What Does Yellow Grass Mean?

Yellow coloration in your grass is a major sign that something is off, and it can be due to one of several different causes. Root damage, soil conditions, environmental stressors, disease, and nutrient deficiency are all potential causes of a green lawn turning yellow. A close inspection is important to determine the cause(s) to choose the appropriate solution(s).

How Do I Fix Yellow Grass?

Since yellow grass can be a sign of so many things, the right way to fix it will depend on the cause. For example, a nutrient deficiency should be tested for and confirmed before applying fertilizer. Compacted soil, on the other hand, should be aerated, then amended and fertilized as necessary. If a disease or pest infestation is damaging the lawn, those will require treatments followed by lawn repair. 

If you’re noticing a yellowing color to your grass, check from the roots up. If the roots are damaged, the blades will be damaged as well. You can do this by inspecting the base of the blades and checking for fungal growth or pests. If it’s discoloration and not an infection or infestation, try tugging at the grass. If the blades break easily, it may be weak from root damage. If it’s strong, it may be due to a lack of iron or nitrogen; a pH test should be done as well when you do a nutrient test before applying any fertilizer. 

The time of year will also influence which type of problem may be happening. Each situation will have its particular remedy, so identifying the cause is key to restoring the grass to a healthy lawn.

Why Is The Grass Yellow?

Yellow Grass

Yellow spots or widespread yellow grass can be a symptom of many different problems, including:

  • Low moisture
  • Compacted soil
  • Root damage
  • Nutrient deficiency
  • Frost burn
  • Fungal growth
  • Pests

Low Moisture

If the yellowing is occurring in the middle of summer in hot, dry conditions, your grass might be stressed by the heat and may be entering dormancy. If you haven’t been watering it enough, it should green back up with an increase in water delivery. Little moisture to the roots might also be happening if your soil is too compacted and not draining well, causing some roots to dry out and others to be saturated with water.

Compacted Soil

Soil that’s too dense or hard for moisture to penetrate will also make it challenging for grass to establish roots. Clay-heavy soils can be especially difficult since they will harden in heat or dryness and saturate with moisture when it’s wet. If your soil isn’t well aerated, grass that does make it in these areas might struggle more when conditions get dry and turn yellow or tan as the blades die off. Salt can also build up in soil that doesn’t drain it well and cause yellowing from overfertilizing with synthetics, or from winter salt applications.

Compacted soil also makes it difficult for grass roots to absorb nutrients, which are leached by water in the ground that roots take up. Using a core aerator and adding any amendments like sand or compost will allow air and moisture to penetrate and be held by the soil, which will better support strong roots and green blades.

Root Damage

When soil doesn’t drain well, moisture can build up at the surface level and keep the roots too wet for too long. If there is a lot of thatch in your yard, it can lead to humid conditions that provide breeding grounds for fungus, pests, or simple root rot from moisture buildup. Roots may also be damaged if a preemergent is applied and doesn’t drain properly, or if too much is put down. 

Like aeration, dethatching increases airflow, moisture penetration, and drainage from the surface level of the ground. Some thatch is good, but too much can lead to trouble. If your blades are yellowing from root damage, identifying the cause of the root damage, plus a repair and healing regimen, will get your lawn back on track to green.

Nutrient Deficiency

Milorganite 32 lb. Slow-Release Nitrogen Fertilizer

A lack of nutrients can lead to a lawn that isn’t as vibrant as you would want it to be. This is why soil profile tests are done before planting seeds or adding fertilizer: as plants deplete the soil over their growing season, much of the nutrients will need to be replaced for the next growing season. If the soil doesn’t have enough nitrogen, potassium, or other essential nutrients, it may not look its best.

A nitrogen deficiency or an iron deficiency are two main reasons your grass may be turning yellow. If there is widespread fading across the lawn, it’s likely a deficiency. A soil profile test will let you know if this is the case. Grass’ greenness comes from its chlorophyll, the green molecule in its blades that performs photosynthesis, and without an ample supply of nitrogen or iron, this main part of the plant can’t be produced and the blades will look yellow from deficiency. 

High soil pH, or alkalinity, causes iron to be bonded to other molecules and unavailable to be absorbed by plants. A pH level test with your soil profile will help you be sure the acidity levels are normal for your grass type, usually 5.5-6.5; anything higher may be too alkaline for iron and some other nutrients to be available.

Sometimes, however, too much nitrogen can be bad for a lawn. In mid-summer, when temperatures are high and the sun is strong, nitrogen can cause more growth than the grass would normally do in those conditions; too much growth may stress the grass and result in yellow, rather than green, coloring. Adding iron to green up your lawn will help chlorophyll production without the extra boost of growth that nitrogen supports.

Frost Burn

When a cool season grass grows in early fall, it will be mature by the end of the season when frost starts to occur at night. When grass seeds or sod are put down too late in the season, they’ll be growing later into the season than they normally would. The tips of the blades may get damaged by frost, and as long as there’s some green left on the blade, it should recover and grow on a normal schedule the following season. In winter, some yellowing or tanning is normal as grass enters dormancy.

Fungal Growth

Some grass may look yellow when the blades are infected by certain fungi. Two, in particular, rust fungus and brown patch fungus, turn the grass a dark yellow or light orange color. These usually develop under trees and in other shady areas in late summer and early fall when conditions are humid and moist. Ground that doesn’t drain well provides particularly supportive conditions for fungal growth.

Brown patch fungus shows up in patches, while rust fungus is a little more spread out. Both can be treated with fungicides and an increased mowing schedule, bagging all clippings to remove the spore-covered blades from the yard. Lawn diseases like these spread by fungal spores, or by viruses that may be transferred by insects.


Yellow and Brown Spot in Grass

Different conditions can attract different pests that can damage the roots and blades of grass, resulting in yellow coloration in some parts of the lawn. Dry conditions with lots of thatch buildup can attract chinch bugs, which eat the grass and weaken the blades. These insects will clear large patches of grass to the soil as they destroy the turf, and the edges will yellow.

Aphids can also cause yellowing to the grass as they eat the blades and damage the grass. These might be a sign of ants, which farm aphids in their tunnels for their sap. If it’s an aphid infestation alone, the sap, or honeydew, may build up and cause rotting on the grass which can also damage the roots. 

Depending on the insects and the level of presence and damage, solutions include home remedies like soapy water or vinegar, an insecticide product targeted for your specific pest, or contacting a pest control professional if the problem is something you can’t effectively deal with by yourself.