Lawn color changes can be a normal feature of turf management depending on your type of grass and climate, but they can also be a cause for concern. So what does it mean when you suddenly see your grass turning yellow? What could make grass black, white, or blue (hint: it could be lawn dye)? Understanding the cause of a color change, such as a white lawn indicating fungus or improperly applied herbicides, is the first step in correcting it. In this second installment of our two part blog series, we will look into four more colors that a homeowner might see develop in their fescue turf.
As we explored in the first part of this blog series, a lawn is made green by consistent access to key nutrients like nitrogen and iron. These nutrients are made available by fertilizer, but can and should also be built into the soil system for long term retention. The more a soil system is able to hold onto nutrients like these, the more it is available for the lawn to feed itself between fertilizer applications and retain that pretty green coloring.
However, there are many situations in which fescue turf doesn’t have correct nutrient availability:
- The lawn has not been maintained properly for some time.
- The property is newly built, and rich soil was lost during the grading process.
- The soil system is extremely sandy and low in organic material, leading to nutrients having fewer binding sites and leaching out more quickly.
- The property is being watered too much or there has been too much rainfall, causing nutrients to be flushed out of the soil more quickly.
- The lawn has poor root development, limiting the plant’s ability to absorb nutrients in general.
- The soil is significantly acidic, causing nutrients to be “bound up” in complex mineralizations that cannot be accessed by the lawn.
No matter the reason, the most common issue to occur when these key nutrients are lacking is a loss of that green lawn color. This most commonly manifests as grass turning yellow. Typically, this yellowing will occur in vast sections of the lawn rather than just select spots. If you see small yellow spots within otherwise green turf, it is more likely where your dog goes potty or something was spilled.
Unfortunately, knowing how to intervene with your grass turning yellow and instead returning to the green requires you to know why your grass is turning yellow in the first place. Having a thorough soil analysis done once every year or two aids in monitoring your soil quality as well as many nutrient levels. Then, a strong professional turf management program can be employed to remedy the issues in your yard that are causing nutrient deficiencies.
One of the most alarming situations for a client of a lawn care company is when they have to call in and ask, “Why is my lawn black?” Surely, black is a bad news lawn color for any type of grass! It may come as a surprise, but while black is definitely an uncommon color for a lawn, it is actually not nearly as concerning as most of the other colors we have been discussing. For the most part, there are two reasons that a lawn may develop black coloring in the grass.
First, black spots in a lawn can be commonly caused by a summer fungus known as slime mold, pictured above. Like most lawn fungal issues, slime mold likes warm, humid conditions. Slime mold on grass is almost always a purely aesthetic problem as the mold does not do any direct harm to the turf. In the most extreme situations, heavy development of the mold can disrupt the turf’s ability to photosynthesize, but this is fairly uncommon. For most homeowners, slime mold is just a funny looking nuisance, but it is fixed easily by just washing it off with a water hose.
Second, larger expanses of black in a lawn may be caused by a fertilizer application rather than a natural fungus in the ecosystem. When nitrogen isn’t ideal for a lawn, a form of iron can also be applied to turf areas to promote a darker green coloring. However, like with any type of fertilization, it can work a bit too aggressively when first introduced to the lawn system. While the overapplication of nitrogen and other products can “burn” the grass and turn it brown or yellow, too much iron can blow past the green goal and dive straight to a black coloring. Again, if this happens, don’t worry. While it looks strange, most of the time it will fade within a couple of weeks and return to normal.
On the opposite side of the lawn from grass that has turned black is the possibility of grass that has turned white. Similarly, a white lawn is typically caused by one of two primary sources: fungus, specifically one known as pythium blight, and treatments, specifically ones that utilize the active ingredient mesotrione. White from this herbicide is normal, but white from pythium blight can be a serious problem for fescue turf.
Typically, pythium blight is an issue most common in cool season grasses like bentgrass, bluegrass, and ryegrass. While it is less common in fescue turf, it can still appear now and then when the conditions are just right at the peak of summer. Even though pythium blight acts similarly to other fungal diseases like brown patch and grey leaf spot, it is most easily recognized when the mycelium of the fungus are visible. The mycelium of pythium blight generally have a cotton-like appearance and are light grey or white in coloring. Because this disease can be aggressive and destructive, intervention with a fungicide is almost always necessary to prevent substantial turf loss.
Mesotrione, most often seen in the herbicide known as Tenacity, is used by turf management professionals most often for late summer weed control in fescue lawns. It is an appealing option because of its efficacy as well as its safety for use close to the application of fescue seed. In some situations, it can also be used as a pre-emergent.
The mode of action for mesotrione is to in a sense “bleach” the targeted plant, preventing its ability to photosynthesize and killing the weed as a result. As pictured above, when large areas of a lawn are overtaken by weeds such as crabgrass, the yard’s treatment with this product can result in a startlingly white lawn. To strong or frequent applications can have this effect on the fescue itself as well, but this almost always grows itself out and becomes a nonissue.
No, in this situation, we’re not talking about bluegrass turf, and we’re definitely not talking about bluegrass music! Depending on where you live, you may have seen lawns that literally have blue grass. If a property is being professionally maintained, they may be receiving liquid applications that have included a lawn dye, the most common color of which is blue.
Lawn dye is used by turf management professionals to make it easier to see that a liquid treatment of fertilizer or weed control has been applied to the yard. Not only does this give a client confidence that the treatment was done, but it also helps a technician see where they have and have not sprayed their product. For cost and aesthetic reasons, not many companies use a lawn dye, but there are some that have made it their signature.
Lawn dye in this scenario is typically designed to fade and wash off within a few days. Because its purpose is to significantly alter the lawn color for best visibility, blue and red are most commonly the colors of choice. To a much greater extent, this is a similar process to the colored markings applied to athletic fields most of the time. Some homeowners are even beginning to have their dormant lawns dyed green! Either way, coloring like this is almost always intentional and no cause for concern.
Monitoring your lawn color is one of the key ways you can stay up to date on changes in the health of your yard. The goal is always green, but every lawn will go through some period in which it turns brown, red, purple, yellow, black, white, or even blue. Every color you might see in your grass means something, which is why it is invaluable to know what those meanings are.