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9 Reasons Your Lawn is Yellow and How to Fix it

Is your lawn looking yellow in spots—even though you water diligently? It could be yellow for a number of reasons:

  1. Lawn grubs
  2. Lawn fungi
  3. Watering issues
  4. Compact soil
  5. Animal urine
  6. Nitrogen fertilizer overload
  7. Nutrient deficiency
  8. Mowing problems
  9. Dry weather

1. Lawn Grubs

Cranberry Girdler Larvae

Your yellow lawn culprit could be a type of lawn grub! Any pest that eats at the roots of your lawn will cause the lawn to yellow:

  • Billbugs appear in June–July and eat from the stem of grass blades into the roots, causing large brown/yellow areas of grass amongst small patches of green grass.
  • White grubs eat the roots of the grass, causing irregularly shaped brown patches on the lawn in the late summer and early fall.
  • Cranberry girdler creates large yellow patches of grass with darker dead patches in late summer and early fall.

If large sections of your grass can be pulled up easily, you likely have a grub problem. The good news is that most pests can be controlled by applying insecticides to your lawn.

2. Lawn Fungi

Necrotic Ring
Necrotic Ring

Did you check for grubs and see nothing under the grass? Maybe it’s a fungus—not a grub—that is killing your lawn.

Ascochyta causes splotchy yellow areas on your grass that appear when hot weather directly follows a cool rainstorm. Ascochyta usually only affects the top part of the lawn. To treat it, aerate the lawn. To prevent spreading, mow less when the disease is present.

Necrotic Ring causes rings of yellow grass to appear in your lawn. This fungus can be spread through dirty aerators and usually lasts for about 3 years before dissipating. Necrotic ring can often be managed through fertilizing and overseeding affected parts of the lawn.

3. Watering Issues

If a fungus isn’t the problem, maybe watering is. Simply watering correctly can improve your lawn immensely. Lawns that are watered daily have shallow root systems, which creates weaker grass that yellows quickly under stress. To avoid overwatering your lawn, water less frequently for longer periods of time.

Underwatering can also cause problems in the lawn. Checking for dried-out lawn is easy: pull up on the grass. If grass blades come up, then the grass needs more water.

Be sure to follow professional watering recommendations so your lawn gets just enough water—but not too much!

4. Compact Soil

Perhaps watering is not the only issue. Your grass may also look yellow if the soil underneath is too compact—this makes it difficult for grassroots to penetrate deep into the soil, weakening the grass. You can determine if your soil is too compacted by doing the following:

  • Take a sample of the soil—gray, hard soil is too compacted
  • Observe your lawn. If water runs off high parts of your lawn quickly and pools in lower parts of the lawn, it’s too compacted.

Compact soil is often caused by overwatering and excessive foot traffic. It can also easily occur in lawns that have a very thick thatch layer. Thatch that is over 1-inch thick should be dethatched to keep the grass healthy. To help remedy compacted soil and dethatch your lawn, aerate it.

5. Animal Urine

Have you ruled out all the other options? Maybe the neighbor dog is the yellow lawn culprit.

Many animals have a highly concentrated nitrogen content in their urine that can burn your lawn when focused in one area. To prevent your lawn from burning, try either training your pet to go elsewhere or spraying down affected areas immediately to help dilute the urine.

If your lawn already has damage from animal urine, try overseeding those areas:

  • Remove any matted, dead grass from the area
  • Use a small gardening tool to poke a few shallow holes in the soil
  • Sprinkle a generous amount of grass seed over the whole area

6. Nitrogen Fertilizer Overload

If your whole lawn looks yellow, it could be a fertilizer burn. The grass turns yellow because the excess fertilizer burns the grass blades.

Fertilizer burn
Fertilizer burn

Make sure you follow product recommendations when fertilizing your lawn to avoid burning it. If you think you have added too much liquid fertilizer to your lawn, try to dilute it by immediately watering the area.

If your lawn was burned because it was over-fertilized, try the following:

  • Check the grassroots to determine the amount of damage
  • If roots are still alive, water the area very well—with luck, the grass may revive itself
  • If the area is still yellow a couple of weeks after heavy watering, rake the area
  • After raking and tilling the area, overseed and water well to regrow the lawn

7. Nutrient Deficiency

Conversely, your grass can also turn yellow if it isn’t getting enough nutrients. Look for these signs to determine if your lawn is yellow because it’s not getting enough nutrients:

  • Grass blades turn yellow or brown at the tips
  • Grass grows very slowly and thinly
  • Grass wilts very easily
  • Grass is a light green color instead of a deep green

Be sure to fertilize your lawn so it can benefit from added nutrients—just make sure you don’t fertilize more than once every two weeks.

8. Mowing Problems 

Your lawnmower could be the reason your lawn is yellow. Mowing grass too short in hot weather can cause it to burn because shorter grass will naturally have a shorter, weaker root system.

If the mower blades are too blunt, your lawnmower will tear grass blades rather than cutting them cleanly. This can cause the top parts of your grass to look yellow and dry.

To prevent damage from mowing-related problems, do the following:

  • Sharpen the blades of your lawnmower about once every 25 hours of grass cutting time (at least once a year)
  • Keep your lawn about 3 inches long
  • Mow your lawn at optimal times of day (8 am–10 am, 4 pm– 6 pm) to prevent turf stress

9. Dry weather

Of course, dry weather can also cause your grass to look yellow. Cultivating a healthy, deeply-rooted lawn will allow your lawn to thrive—even in hot, dry weather conditions. To prevent your lawn from drying out during hot summer temperatures, follow the watering guidelines outlined in previous blog posts.

 

Still not sure why your lawn is yellow? Could your lawn benefit from top quality fertilizer applications and grub control? Stewart’s Lawn Service is for you! Call or text 801-226-2261 today for a free quote and more information.

 

Check out our Lawn Watering Guide Video: