What Happens to Your Grass When You Fertilize

You've seen the most obvious thing that happens when you fertilize the grass: it greens up and grows. But you might not realize that when you feed the grass there's always more happening than meets the eye. The roots are growing deep into the soil to help the plant withstand heat and drought. The blades are growing and making sugars for the plants to use alongside the fertilizer you apply. Depending on the season, the lawn could be "waking up" or getting ready for winter, but either way, regular feeding is a crucial part of lawn care.

For the best looking lawn, fertilize 4 times per year— in early spring, late spring, summer, and fall. Depending on the time of the year, grass needs different things to grow. Knowing when and what to feed will make a huge difference when it comes to having a gorgeous lawn throughout the entire growing season.

What happens when you fertilize the lawn in early spring.

As temperatures rise in the spring, grass has to almost completely rebuild both its root system and top growth in a delicate balance. The new grass shoots that emerge from plants in the spring are called "tillers," and they are what give grass that fresh green look.

Too much top growth, though, and plants will be left without the strong root system they especially need for the heat of the summer. On the other hand, not enough top growth and plants can't store enough sugars to draw upon for nutrition between feedings. What's more, all of this is happening as summer weeds are starting to grow.

Northern Lawns

During winter months, cool-season grasses such as fescues and bluegrass don't go dormant (they actually remain green) but growth slows to almost a complete halt. In Northern areas, Scotts® Turf Builder® Halts Crabgrass Preventer with Lawn Food will help the lawn re-establish roots and top growth in the right balance while preventing weeds (like crabgrass) from sprouting.

Be sure to wait 4 months before seeding or sodding after using this product, and do not sprig for 5 months after applying. As with any product, follow all label directions.

Southern Lawns

Warm-season grasses such as zoysia and St. Augustine grass turn brown and go dormant during the winter. Southerners should feed the lawn in early spring with Scotts® Turf Builder® Bonus® S Southern Weed & Feed to provide food for top and root growth and kill dollarweed, purslane, and other listed weeds before they take over while grass is emerging from dormancy.

Scotts® Turf Builder® Bonus® S Southern Weed & Feed can be used on St. Augustine grass (including Floratam), centipede, zoysia, and carpet grass lawns. If you plan to seed, sod, or sprig, pay close attention to the package directions for planting restrictions.

What happens when you fertilize the lawn in late spring.

Northern Lawns

By late spring, the grass is growing quickly, and temperatures are ideal for strong root and top growth leading into summer. In the North, feed grass in the spring with Scotts® Turf Builder® Weed & Feed to give the lawn what it needs to maintain steady growth while killing weeds. Wait to apply on newly seeded, sodded, or sprigged areas until new grass has been mowed 4 times, and wait at least one month after using this product to seed, sod, or plant grass sprigs.

Southern Lawns

Warm-season grasses in Southern lawns really start to green up in the late spring, using up any reserves they might have stored from the previous fall and aggressively replacing top growth. (This is when the tillers are forming most actively in warm-season grasses). When you feed in late spring with Scotts® Turf Builder® Southern Lawn Food, the grass will continue to grow deep roots and a lush top, getting itself ready for prime time— summer.

What happens when you fertilize the lawn in summer.

Northern Lawns

Summer heat is hard on cool-season grasses. When the temperature rises above 80 degrees, for example, Kentucky bluegrass roots virtually stop growing. A summer lawn feeding helps give the grass what it needs to keep growing when temperatures drop slightly.

Summer is also a time when insects emerge and damage the surface of the lawn. Summer feedings in the North are as much about insect control as they are about grass growth. Scotts® Turf Builder® Summerguard® Lawn Food with Insect Control will give the lawn a boost when it comes out of summer dormancy and, at the same time, keep insects from taking over. 

Southern Lawns

Warm-season grasses in the South are at the peak of their growing during the warm days of summer. Many of these grasses grow by sending out runners (called rhizomes) that form dense mats that help make it hard for weeds to break through.

Feeding in the summer with Scotts® Turf Builder® Summer Lawn Food encourages this dense growth, priming the lawn to enter winter without bald or patchy spots. It also helps keep your lawn green using up to 50 percent less water* and can be used on all grass types.

What happens when you fertilize the lawn in the fall.

Northern Lawns

The fall is another time of fast growth for cool-season grasses in the North. Lower temperatures cause grass blades that might have gone dormant and turned brown over the summer to green up again while roots continue to grow deeper. During the fall, grasses are also working overtime to store sugars in their rhizomes that will help them start growing again the following year.

Scotts® Turf Builder® WinterGuard® Fall Lawn Food is a good choice for Northern lawns because it's formulated to deliver the nutrients lawns need in the fall to repair damage from the heat, drought, and activity of the summer, ensuring stronger grass in the spring.

Southern Lawns

While Northern lawns welcome fall with new growth, Southern lawns begin to grow more slowly, allowing winter weeds to begin sprouting. Scotts® Turf Builder® Bonus® S Southern Weed & Feed helps keep weeds from overrunning the lawn while giving the grass a last serving of food to store before it shuts down for the winter. It can be used on St. Augustine grass (including Floratam), centipede, zoysia and carpet grass lawns. Always read and follow directions on the package when using this and other weed-and-feed products.

As you can see, it's important to keep feeding your lawn throughout the growing season. To make it easy, visit our Scotts® Lawn Care Program page. Simply answer a few questions about your lawn, then we'll send you exactly what your particular lawn needs, right when you need it. This personalized subscription program takes the guesswork out of cultivating a gorgeous lawn, so you don't have to spend any time worrying and wondering. After all, there really is a lot happening in the lawn throughout the year—it's not just about spring!

Ready to Fertilize?

Choose the spreader that's right for your lawn size.

Small lawns: 1,500 ft2 or less

Scotts® Whirl™ Hand-Powered Spreader

Medium lawns: 5,000 ft2 or less

Scotts® Turf Builder® Edgeguard® Mini Broadcast Spreader

Large lawns: 15,000 ft2 or less

Scotts® Turf Builder® Edgeguard® DLX Broadcast Spreader

Extra-large lawns 20,000 ft2 or less

Scotts® Elite Spreader

Not sure how big your yard is? Download the Scotts® MyLawn App to measure your property and keep track of your lawn care routine.*When used as directed, greening effects last up to 6 weeks. Results will vary due to temperature and turfgrass type.