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5 Reasons Why Your Grass is Thinning Out & How to Fix it

Some thin things are good. Like those Thin Mints Girl Scout cookies. 

But nobody ever looks out at their lawn and says, “Man, I wish my grass was thinner.”

If you’re munching a cookie and muttering, “Why is my grass thinning out?” we have some good theories. 

Here are 5 potential reasons why your lawn is thinning.

1. Your Lawn is Hungry

When you’re feeling too thin, you eat, right? (Let’s just assume somebody somewhere is feeling too thin.) 

Same with your lawn. It needs nutrients to grow thick and thrive. When you ask, “Why is my grass thinning out?” your lawn is out there shouting, “Hey! I’m starving!”

lawn care technician fertilizes grass
How to fix thin grass? Feed it with proper fertilization. 

Maybe you’ve been neglecting your lawn’s fertilizer needs, only applying it once or twice a year, or forgetting completely. It happens. Life gets busy, right?

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Here’s a reminder. When to fertilize your lawn to help prevent thinning grass?

  • Mid-to late-April, once the soil temperature reaches 55 degrees.
  • Three times during the summer growing season: mid-May, around the end of June, and in early to mid-August.
  • Fall. This final fertilizer treatment in fall includes important slow-release granular fertilizer that feeds your hungry lawn for the winter and helps it revive in the spring.

And please, choose quality fertilizer. Buy it at a local garden center or fertilizer supplier rather than a big box store. Or even better, hire a lawn care service with superior products. (Hint: that’s us.)

2. Your Lawn Can’t Breathe

Compacted soil is a big problem here in Idaho and can cause thinning grass. 

Kids, pets, and just general activity can compact your soil over time.

When your soil becomes compacted, your lawn is gasping for air. Its roots can't take in water or nutrients, which weakens your turf. Suddenly, your grass is thinning out. 

lawn care expert aerates grass

How to fix thin grass? Say hello to aeration and seeding. 

Lawn aeration uses a machine to pull out plugs of soil, creating spaces so that air and water can penetrate, which leads to healthier roots. Healthier roots lead to a thicker, healthier lawn. 

Lawn aeration also helps break down thatch, that layer of dead grass and stems that sits between the grass blades and the soil.

Aeration is great, but you’re not done yet. It’s typically followed by overseeding, as the holes created by aeration are perfect new homes for the grass seed. 

A proper seeding with quality grass seed can often do the trick to fill in thinning grass.

3. Thinning Grass? Might Be Too Much Shade

Maybe your grass was nice and thick years ago. What happened?

Your trees grew. (Trees are shifty that way.)

As trees mature, they cast more shade on your lawn. Nice for picnics. But your grass craves sun. 

Grass seed in lawn

Even shade-tolerant grasses need at least 3 to 4 hours of direct sun, or 4 to 6 hours of dappled sunlight, each day. 

How to fix thin grass due to shade? You have a couple options:

  • Prune or thin the trees and tall shrubs that shade your thinning grass.  As you snip, thin the canopy so that sunlight can make its way to the grass beneath. Removing lower tree branches can help, too, so sunlight can sneak in on a slant to reach the grass.
  • Use the right grass seed. Here in Idaho we primarily use a blend of Kentucky bluegrass and perennial ryegrass. This blend can tolerate some shade and works in most situations to help thinning grass fill in.

4. Gobbling Grubs

Thinning grass? Maybe grubs are out there getting fat. 

Grubs are the larvae of Japanese beetles, June beetles, chafers, and other beetles. And they’re super hungry. 

They feed on grass roots and organic matter in the soil, causing sections of grass in the lawn to thin or even die.


How to tell if your grass is thinning out because grubs are chowing down? Grab a handful of your lawn and tug. If it rolls up like loose carpet, you probably have grubs. They eat the roots holding the turf firmly in place on the soil.

Get rid of grubs to help your thinning grass. The trick is to kill grubs before they hatch and start to feast, so we’ll apply preventive lawn grub control in the spring to give them the boot.

How to fix thin grass?  A well-fed and maintained lawn will have fewer grubs than one that’s hungry and stressed. Keep up with that fertilizer.

5. Grass is Thinning Out? Fix Bad Soil

You can’t see the soil, so it’s easy to forget about its needs. It matters. Poor soil can cause thinning grass.

How to fix thin grass? Add organic matter — plant debris, shredded leaves, animal manure, grass clippings. It just looks like slimy gunk to you, but soil craves it. Organic matter adds great lawn nutrition to depleted soils and brings in helpful microbes and earthworms. 

What’s so great about worms? They do their worm thing and break down the organic matter, tunneling and creating pockets that lighten the soil and allow air and water to reach the roots.

Top dressing helps, too. Use a lightweight amendment like compost or peat moss and apply it over the top of your thinning lawn. 

Finally, mulch your grass clippings for a lawn nutrition boost. It’s easy — just use a mulching blade on your lawn mower. As the grass clippings decompose, they create a layer of compost on top of the soil. You can also mow over leaves in the fall instead of raking them, as this also adds organic matter into the soil. (That’s right — we just gave you permission to skip the raking. You’re welcome.)

Is Your Lawn Ready for a New Best Friend?

There are a lot of forces at work out there causing your thinning lawn. It’s a lot to keep up with, right? 

You have to stay on top of a fertilizer schedule, battle gobbling grubs, enrich your soil, aerate and seed, thin your tree canopy. That barely leaves any time to munch Girl Scout cookies. 

How to fix thin grass? Leave it to us. 

Choose an Idaho Falls or Boise professional lawn care service that bundles your yard’s most-needed treatments into one convenient, no-fuss, six-visit plan that includes everything your lawn needs to grow healthy and green, including weed control and grub control that’s perfectly timed throughout the year.

Fertilizing, weed control, grub control. Done.

Got a few minutes? That’s all you need to get started.

Fill out the form on this page.
Call us at (208) 656-9131.
Or read more about our services.

Then kick back and relax in your healthy, thriving yard.

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