Different colors of grass can be alarming when a homeowner sees their lawn go from green to something else. But what makes grass green, and what makes it change into red, purple, brown, or any other color? Understand the cause of a color change, such as seeing pink tendrils and identifying red thread disease, is the first step in correcting it. In this first installment of our two part blog series, we will look into not only what makes grass green, but different colors of grass like purple lawn areas and grass turning brown.
As you might remember from your biology class of long ago, in the simplest of terms, chlorophyll is what makes grass green. Chlorophyll absorbs most of the light needed for photosynthesis to occur, but it doesn’t absorb green light very well, which is why it’s reflected back as the color that we see. As a result, the green of your lawn is a good sign that photosynthesis is occurring and that your lawn is healthy.
That being said, just as certain nutrients make us put on weight or encourage strong hair and nails, certain nutrients for your lawn impact how green it is. The primary macronutrient most associated with how green a lawn stays is nitrogen. On a bag of fertilizer, nitrogen levels are indicated by the first of the three digits provided in the analysis (for example, 24-0-3, which would be a nitrogen focused fertilizer).
Nitrogen is typically applied to a fescue lawn at different levels through the growing season. A lawn is greenest when it is healthiest and happiest, which is why fescue lawns look so great in the spring and in the fall. Nitrogen applications should mirror this natural ebb and flow to prevent stressing the lawn. This is because nitrogen not only makes grass green, but it encourages faster growth above ground. During the summer, iron is a common micronutrient used to encourage a rich, dark green coloring because it is less aggressive in pushing growth as a side effect.
While there are different colors of grass even where green is concerned, with fescue and bluegrass holding a dark green coloring while zoysia and bermuda naturally tend toward a lighter or paler shade, green is always the goal for your lawn. A healthy lawn is a green lawn, so it is important to watch out for any colors that deviate from this standard. Let’s take a look at some other colors that are more concerning in a lawn.
If you see red or pink tendrils within areas of your lawn, it is most likely a sign of a fungal problem known as red thread disease. Red thread is most common in fescue lawns in the spring and early summer. While it isn’t technically the grass itself that is turning red, the name of this disease is quite literal in describing the red threads that develop within patches of browning turf.
While some lawn diseases like brown patch can be damaging to the fescue turf they infest, red thread is mostly a cosmetic issue and very rarely does any long term harm. It turns patches of turf a light brown color intermixed with the titular red threads, which is why these areas usually appear red or pink overall. Rather than being dead, this turf is just sick and will gradually grow itself out, returning to its normal green as the disease dissipates.
Typically, red thread is used as a diagnostic tool by turf management professionals to identify bigger problems. If a lawn develops red thread in the spring, it may have environmental conditions like humidity or thick growth that make it at greater risk of more serious diseases later in the season. Additionally, red thread disease is often associated with a lack of nitrogen, so it can reflect a soil system that is deficient in this key nutrient. Either way, red thread can be a surprise to homeowners who have never seen it before, but isn’t the worst on the list of different colors of grass.
Even though there are some types of ornamental grass that are intentionally purple, fescue is never one of them. A purple lawn should be considered a red flag by homeowners that their turf is experiencing a lot of distress and is on the edge of a total meltdown. This is because a purple or blue tint to a lawn is the first sign of heat stress.
Because fescue is a cool season grass, it is at its lowest and most unhappy point during the summer when air and soil temperatures exceed the ideal range for it. This is quickly exacerbated by a lack of shade, the development of drought conditions, and improper watering by the homeowner. By the time that daytime highs are in the 80s and 90s, many fescue lawns begin to struggle and shut down, which is commonly referred to as heat stress.
However, before a green lawn becomes a brown lawn, it goes through a period of looking more like a purple lawn. Purple is most often the color of stress in a lawn no matter what, but in fescue, this is most commonly associated with heat. If you see your fescue turning into a purple lawn, it is time to turn up the water! There is not anything that you can do about the air temperature, but you can take the edge off by keeping your lawn properly hydrated.
Of all the different colors of grass, brown should be considered the most alarming. Where most plants are concerned, brown is the color of death. A lawn should only be brown if it is a warm season lawn that has gone dormant for the winter. Otherwise, an investigation needs to be done as quickly as possible to identify the cause and begin a restorative solution.
As we discussed above, a lawn may have gone from purple to brown if it has succumbed to prolonged heat stress. When fescue goes brown from the heat, it enters a state of dormancy as a last ditch effort to outlast the extreme conditions. If things improve quickly with a break in the weather and improved watering from the homeowner, the lawn is able to recover, at least partially. However, without intervention, it is possible for whole sections of turf to die off completely.
Another common cause of browning in a lawn is the development of fungal disease. Problems like brown patch, grey leaf spot, and more are the result of overactive fungi doing damage to the tissue of the grass plants in a lawn. As these diseases take hold, they most often manifest as blotches, patches, or rings of brown within the otherwise green lawn. Many of these diseases can be devastating, which is why it is vital for a turf management professional to intervene quickly with an appropriate fungicide.
While heat stress and fungus are two of the most common causes of grass turning brown, there are many others that should be considered. A few issues include:
- A shallow obstacle below ground impeding root development
- Grubs or other insects doing damage to the turf’s roots or foliage
- A chemical treatment that was mixed or applied wrong
- Large areas of weeds that were intentionally treated and have died
- Heavy objects like a toolbox or a tarp that were left on the lawn
- Improper mowing that has taken too much grass off at once
There are even more examples than these, but the variety of causes is why it’s important to carefully consider the big picture when you see grass turning brown.
With so many different colors of grass, there are a lot of opportunities to become a better practitioner of turf management through improved diagnostics and treatments. In the next installment of this series, we will take a look at four more colors and discuss what it means when you see black, white, yellow, or blue in a lawn.