If there are large areas where the grass in your lawn is green at the top but brown at the base of the blades, there are a few possible culprits. These include:
- Excessive thatch buildup
- Nutrient deficiency
- Too much or too little water
- Unbalanced soil pH
- Slow spring green-up
All of these conditions can be remedied naturally, returning your grass to a vibrant green from the tip of the blade all the way down to the soil.
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6 Reasons Your Grass is Green at the Top but Brown Beneath
Grass that is green at the top of the blade but has begun to turn brown or yellow toward the bottom is a unique case with specific causes. The first step is to rule out what you know is not the cause of this development. The following can be eliminated from the suspect list:
- Fungus: Causes brown patches in your yard, or completely brown grass blades. You can rule this out.
- Grubs: Cause dead grass to form in patches. Again, the grass will turn completely brown. This can be ruled out as well.
Now that we know what isn’t causing this green on top, brown beneath issue in your lawn, let’s move on to find out why is your grass green on top but brown underneath.
Too Much Thatch
Thatch is the buildup of slow-decomposing grass stems and runners that forms between your growing grass and the soil. Thatch is brown in color and contributes to the unsightly look of a yard that is green on top but brown underneath. It also chokes out your grass. In order to see if you have too much thatch:
- Dig up a small section of your yard, about 3 inches (7.5 cm) square and 3 inches deep.
- Measure the thatch layer (brown, dead material between growing grass and soil).
- If the thatch layer is more than 0.5 inches (1.5 cm) thick, thatch buildup should be removed.
- If the thatch layer is less than 0.5 inches thick, it is healthy and you can rule this out as the cause of your lawn’s woes.
In the case of thatch buildup greater than 0.5 inches, rent a dethatcher from your local hardware store and thoroughly dethatch your yard. You’ll soon have a much greener, healthier lawn.
Your Lawn Needs Fertilizer
A nutrient-starved lawn will struggle to maintain color and may begin to turn brown, starting at the base of the grass blades. To restore nutrients and color to your yard, do the following:
- Spread a natural fertilizer with iron on the lawn.
- Water fertilizer into the soil.
- Allow 7 days for fertilizer to feed your lawn and improve color.
Fertilizers rich in iron improve grass coloration, and a slow-release nitrogen fertilizer will stimulate grass blade growth, turning those brown lower portions of your lawn green again.
Drought conditions cause grass to die or enter dormancy. This can be the cause of the initial browning of the lower portions of the grass in your yard. To determine if grass discoloration is caused by insufficient irrigation, check for these signs:
- Inspect the grass closely. Are the blades folded as well as turning brown? This is a sign of dry soil.
- Push a screwdriver into the soil. If it is difficult to push 4–6 inches (10–15 cm) into the soil, it’s too dry.
- Are footprints visible on your lawn long after walking on it? Grass that doesn’t spring back is suffering from a lack of water.
To correct a lack of water, increase the duration of your watering sessions. Watering your lawn deeply 1–2 times per week will yield the best results.
Much like drought conditions, an overabundance of water can cause your grass to yellow, starting at the base. Although these two extremes can have a similar effect, here’s how to tell if your lawn is suffering from too much water:
- Does your lawn feel wet and soggy hours after watering? Is there an audible squish when you walk on it? These are signs of too much water.
- Is the grass turning yellow at the base rather than brown? Brown grass typically indicates drought and dormancy, while yellow coloration is caused by overwatering.
- An abundance of invasive weeds is a sign your lawn is receiving too much water. Crabgrass, chickweed, and many other weeds thrive in overwatered lawns.
In addition to these signs, providing your lawn with too much water increases thatch buildup by forcing accelerated grass growth and death. If you provide too much water, you’re creating the conditions for a lawn that is green on top and brown underneath.
Improper Soil pH
Soil that is too acidic, or not acidic enough, prevents grass from absorbing nutrients present in the soil. This results in struggling grass that is often brown below and pale green at the blade tips. To determine if this is the cause and remedy it:
- Grass grows best in soil with a pH of 5.8–7.0.
- Use a testing kit to determine your soil’s pH.
- If pH is outside the 5.8–7.0 range, add lime to reduce soil acidity, or use sulfur to increase acidity.
- Use humic acid to combat the negative effects of unbalanced pH, giving your grass a much-needed boost.
Cold Spring Weather
Your grass may be turning brown at the base due to spring cold snaps. Of course, this cause is entirely seasonal and you can rule it out in summer, but keep the following in mind.
- Is your grass experiencing green with brown beneath in spring? It could be due to a cold spring.
- Have there been recent nighttime frosts or temperatures nearing freezing?
- Some warm-season grasses, such as Bermuda grass, can begin to turn brown in temperatures as high as 55℉ (13℃).
Grass that has begun to green up as temperatures warm can be shocked by a single cold night. This can cause the grass to turn brown. It may take a week or more for grass to recover from this cold shock.
Why is Your Grass Brown Underneath?
Your grass could be brown near the roots but green on top for several reasons. These are an excessive buildup of thatch, a lack of fertilizer in the soil, improper watering, unbalanced soil pH, or simply because spring frosts are setting your grass back during green-up. It’s important to diagnose the cause and take steps to resolve it, so your lawn can be healthy and green again.
If your grass is green above and brown below, it’s likely not because of fungus, grass rust, or insects. These common grass maladies manifest as isolated brown spots and dead patches. This includes fungal and grub infestations. By eliminating the things you know aren’t harming your grass and testing the possible causes of grass discoloration, you can find a solution.