grass will go dormant in winter; in which case, stop fertilizing after September 1. Fertilizing after this time would only promote new growth that will die in the cold to come, a process that stresses out your lawn. In southern Florida, where the grass doesn't go dormant in winter, simply continue with your normal fertilizing regimen.
For these reasons, the focus of this article is on winterizing cool-season grasses in the northern part of the United States. In the far north parts of the country, apply a winterizing fertilizer in October. In the rest of North, you can wait till November if you choose. In fact, fall is the most important time to fertilize a cool-season grass. Other than the fertilizer, all you need for the job is a spreader.
Why Is Applying Winterizing Fertilizer So Important?
The shortened days and cooler temperatures in fall tell your cool-season grass it's time to get ready for winter. It's time to put less energy into growing grass blades and more into building food reserves at the root level. Those food reserves will be used in spring to help your grass wake up, grow vigorously, and enjoy its most productive time of the year. Your job is to aid that building of food reserves: That's what the fertilizing part of "winterizing" is mainly about.
ortunately, the fertilizer companies make that job easy, providing a fertilizer product specifically called "winterizer." It will contain two main ingredients: nitrogen and potassium. The ratio is usually 2 parts nitrogen to one part potassium. Follow the instructions on the package carefully: Using too much fertilizer can burn your grass.
Here are the other steps to take in a thorough program to winterize your lawn:
Mow to the Proper Height
Aim for a grass height of 2 1/2 inches, and, each time you mow, remove just the top 1/3 of the grass blade. The easiest way to stick to these recommendations is to mow your lawn when it stands about 3 2/3 inches high.
Achieving a balance is important because either extreme is bad. Cutting too short stresses the grass and gives more sunlight to weeds. The weeds will reproduce, causing you headaches next spring. But allowing grass to grow unchecked leads to matting when fall rains come, which invites molds and other diseases. It also offers winter shelter to pests.
Keep Your Lawn Weeded and Water
Speaking of weeds, fall is no time to let up on weed control. Pay particular attention to perennial weeds; for example, dandelion (Taraxacum officinale). Also focus on weeds that go to seed (so they don't reseed themselves) in fall; for example, common ragweed (Ambrosia artemisiifolia).
And it may sound odd, but winter presents a lawn with desert-like conditions in the northern part of the United States. Sure, there may be plenty of snow. But even on days that the snow melts, the ground is frozen so deep that no moisture can get down to the roots of the grass. Making sure that your grass is adequately watered in fall, before the ground freezes, will help get it through winter's drought.
Remove Fallen Leaves
Don't let fallen leaves stay on your lawn too long. They can harbor diseases and deprive your grass blades of the light they need. If you don't like raking, run your mower (with the bag attached) over them.
Once you have the leaves removed, again, you can bag them and have your town pick them up (if that's the policy where you live), compost them, or use them as mulch.
Compost and mulch are different. Organic matter becomes "compost" after it has decomposed completely. Once decomposed, it can release nutrients into the soil. By contrast, when leaves or other organic matter are intended for mulch, they should not be decomposed completely.
Dethatch Your Lawn
Thatch is made up of organic matter in your lawn that is slow to decompose. If the layer of thatch in your lawn is too thick, it negatively impacts grass health. When you dig the tines of a rake into the lawn in the process of raking, you are also controlling thatch at that same time. This is why raking may be a superior method of leaf removal as compared to other methods.
Overseed Your Lawn
When the grass in your lawn grows thickly, the benefits go beyond mere appearance. In a thick lawn, the weeds are crowded out. Not only is there little space for them to grow, but the grass also outcompetes them for resources (water, nutrients, sunshine). Overseeding in fall is a great step to take to ensure a better (and lower-maintenance) lawn in spring.
Broadcast the seed with a spreader, using the settings recommended on the bag of grass seed. Keep the lawn watered afterward unless rain is in the forecast.
Add Lime If Needed
Don't add garden lime automatically: You may not need it, and, yes, there is such a thing as too much lime (lawns usually like a neutral soil pH). So run a pH test first. If the test shows your soil is too acidic, then add lime using a spreader. Your county extension can help both with the test and with the setting needed on your spreader to distribute the lime correctly (based on the test results).
Fertilizing Lawns. University of Minnesota Extension