What Makes Grass Yellow and How Do I Fix It?
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If you're seeing patches of yellow grass in your otherwise lush green lawn, here's what might be happening and how to fix it.
6 Common Reasons Grass Turns Yellow
It happens to most of us. You think you have this lawn care thing figured out. Then you notice “yellow” grass disrupting your masterpiece. Worse, the blemish seems to be taking on a life of its own.
Here are six things that can make your green grass turn yellow, plus a few solutions and tips for how to fix them.
Let’s start with a common culprit. If your dog always does its business in the same area of your lawn, you’ll probably start seeing the grass turn yellow. Dog urine contains salt. In high concentrations, salt kills grass. These dead areas usually show up in the spring after the snow melts and the rest of the grass begins to green.
- Remove the dead grass.
- Work up the exposed soil using a tool, such as a Garden Weasel Cultivator.
- Apply a generous amount of gypsum, such as Encap Gypsum Plus AST. Work it into the top two inches of soil. This will help neutralize the salt damage.
- Flush the spot with lots of water. This will help get the gypsum deep into the soil.
- Once the soil is workable, overseed with a quality grass seed mix such as Scotts EZ Seed Patch and Repair. This is a convenient all-in-one kit that contains seed, mulch and a little fertilizer.
Compacted soil can cause all sorts of lawn problems. Vehicles, construction machinery and even lawn mowers following the same cutting pattern week after week are major culprits. Compaction squeezes pore space from the soil so it can’t absorb critical life support elements like water, nutrients and oxygen. When that happens, your grass suffers and can turn yellow as a result.
- Rent a core aerator for around $65/half day.
- Aerate when the soil is moist, not wet. Soft soil allows for deeper penetration of the coring tines. Make several passes over the yellow grass punching as many holes in the area as possible. Don’t worry, you won’t harm the grass by aggressively aerating. Keep going until you see at least 12 holes per square foot of lawn.
- After they have dried, gently bust up the cores and work them back into the grass. A rake similar to the True Temper Steel 16-Tine Bow makes this job easy.
- Reseed the area with a quality seed mix suited for your climate and site conditions.
- Lightly top dress the seeded area with weed-free soil or compost.
- Water lightly and frequently as grass germinates and begins to grow.
- If possible, soak up any remaining liquid on the surface by applying a highly absorbent material such as kitty litter, sawdust or calcined clay, such as Turface MVP. Place in a plastic bag and dispose.
- You may be tempted to flush the spill area with water. Don’t! Flushing the area will only make the problem worse by spreading the chemical over a larger area.
- You’ll want to dig out the contaminated soil to a depth of six to 10 inches. How deep you need to excavate will depend on how deep the pesticide soaked into the soil.
- Backfill the hole with weed-free soil.
- Reseed the area as described earlier.
Grubs and Insects
Grub infestation can result in yellow grass. These tiny c-shaped “worms” (the larvae stage of many beetles) invisibly munch away at grass roots, severing them from the blades of grass above ground. Other insects, like chinch bugs and sod webworms, can feed on grass blades rather than the roots, killing your grass from the top down. Both grubs and surface-feeding insects can kill or severely damage your lawn, turning it yellow.
- Grubs can cause severe damage if left unchecked. Applying a preventative insecticide in early summer will keep them at bay. Grub control products that contain chlorantraniliprole, such as Scotts GrubEx1, do a great job and are pollinator-friendly, meaning they won’t harm bees, butterflies and other beneficial insects. Please strongly consider using a grub preventer containing this active ingredient. They’re much safer for the environment, humans and pets.
- Tiny insects can be hard to see. One way to determine if you have a heavy infestation of lawn-chewing insects like chinch bugs is to cut out the bottom of a coffee can, push it into the grass and fill it with water. Let the water soak into the ground (put a few drops of dish soap in the water to speed up the process). As the soapy water permeates the soil, the bugs will float to the surface of the water remaining in the can. How many bugs you see will help you determine if you have a chewing insect problem and how bad it is.
- Using safe lawn insecticides containing bifenthrin, such as Ortho BugClear Insect Killer for Lawns & Landscapes or Talstar Xtra Granular Insecticide, will provide good results when eliminating chewing insects.
- Most grub control products only work on grubs, so know which insect you’re targeting and choose your product wisely.
Lack of Nitrogen
Your lawn needs to be fed, just like you. When grass turns yellow, it may simply be hungry. Nitrogen, the first number of the fertilizer analysis, is what makes your lawn green. It’s an essential nutrient to keep your grass dense, weed-free and actively growing.
- Use a lawn food that contains a high percentage of nitrogen, such as Pennington UltraGreen Lawn Fertilizer. It contains a lot of quickly available nitrogen fortified with five percent iron, which also turn your grass green. If you’d rather go the organic route, Milorganite Organic Nitrogen Fertilizer will green up your lawn nicely as well. It also contains a healthy dose of iron. (Note: Milorganite contains phosphorous. Some states and local regulations ban the use of phosphorus in lawn fertilizers. Check your state and local restrictions before using any lawn fertilizer containing it.)
- After applying fertilizer at the recommended rate, water it into the grass to activate. Then watch your lawn start to green up!
Too Much or Not Enough Water
Too much or not enough water can turn your lawn yellow or straw-colored. Too much water can drown grass roots and rob the soil of oxygen and that lush green color. Too little water will create drought symptoms that turn your lawn yellow or some shade of brown.
- Pay attention to the amount of water your lawn gets. That’s easier to do if you run an automated irrigation system. You can adjust the frequency and amount of water to fit weather conditions and the time of year.
- Pay attention to how often your system goes on. If it runs when it’s raining or when the ground is already moist, adjust the clock timer so you’re watering less frequently. Consider buying a simple and inexpensive soil moisture probe, such as the Sonkir Soil 3-in-1 Soil Moisture/Light/pH Tester, to make sure you’re not under- or over-watering.
- If you don’t have an automatic irrigation system, managing soil moisture can be a challenge. Focus your efforts on watering the dry, yellow grass. No need to water the entire lawn. There are many hose-end sprinklers to choose. Select a model that best covers the shape and size of your dry area. You can also consider a smart sprinkler that can automate your hose-and-sprinkler lawn watering process for you.