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When to fertilize a lawn

when to fertilize a lawn lush green grass

A wide, sweeping swath of lush green grass is the dream of many a homeowner.

When to fertilize a lawn

By Mary Van Doren on May 22, 2018

Whatever you think you know about when to fertilize a lawn, it’s probably wrong

Americans love their generous swaths of green – so much so that more than 75% of all households participate in some form of landscape maintenance, according to the National Gardening Association.

But when it comes to understanding how to perform that landscape maintenance, it’s a good bet that almost all of us get our information from TV commercials and instructions on bags of fertilizer that we buy at the big box stores. 

And that’s why those who think they know when to fertilize their lawn are often … completely wrong.

Lawn product companies are in business to make money, so it’s in their interest to convince you to fertilize your personal patch of paradise practically year-round. They make it temptingly easy, marketing products that are numbered and geared toward application on certain dates. No thinking required on the part of the homeowner!

But the truth is, most lawns only need to be fertilized twice a year. They need less fertilizer than the box store wants to sell you, and they all need different types of fertilizer. Finally, they need fertilizer exactly when you’ve stopped thinking about it altogether. 

When to fertilize a lawn: not in the spring

You always know it’s spring when dozens of lawn product commercials pop up like mushrooms after a spring rain. Those luscious green expanses in their commercials – certainly not digitally enhanced! – are almost impossible to resist.

But the truth is, it’s not the advent of the traditional growing season that dictates when to fertilize a lawn. It’s the natural growth cycle of the grass – and applying fertilizer at the wrong time can damage the plant instead of strengthening it.

As it turns out, in all cold-weather parts of the country, grasses need their nourishment most in the fall, just when most of us are putting away the yard tools and oiling up the snowblower.

According to TheFamilyHandyman.com, the most important fertilizer date is just as the kids are going back to school. “If you fertilize just once a year, apply it around Labor Day. That’s when your lawn is the hungriest and when it will respond best to the nutrients it receives.

“Fertilizing at this time will help replenish food reserves after a long, stressful year of growing and before the harshness of winter sets in.”

Springtime, when we’re all urged to rush to the store to buy a truckload of fertilizer, is actually when the grass’s natural growth cycle is already urging it to get moving. Fertilizing in spring is generally overkill: It urges the grass to grow so fast that we wind up mowing more often. 

In fact, the only reason to fertilize your lawn in the spring is to give it a little help just as the nutrients applied in the fall are being used up. Using this schedule, you’d be applying fertilizer in late spring, not just as the temperatures start to rise in April, when many of us jump to it.

And if you’re doing it right, after you apply that primary dose around Labor Day, you should also giving your lawn a secondary treatment in mid-October to prepare it for winter. This application nourishes the lawn for winter hibernation and gives it that that very early spring sustenance.

Rotary fertilizer spreader

A rotary spreader is a good option for fertilizing a lawn.

According to some lawn experts, you can actually get away with just those two autumn applications! And that’s certainly good news for most of us who have enough to do around the homestead already.

All of this means you only have to fertilize lightly in spring, as mentioned above, if you can’t help yourself, or your lawn is still making a long comeback from neglect. If you’re really into walking behind your spreader, you can apply more fertilizer in mid-summer, but keep in mind that fertilizing during hot weather, unless you use an organic product, can be harmful to your lawn.

It’s important to note that this schedule differs for those who have warm-weather grass in the southern parts of the U.S. In that case, the natural growth cycle calls for fertilizing in late spring or early summer, because that’s when it kicks into high gear. You can then put down a second application in late summer, but don’t fertilize after Sept. 1.

How to find out what your lawn wants, and how much to give it

There’s more to lawn care than understanding when to fertilize a lawn. For one thing, most professionals agree that Americans largely over-fertilize routinely, guided by those instructions from companies that want to sell lots of fertilizer.

But as TheFamilyHandyman.com notes, too much fertilizer, especially in sandy soils, will not only leach into groundwater, but will spur too much of a good thing causes grass to grow weak, become more susceptible to disease, and create so much thatch that it will choke itself.

Many experts advise, then, that you can get away with using half the amount of fertilizer that the manufacturer recommends. 

And perhaps even more important than when to apply fertilizer and how much, is something else quite basic. Your lawn depends as much on the soil it grows in as it does on the chemicals you give it to thrive, so your ultimate goal should be to figure out what the soil is and isn’t delivering before you choose fertilizer and start filling the spreader.

And finally, what you put down is also dictated by the kind of grass you have. Not only are lawns different in north and south, but also in different regions, or even by different choices made by different neighbors for original seeding.

Some grasses do better in the northwest’s cool but humid climate, and others in the west’s warm but arid climate, but there are many grasses that thrive in each climate, and they have different nutritional requirements. 

For instance, zoysia grass has become quite popular in recent years, especially in transition climates, because it’s a warm season grass with greater cold resistance than other grasses. It can grow next door to a lawn filled with the common Bermuda grass. But the two fertilizer needs are different.

zoysia grass

Zoysia grass, a popular, sturdy broad-leaf grass, has specific nutritional needs that are
 from those of other popular grasses.

According to 49erLBSU, a lawncare Expert on JustAnswer, “Zoysia grass does best with less rather than more fertilizer. It will then form a layer of thatch under the green grass if too much fertilizer and water are used. Use fertilizer in spring when the zoysia grass is at least half green and repeat later in midsummer. Recommended is any brand of turf fertilizer that contains slow release nitrogen.”

At the same time, for Bermuda grass, he notes, you should apply straight nitrogen. But wait! Expert Daniel Stover, a golf course superintendent, warns that when you’re preparing Bermuda grass for dormancy in the fall, the best thing is to “apply a source of potassium at the rate of 1/2lbK/1000 sq ft.

“This will give it some much needed energy reserves to hold it through the winter. Secondly I would not apply any nitrogen sources anytime after October. Your Bermuda at this time is in the hardening off stage and looking to slow its growth down. Applying nitrogen would only screw up the natural process.”

The home landscaper’s best friend: The extension service

So in addition to understanding when to fertilize, it’s important to understand the needs of your particular lawn – including the soil it grows in. That’s why homeowners with problem lawns are routinely urged to get a soil test to find out what the heck is down there under the grass.

In particular, they advise that you get your soil professionally tested by taking samples yourself and having the right scientists run test, rather than using a home test. Randomly pull 10 to 12 individual soil samples from your lawn to a depth of 3 to 4 inches, removing any vegetation from the sample. Mix these together and send off about a cup of soil to be tested.

Where to send it? If you’ve done any research on the Internet about your lawn, you’ve probably seen suggestions to contact your county or state extension service. This is the best advice you can possible get: These folks are there to help you with all kinds of landscape questions. 

They can test your soil, help identify the grass if necessary, the advise you on timing, type and amount of fertilizer you should be using – much more accurately than can the instructions on the bag of fertilizer in the box store.

And it’s easier than you think to find them: Since you’re on the Internet right now, go to your favorite search engine and search for “[county] extension service” or “[state] extension service." Search for a service in Connecticut, for example, and the top result takes you to the University of Connecticut’s Extension Service, complete with information on local offices, programs for homeowners and more.

So once you understand that the box store’s advertising isn’t your best resource, you can easily turn to the people who are. Of course, knowing that when to fertilize a lawn is just one of many questions you’ll want answered may make you feel a bit stressed, but in the end, that lush, green lawn will probably make you believe it’s all been worth it. 

When do you fertilize your lawn? Do you do it because of advertising or because of professional advice? Please share your thoughts with us in the comments below!