Why Is My Grass Turning Yellow?
Maintaining a grass lawn can be filled with unexpected difficulties, from weed control to length maintenance, watering, and more. One common grass issue that lawn owners deal with is yellowing, which may occur in select areas or affect the whole lawn. But why does grass turn yellow, and how can you identify the cause(s)?
Grass often turns yellow due to environmental conditions, such as too much or not enough water, the spread of fungal diseases, and backyard runoff from pet excrement. Sometimes, the problem boils down to a combination of more than one of these factors.
Published: January 13, 2023.
To learn more about why your grass might be turning yellow, keep reading. We will highlight the different factors at play in many residential lawns that contribute to this change in grass health and color. Without further ado, let’s dive into the reasons!
Overview - Reasons for Yellowing Grass
There are many possible reasons that grass develops yellow spots or even turns completely yellow all over. In this guide, we’ll be exploring the following environmental factors - both natural and man-made - that often lead to the yellowing of grass.
1. Wilting from drought conditions and how to identify it
2. Wilting from dog urine or feces and how to identify it
3. Drowning from overwatering and how to identify it
4. Drowning from lack of irrigation/drainage and how to identify it
5. Yellowed tips from frost burn and how to identify it
6. Yellow patches from fungal diseases and how to identify it
7. Yellowing from lack of nutrients and how to identify it
8. Yellowing from too much nutrients and how to identify it
9. Yellowing from clay/dense soil and how to identify it
10. Yellowing from overly acidic soil and how to identify it
1. Drought Conditions
Most people automatically assume that drought is the cause of yellowing grass, and it can be (in some cases).
Whether brought on by lack of watering or climate conditions, drought can cause the grass to turn yellow because the blades become dry and start dying. If this is the case, it may be a sign that your grass is on its way to turning brown.
If you want to understand the science behind this cause-and-effect, you can consider how chlorophyll changes during drought.
Chlorophyll content - the green pigment in plant life that makes it appear green - can decrease when a plant is undergoing drought stress.
There are a couple of different indicators that your grass might be yellowing due to drought conditions, including:
- A notable and prolonged change in weather conditions (hotter, dryer)
- A very low amount or complete lack of shade over your lawn
- You have been watering the grass mainly during full sun or not enough
- Your grass is both yellow AND dry
2. Dog Excrement
If your lawn sees a lot of dog traffic - especially dog bathroom breaks - then chances are you have urine and feces sitting on your grass and leaking into the soil. Here’s why this is a problem that can lead to grass yellowing.
Dog urine has a considerably high concentration of nitrogen in it. And although nitrogen is an essential soil nutrient for grass, too much can lead to poor grass health. For example, the excess nitrogen can actually burn the grassroots.
In this unhealthy state, the grass will change in pH level and other conditions, leading to a yellowing color.
It’s fairly easy to identify grass that has turned yellow from dog excrement. If you don’t have any dogs leaving waste on your lawn, then you can ignore this section.
But if you do have dogs leaving waste on your lawn, then look for spots or patches of yellow grass surrounded by green grass.
Just as too little moisture can adversely affect grass, so can too much moisture. Overwatering can happen naturally due to the precipitation levels where you live, or it can happen because of your own human error.
Similar to the relationship between drought stress and chlorophyll levels, there is a relationship between water stress and chlorophyll levels in plants.
The stress from too much water changes photosynthesis, resulting in yellow grass rather than green grass.
Furthermore, overwatering causes grass roots not to grow and develop as they should, as it cramps out a room in the soil that should be for oxygen.
A bad root system leads to unhealthy grass, which in this case, causes yellowing.
If you want to determine whether or not overwatering is causing your yellow grass, consider the following:
- Has there been an increased and prolonged change in rainfall and humidity where you live?
- Have you been watering your lawn more than directed for your growing region?
- Are the blades of grass also thinning as they yellow?
These could all be signs of overwatered, yellow grass.
4. Poor Irrigation
This factor sort of ties in with overwatering or overly wet conditions. Poor irrigation, including soil that doesn’t drain as well as it should, can cause water to pool up in certain areas of your lawn.
These areas will be the most affected by yellowing for all of the water-related reasons mentioned above.
You may have irrigation issues if there are sunken places in your lawn, areas with aggressive shading from a treeline, or an odd incline.
Poor irrigation may be the cause of your yellowing grass if you notice that your grass is far more wet and yellow in shady areas. It may also be the source of your problem if you have areas where you can visibly see pooling water or puddles that don’t evaporate in full sun conditions.
It’s important to identify this issue, as it can lead to worsened grass health when the moisture causes disease.
5. Frost Burn
Frost burn is a unique condition that may be affecting your grass, turning it yellow or yellowish-brown. It’s worth noting that frost burn isn’t likely to kill your grass completely, but it will impact its growth and color.
Basically, in frost temperatures, blades of grass can freeze, causing the water inside them to expand. This leads to splitting damage and further vulnerability if that grass gets stepped on.
As a result, the damaged grass may briefly turn yellow before moving on to a brown color.
One way to identify frost burn is to consider the species of grass your lawn has. Warm-season grasses such as St. Augustine grass and zoysia grass are particularly vulnerable to changing temperatures and frost burn.
Furthermore, you can check the weather report to see if temperatures have recently fallen below freezing or caused a frost. This type of yellowing is more on the brown side than others.
6. Fungal Diseases
Another common issue that grass faces is the spread of fungal diseases. Plants become vulnerable to certain diseases when they’re put in certain non-ideal conditions like too much moisture.
The health compromise often leads to patches, blades, or spots that yellow or turn brown.
Here’s how to identify certain common grass fungal diseases that cause yellowing:
- Dollar Spot Disease - The grass develops straw-yellow spots and has a water-soaked appearance and cobweb-like growth
- Rust Lawn Disease - The yellowing occurs in patches of thinning grass, eventually changing to rust-colored
- Summer Patch Disease - The yellowing occurs as 2-inch wilted patches of grass that turn yellowish-brown and grow, often starting at the tips
- Necrotic Ring Spot Disease - The yellowing starts as a yellow/light green color on thinning grass, followed by a 3-15” ring pattern
- Red Thread Disease - The yellowing starts as a reddish color, eventually turning into yellowish, bleached patches of grass
- Slime Mold Disease - The yellowing appears as a yellowish slime on the grass that turns gray and powdery over time
7. Lack of Nutrients
A healthy lawn needs plenty of nutrients to thrive, but not just any nutrients. Specifically, most grasses require a blend of N-P-K (nitrogen-phosphorus-potassium). Depending on the species and your growing region, this blend will vary.
But a lack of, say, potassium may cause grass health to decline and lead to yellowing blades or patches. Potassium also helps to protect grass against environmental stressors that can turn it yellow, so having enough potassium is crucial.
For example, with turf grasses, you tend to need more potassium in the nutrient mix.
It’s hard to identify a lack of nutrients as the problem by merely using your eyes or checking your gardening patterns. In this case, you’ll want to do a nutrient test of your lawn’s soil to determine the NPK ratio and compare it to the standard for your growing zone.
There are easy-to-use home test kits than can be found in local garden centers, or they can be ordered from online stores.
8. Too Much Nutrients
On the other hand, your lawn may be yellow and suffering from too much of certain nutrients. Again, there is a delicate balance of NPK that is unique to different types of grass in different regions.
Too much nitrogen is a common culprit when it comes to nutrient problems and yellowing grass. As mentioned before, this happens a lot with frequent dog urination on a lawn.
But it can also occur if you live in a region where the soil is naturally high in nitrogen and you’ve been supplementing the soil with more nitrogen.
For example, soil that is high in humus and crop residue is often rich in nitrogen as well.
However, damage from too much nutrients can occur when fertilizing the grass - the gardeners can accidentally spread fertilizer unevenly over the lawn, causing too much fertilizers in certain areas, which will cause root burns, yellowing, and drying out of the grass.
Again, a solid way to identify an excess of certain nutrients in your lawn’s soil is to do a home test. This is the best way to determine whether or not an imbalanced NPK ratio could be turning your grass yellow.
9. Clay or Dense Soil
Dense soil, compacted soil, and soil rich in clay content can all contribute to grass yellowing. This is due to the nature of the soil beneath the grass and its inability to allow grass roots to spread and grow as they should.
It also keeps grass roots from traveling as deep as they should to strengthen the plant and receive plenty of nutrients.
As a result of this poor root system, grass becomes weak, stunted, and in many cases, yellowish in color.
There are some pretty straightforward ways to tell if your soil is too compact for grass to grow well. One big tell is the presence of pooling water or overly wet grass - which is due to the poor drainage that compact soil causes.
Another way to tell is to stick a spade into the soil and observe it. If it’s largely clumpy, hard, or even gray, it’s probably too compact.
10. Too Acidic
Last but not least, you should consider the possibility that your lawn’s soil is too acidic to accommodate healthy grass. The pH level of grass depends on the species and your growing region.
For example, most healthy lawns should have a neutral or slightly acidic pH. But if your soil is too acidic, the grass could turn limp and yellow, often resulting in thin patches or bare patches. Luckily, it’s not a type of damage that grass can’t recover from.
You may be able to identify acidity as the root of your problem by testing a soil sample for its pH level. Compare that number to the pH level that the specific kind of grass ought to be.
You may also be able to tell if acidity is the problem based on pollution in your region or the nearby decomposing vegetation. Both of these factors can increase acidity in your lawn’s soil.
If you’ve ever wondered why my grass is turning yellow, take comfort in the fact that you’re not alone.
Grass can turn yellow for a variety of reasons, ranging from drought to overwatering, nutrient imbalances, dog waste, pH imbalances, fungal diseases, poor irrigation, inadequate soil conditions, etc.
Make sure to refer to our guide to understand how your growing zone, climate, and grass type could lead to certain types of yellowing or unhealthy grass.