Ideally, a healthy lawn should be a vibrant shade of green. In extreme temperatures or times of drought, a bit of yellow or brown is to be expected. But the appearance of white grass can make even the experienced gardener scratch their head.
White grass is definitely not unheard of, and there are several reasons why your lawn could suddenly lose its normal color. The most common culprits include fungi, chemical damage, and nutritional deficiencies.
Don’t worry, however, because most cases of white grass can be treated. First, though, you need to determine what caused the color change in the first place. In this article, I’ll dive into the most common reasons for grass turning white and the best steps to take to get your lush green lawn back.
- 1. Powdery Mildew
- 2. Fusarium Patch Disease
- 3. Gray Leaf Spot
- 4. Side Effects of Herbicide
- 5. White Tips after Fertilizing
- 1. Dethatch your lawn
- 2. Apply a fungicide
- 3. Increase sunlight on your lawn
- 4. Use a slow-release nitrogen fertilizer
- 5. Adjust the soil pH to suit your turfgrass type
5 Reasons Why is my grass turning white?
In my experience, grass usually turns white as a result of fungal disease. Other likely causes include herbicide and fertilizer damage.
If the color of your lawn concerns you, I strongly suggest taking a closer look at the individual grass blades. Examining a few affected blades will give you a better idea of what could be to blame for the white color. For example, you may discover that the color comes from fungal growths rather than the grass itself.
From disease to chemical damage, here are the most common reasons I see turf grass turning white:
1. Powdery Mildew
When turf grass turns white seemingly for no reason, the most likely culprit is nearly always powdery mildew.
Powdery mildew is a disease caused by several fungus varieties — per Ohio State University, turf grass is generally affected by Erysiphe graminis. The disease can also impact ornamental shrubs, flowering annuals, vegetables, and houseplants.
Upon close inspection, individual grass blades carrying powdery mildew spores appear to be dusted with a fine white powder or chalk. As the fungus spreads, it will eventually cover large patches of lawn that appear powdery white from even a distance.
2. Fusarium Patch Disease
Fusarium patch, also known as Microdochium patch, is responsible for countless white lawns. Afflicted grass blades typically turn yellow but may appear white or pink when fungal threads are present.
Some people know this disease as pink snow mold. The term “snow mold” comes from the fact that the fungus responsible — Microdochium nivale — often spreads under cover of winter snow, only becoming visible when the snow melts in early spring. However, a layer of snow is not necessary for this disease to occur.
According to The Royal Horticultural Society, controlling the Fusarium patch is a difficult task for even experienced caretakers. Early identification and treatment are key to keeping this nasty infection at bay.
3. Gray Leaf Spot
While not as infamous as powdery mildew or fusarium patch, gray leaf spot is yet another fungal disease that can turn a lawn white. This particular infection is caused by the fungus Pyricularia grisea.
As the name implies, gray leaf spot produces light spots on individual grass blades. When enough blades are affected, entire sections of the lawn appear gray or white.
According to Clemson University, gray leaf spot most often affects St. Augustine grass but can be found on several other varieties as well. The fungus flourishes when moisture levels are high and night-time temperatures stay above 65°F. Spores can remain dormant in your lawn’s thatch layer and reappear when the conditions are right.
4. Side Effects of Herbicide
Mesotrione is a chemical herbicide that sometimes turns turf grass white. The most common brand name for this herbicide is Tenacity.
This herbicide works by blocking chlorophyll production and photosynthesis in weed leaves. However, it can also do the same to grass blades within the treated area.
When used as directed, your lawn should recover within a few weeks. The grass blades will continue growing and eventually, the white tips can be mowed off.
5. White Tips after Fertilizing
Many homeowners notice white grass shortly after applying fertilizer. There are a few reasons fertilizer could be the cause of your discolored lawn:
- High-nitrogen fertilizers may encourage the growth of fungi like powdery mildew.
- Many fertilizers contain built-in herbicides — fertilizer formulated with mesotrione can turn turf grass white.
- Excess fertilizer can burn grass roots and cause yellow, brown, or white damage to blades.
How to Treat White Grass in 5 Steps
For the best results, your treatment strategy should be tailored to your lawn’s specific needs as well as the root cause of the discoloration. However, a combination of some or all of the steps below should reverse most cases of white grass.
1. Dethatch your lawn
If your white lawn is the result of fungal disease, dethatching is a great first step. Thatch is a layer of dead grass tissue that builds up on top of the soil. Thatch is 100% natural — it can actually protect grass stems and roots in-climate weather — but can cause problems when allowed to grow too thick.
Excess thatch and fungi go hand-in-hand. Fungal spores, including those responsible for Fusarium patch disease, can lay dormant in the thatch for significant periods of time with no visible signs. Thick thatch also provides a safe place for fungi to overwinter (and attack your lawn the following year).
You can remove overgrown thatch using a manual or power rake. Particularly large lawns may call for a piece of equipment called a vertical mower or verticutter.
For most lawns, I recommend dethatching up to once per year. Avoid removing the entire thatch layer as this will expose the grassroots to the environment. Use caution when dethatching turf grass that spreads via stolons as the wrong technique could seriously damage the grass.
2. Apply a fungicide
Chemical fungicides may be necessary to treat white grass caused by a persistent fungal infection. However, there are a few things I want to cover before you continue with this treatment strategy.
First, you should ensure that your white turf grass is caused by a fungus. It is sometimes difficult to distinguish fungi signs and symptoms from other types of damage. If you’re at all unsure about your lawn’s diagnosis, I suggest reaching out to a local Extension Office or landscaping professional.
Second, I highly recommend trying to control the fungal disease using non-chemical means first. While fungicides can be extremely effective, they should be treated as a last resort when alternative solutions fail.
Once you confirm that a fungus is responsible for your discolored lawn and have ruled out other treatment options, you can move forward with the fungicide application. You’ll want to know which fungi species is to blame for your white grass so you can select a fungicide that will kill it. Fortunately, most fungi that cause white lawns are highly susceptible to standard fungicides.
3. Increase sunlight on your lawn
While not always possible, increasing the amount of sunlight your lawn receives each day can do a world of good against white discoloration. Sufficient sun exposure will keep many common fungi at bay. It also encourages healthy photosynthesis, which is crucial to maintaining a green lawn.
Some potential ways to increase sun exposure in your lawn include trimming overgrown trees and shrubs and moving portable structures like patio umbrellas.
If your lawn’s health issues are exacerbated by excess shade and there is no easy way to increase the available sunlight, I strongly suggest overseeding the area with a more shade-tolerant grass species.
4. Use a slow-release nitrogen fertilizer
Switching to a slow-release fertilizer may minimize the risk of root burn and decrease some fungal activity. But keep in mind that over-fertilizing is still possible even with a slow-release formula.
Sufficient moisture is just as important to preventing fertilizer burn as the type and amount of fertilizer used. Follow your chosen fertilizer’s application instructions carefully and ensure your lawn gets the recommended amount of water for the best results.
5. Adjust the soil pH to suit your turfgrass type
White or light green grass may be the result of an iron deficiency. In many cases, iron deficiencies are caused by overly alkaline soil.
Before attempting to fix your soil’s pH level, I recommend conducting a simple soil test and researching the ideal pH range for your grass type. Once you have this information, you can lower the soil pH slightly using elemental sulfur or aluminum sulfate if necessary.
Will white grass turn green again?
Whether or not your lawn immediately returns to its former green glory depends on the reason it turned white in the first place. In most cases, however, affected grass will recover with time.
If a layer of fungal threads or spores is to blame for your lawn’s color, then removing the fungus could be enough to restore its original color. If the blades themselves are discolored, you will need to wait for the damaged grass to be replaced with new growth.
The only time a white lawn wouldn’t eventually regain its color is if it has been damaged beyond repair. In such cases, reseeding with new grass is your only option. Before doing so, however, I highly recommend treating the area for the initial cause of your white grass. Otherwise, your newly planted lawn could fall victim to fungal infection or chemical damage as well.