Why Grass Turns Yellow

In the vibrant world of greens, a patch of yellow grass can be an eyesore. As homeowners, we take pride in our lush lawns and constantly strive to maintain their health and beauty. But there are times when, despite our best efforts, we notice a disheartening change – our normally green grass starts to turn yellow. This transformation not only detracts from the aesthetic appeal of our outdoor spaces but also signals potential underlying problems. If you’ve ever wondered why grass turns yellow, you’re in the right place. This article will delve into the reasons behind this colour shift, providing insights and solutions to restore your lawn to its former glory.

Watering Woes

There’s a delicate balance when it comes to watering your lawn, and tipping the scales in either direction can result in yellowing grass. Overwatering is a common issue, often stemming from the misconception that more water will create healthier grass. But in reality, excessive watering can cause the roots of your grass to become waterlogged, depriving them of much-needed oxygen. This lack of oxygen inhibits the grass’ ability to absorb nutrients, leading to a yellow or even brown appearance.

On the other side of the spectrum, underwatering your grass can also lead to yellow patches. Grass requires consistent moisture to maintain its vibrant green colour and overall health. If it doesn’t receive enough water, the grass can become dehydrated, causing it to turn yellow as it struggles to conserve resources. It’s important to remember that the amount of water your lawn needs can depend on various factors including the type of grass, the season, and the local climate. Finding the right balance is crucial to keeping your lawn lush and green.

Nutrient Needs

why grass turns yellow
Photo by Bharath Raj N on Unsplash

Applying fertilizer to your lawn can sometimes have unexpected consequences, such as causing your grass to turn yellow. This is often due to a condition known as fertilizer burn, which occurs when too much fertilizer leads to a buildup of salts in the soil. These soluble salts can inhibit the grass’s ability to absorb water, resulting in yellow or even brown patches. The overuse of nitrogen-rich fertilizers, in particular, can make the soil acidic and contribute to this issue.

On the flip side, under-fertilizing can also lead to yellowing grass. If your grass is not receiving enough nutrients, it may begin to show signs of nutrient deficiency. For instance, low levels of nitrogen and iron, essential nutrients for the health and colour of your grass, can cause it to turn yellow. The key to effective fertilization is balance. You want to provide enough nutrients for your grass to thrive without overwhelming it with too much of a good thing.

Disease and Pests Dilemma

Lawn diseases and pests are significant contributors to the yellowing of grass. Many lawn diseases that cause yellow spots are often fungal. These include conditions such as Dollar Spot, where lawn patches appear small, circular, and sunken. Individual blades may have a straw-coloured band across the leaf blade. When it comes to pests, grubs are a common problem. These beetle larvae feed on grass roots, causing large patches of the lawn to turn yellow and eventually brown. Overwatering your lawn can also lead to an increase in fungal diseases and insect infestations due to reduced resistance in the grass.

Fungal diseases, in particular, can rapidly spread and cause lawns to turn from yellow to brown if left untreated. The temperature, thatch, and moisture levels all affect your lawn’s susceptibility to these diseases. On the other hand, pests can damage the roots of your grass, leading not only to yellowing but also to the death of the grass in severe cases. Proper lawn maintenance, including appropriate watering, mowing, and fertilization, can significantly reduce occurrences of yellowing grass due to disease and pest infestations, maintaining the health and vibrancy of your lawn.

Mowing Matters

The act of mowing your lawn, while seemingly simple, can greatly impact the health and colour of your grass. One common reason why grass turns yellow after mowing is due to the actual sheaths of the grass blades. These sheaths are typically yellow or tan in colour, and when you mow, you’re cutting off the green leaf blades and exposing these sheaths.

If done properly, mowing should only remove a portion of the green leaf blades, leaving enough green for the grass to continue photosynthesizing light effectively. However, if cut too short, new grass can turn yellow due to a lack of moisture. It’s best to let the grass grow a bit longer before cutting it to ensure it retains sufficient moisture 

Another reason why your lawn may turn yellow after mowing is related to the stress inflicted on the grass from improper mowing practices. Mowing too high or too low can cause your lawn to suffer from stress or a lack of nutrients from oxygen and sunlight. Moreover, an often overlooked mowing mistake that causes yellow grass is scalping, which refers to cutting the grass too short. When you scalp the lawn, you’re essentially depriving it of its ability to photosynthesize properly, which can lead to a yellowing appearance. Furthermore, if you’re using a mower with dull blades, it can tear the grass instead of making clean cuts, leading to damaged and yellowed grass blades 

Weather Woes

Weather conditions can significantly influence the health and colour of your grass. Intense heat and extended exposure to sunlight throughout the day can accelerate the drying out of your lawn. This heat stress results in yellow areas as the grass struggles to conserve its resources under intense temperatures. In addition, sudden and dramatic changes in the environment, like heavy rainfall, can also lead to yellowing. The reason is that intense precipitation can dilute and wash away essential nutrients in the soil, leaving the grass malnourished and causing it to turn yellow.

On the other hand, frost burn is another weather-related issue that can cause your grass to turn yellow. During frosty conditions, the ice crystals can damage the grass cells, leading to discolouration. Furthermore, prolonged periods of frost can cause extensive damage, turning large patches of your lawn yellow or even brown. Although grass can often recover from short periods of frost, long spells of cold weather can cause lasting damage. Understanding these weather impacts can help you take preventative measures to maintain your lawn’s health and vibrancy, regardless of the season.

Turning the Tide: Greening Your Lawn

Having identified the potential causes of yellowing grass, let’s discuss some remedies:

  • Water Wisely: Make sure you’re watering your lawn appropriately. The exact amount of water needed will depend on your type of grass, but generally, your lawn should receive 1 to 1.5 inches of water per week.
  • Fertilize Fairly: If nutrient deficiency is the issue, consider using a fertilizer that replenishes the soil with the required nutrients.
  • Pest and Disease Defense: Regularly check your lawn for signs of disease or pests. If you find any, consider using a lawn fungicide or pesticide.
  • Mow Mindfully: Avoid mowing your grass too short and ensure your mower blades are sharp.
  • Patience During Extreme Weather: If your grass turns yellow due to extreme weather conditions, patience is key. Once the weather normalizes, your grass should regain its green colour.

In a nutshell, maintaining the lush green appearance of your lawn can be a delicate balancing act. Both watering and fertilizing require a careful hand to ensure that your grass is neither overwatered nor over-fertilized, as both can lead to a yellowing lawn. But remember, these aren’t the only factors at play. Other issues like disease, pests, or weather conditions can also contribute to a yellow lawn. By understanding these potential problems and how to address them, you can take proactive steps to keep your lawn healthy and vibrant. So next time you see a yellow patch in your lawn, do not worry. With a little knowledge and care, you can bring back the green.


Q: Why does my grass turn yellow after I mow it? 

A: The act of mowing can expose the yellow or tan sheaths of the grass blades, leading to a yellow appearance. Additionally, cutting your grass too short can stress the lawn and deprive it of its ability to photosynthesize properly, which can also lead to a yellowing appearance.

Q: How do weather conditions affect the colour of my grass? 

A: Excessive heat can cause the lawn to dry out quickly, leading to yellow areas, while heavy rainfall can wash away essential soil nutrients, causing the grass to turn yellow. Frosty conditions can also damage grass cells and cause discolouration.

Q: What measures can I take to prevent my lawn from turning yellow? 

A: Maintain proper mowing practice, ensuring your mower blades are sharp and you’re not cutting the grass too short. Monitor weather conditions and water your lawn accordingly to prevent it from drying out in hot weather or being overwatered during heavy rainfall. During frosty conditions, consider protective measures like covering your lawn with a frost blanket.

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