Different shades of green in lawns can be caused by something simple like uneven watering patterns or something more malicious like root rot or chemical runoff. Whatever the case, below are over a dozen reasons your lawn might have an uneven color and some suggested first steps to help get things to where you want them to be.
Why Is My Grass Different Shades of Green?
Deficiencies like lack of light, water, or nutrients are the most common causes of different shades of green in lawns. However, parasites like webworms, thrips, mold, and more can also cause these conditions. Even if your lawn is a patchwork of colors right now, it can get to an even shade of green with the right tools and information.
Reasons for Light Green Grass Patches in Lawn
Light green patches are often harder to treat and diagnose than dark green patches of lawn, but that’s only because there are so many causes. However, each cause has its own set of signs and symptoms. The list below should help you narrow down your options for treating light green grass patches.
Lack of Light
Grass and plants of all types need at least a little sunlight to survive. While certain varieties are capable of thriving in low light conditions, not all grass types will look their best if they’re in full or even dappled shade.
If you know what grass type you have, consider looking up its light requirements. If it needs more sun, consider removing the lower branches of shade trees or having them professionally pruned to let more light through. If there is still too much shade in your yard, you may have to switch to another grass type or a mix to achieve a more even appearance.
Lack of Nitrogen
Nitrogen is one of the primary ingredients in general grass fertilizers. It’s what grass needs to grow, replenish lost energy, and heal if damaged. Low nitrogen can mean not only a loss of dark green color but it can also mean the grass is in a weakened state that can lead to disease.
Adding a high-nitrogen fertilizer, especially a slow-release fertilizer, can help correct this issue as soon as possible. Then, consider leaving any mulched-up leaves and grass clippings on your lawn during the last few mowings in the winter and the first few in the spring. This can help your lawn naturally retain nitrogen without the need for additional fertilizer.
Standing Water or Mud
Standing water can, in any grass type, lead to rot. This could be root rot, fungus and mold eating at stems and leaves, or rot of rhizomes and stolons as they become bloated with water and their cell walls are weakened.
Never water your yard if it has any sort of standing water or mud. To help it dry up, an aerating roller can be used to help encourage the water to drain. To prevent standing water in the future, pay attention to the topography of your lawn. Are there any natural impressions or low places where water tends to collect? If so, consider filling them in and replanting these areas to prevent more standing water issues in the future.
Fungus, Mold, or a Parasite
As mentioned above, standing water and all kinds of damp can lead to fungus, mold, and mildew. Other parasites can also be the cause of light patches in the lawn. Some insects and bugs like thrips and webworms can damage blades of grass in small patches and reduce the grass’s ability to retain moisture and nutrients. This leads to a change in color.
Look for any spores clinging to grass, web fragments, cocoons, or small gray specks that collect in the hairs on some types of grass. These are all signs of infestation from either mold or a parasite. Treatments include commercial fungicides and insecticides as well as making conditions inhospitable to whichever parasite you have identified as the potential culprit.
Chemical Burn
While uncommon, chemical burn from the over-application of fertilizer or lawn treatment sprays can also be responsible for “bleaching” your lawn in patches. These spills or over applications are also unlikely to remain contained to a specific area as many chemicals and fertilizers are quickly absorbed by grass and its root systems, spreading to surrounding grass clumps in as little as 4 hours.
If you have recently applied any substance to your lawn, double-check that it was added in the correct way and measurement. If it was added as instructed, was it added over any other substance? Could the active period of multiple chemicals have overlapped? This can also cause burning. Further, fertilizer cannot be applied with all herbicides and some other types of lawn treatments.
In all cases, the best first step is to dilute the potential chemical as long as your lawn is dry. Water your lawn evenly for 20 to 30 minutes. This should help the grass recover. Monitor its condition and, if the lawn is dry again in a few days, repeat this procedure until the grass is above 3” and needs to be mown.
Low Moisture Levels
Drought is a common cause of light green patches of grass. It can also cause yellow or brown patches of grass to be mixed in. If your ground is dry, water it deeply once a week or twice a week in hot weather in addition to normal, daily watering. Continue to do this until the ground retains some moisture every day.
A moisture meter is an inexpensive way to help monitor the level of moisture in the ground. If you have soil that is all or mostly sand, consider amending it or adding more organic matter over time to help improve water retention.
Damage from Improper Mowing
The ideal length for nearly any grass type is never shorter than 2”. For many grass types, allowing the grass to grow to 3” or more will help it better manage the water and nutrients it has on hand and allow it to be more resilient to disease.
If you have mown your lawn too short or “scalped” it, provide more water and, if possible, a light feeding of liquid fertilizer. This can help the grass recover more quickly and will reduce its chances of dying back.
Some Grass Types Are Pale Green When Healthy
While you may know that your primary grass type is supposed to be dark green, Poa annua, aka annual bluegrass, can easily invade a lawn and show up as “light green patches”. Centipede grass and zoysia grass are also common turfgrass types that are lighter in color than many others and that could intermingle with your primary grass type, creating different colored patches.
The treatment in this situation would be to identify and then remove the unwanted grass type. There are many ways to do this, including by hand or with the use of chemical sprays if the grass is of a different blade type or has a different growth habit than the grass you wish to keep.
Why Does My Lawn Have Dark Green Patches?
There are far fewer answers to the question, “Why does my lawn have dark green patches?” than there are to the question of light green patches of lawn. Below are the 3 most common reasons for dark green patches in a lawn. St. Augustine grass is particularly sensitive to all 3 of these conditions.
Fungus and Fairy Rings
One of the most common causes of dark green lawn patches is fungus in the thatch layer just on top of the roots of grass. Any type of grass that produces stolons aka “above ground roots” or tillers is most likely to develop this condition.
Once the fungus has fully saturated this layer and a thick, hydrophobic patch of ground has developed, it will put out small mushrooms at the edges of the dark green spot, aka the patch of fungus, to spread. These circles or mushrooms typically edge a fungal patch of about 2 to 3 feet in diameter and are commonly called “fairy rings”.
The fungus itself doesn’t harm the grass and will speed up the breakdown of thatch, boosting nitrogen levels in the area. However, as the thatch breaks down it, combined with the fungus, can create a hydrophobic condition meaning that water may not reach the roots of the grass near the center of the circle, causing it to die back and go from dark green to brown in a matter of 2 weeks.
The best method to cure your lawn of fairy rings is to rake up thatch and, if you intend to reuse it as lawn fertilizer, allow it to compost off to the side until you can add it later as a tea. After raking up the thatch, aerate the lawn. Continue to do so after each mowing until the rings no longer appear.
Standing Water or Mud
Standing water on your lawn is never a good sign. With many types of grass, the grass will look sickly when this happens. However, with St. Augustine or a stolon-type of grass, you’re likely to see the grass develop a dark green color as its roots decompose right before the grass itself turns brown and sludgy.
With standing water, the best thing you can do is aerate your lawn manually or chemically. Check to see that your lawn is level or that it has good drainage after each heavy rain as pockets can develop over time. Level these out where and when possible.
Underground Disease or Root Rot
Root rot can be caused by standing water, as in the example above, or by fungal infection, thrips, other insect pests, or bacterial disease. With any type of grass, the sudden decomposition of roots may make the plant look both dark green and dehydrated, a combination and symptom seen with almost no other condition.
Root rot is a tough problem to solve and you may need to bring in a local lawn care expert to help you diagnose your specific problem, if it’s not related to standing water or a local disease. Calling the local agricultural extension office can also get you pointed in the right direction as the people working there may know if there is a specific lawn grass disease in your area that may be causing your problem.
Other Reasons Why Your Grass Might Be Different Shades of Green
If, after reading the above two sections, you feel like none of those answers fit and are still wondering, “Why is my grass different shades of green?”, the following reasons and solutions may help as they cover broad problems that can cause both conditions.
Uneven Watering
“Why does my lawn have dark green patches?” is often answered when you see mushrooms popping up or when the grass suddenly turns dark brown after a brief period of green. However, it could also be a simple lack of water in some areas and too much water in others. Pay attention to where your irrigation system overlaps and see if any areas aren’t getting enough water.
Mixed Grass Types and Weeds
Light green grass patches in lawns are easily caused by mixing different grass types, especially warm-season grass types. The same can be said of dark green patches caused by planting St. Augustine mixed with another grass type in a wet area. Any two types of grass with different needs can end up competing with each other and creating patches of different colored grass in any lawn.
Nutrient or pH Imbalance
Grass needs more than just sunlight and water to survive. Though nitrogen imbalance is mentioned above, several other nutrients or the pH could be off. Inexpensive test kits are available to check the common nutrients and pH of your soil. This can be done in several places in your yard to see if the light green patches and dark green patches have different results.
Chemical Runoff or Overspray
While we all like to believe our neighbors consider how their actions affect us and our property when spraying their plants or lawns, this is often not the case. Through no malicious thought or action, runoff and overspray can cause unintended consequences, especially if you live downhill from anyone that uses lawn sprays and fertilizers frequently. If possible, try to coordinate your lawn treatments with these neighbors to avoid any accidental overdoses for your lawn or garden.
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