I’m pretty sure we are all aiming for a lush green lawn, and we try to avoid any brown areas as much as possible. But unfortunately, this can be a challenging task. If you dig down into your lawn and find the grass is green on top and brown underneath, then there could be something going on that needs your attention. So, let’s take a closer look at your lawn and determine what action you should take.
Why is My Grass Brown Underneath the Surface? (The Short Answer)
Grass needs a particular set of parameters to thrive. Therefore, anytime these parameters are not met, you may find that your grass is green on top and brown underneath. In addition, you might find that browning is just part of your lawn’s natural process. Here are six common causes for brown grass underneath green grass.
- Dormant Grass & Cold Weather
- Thatch Build Up
- Lack of Nutrients
- pH Imbalance
- Underwatering
- Overwatering
6 Possible Reasons for Brown Grass Underneath Green Grass
Brown grass underneath green grass is a common symptom of a lawn that isn’t efficiently growing. Several different factors can cause this. Here’s what you can check to find out why your lawn is brown underneath.
Dormant Grass & Cold Weather
Before you dig too deep into why your grass is green on top and brown underneath, you want to take note of the weather. If you’re in winter or early spring, your lawn may be reacting to the cold temperature. Similarly, your lawn may turn brown underneath if you are experiencing a hot summer. Again, this is just your lawn reacting to the weather and preserving energy, water, and nutrients. So if you can rule out the weather as a contributing factor, you’ll need to look for additional causes.
Thatch Build Up
Thatch is a pretty common reason your lawn will look brown underneath and green on top. It’s not a case that there is a problem with the actual living and growing grass; it’s just that the thatch is dead and brown.
So, you could be looking at thatch and not your actual lawn. But, if the layer of thatch is too thick, your grass may suffer. A thick layer of thatch can block air, water, and nutrients from reaching the soil and roots.
Also, thatch will eventually decompose into compost and make up the top layer of soil. The top layer is an organic/humus soil layer and shouldn’t be too thick. This is because the grass roots can’t grow solely in compost. So, if there is too much compost from thatch, the grass may slowly die as the small new roots can’t reach the topsoil.
Lack of Nutrients
Grass green on top and brown underneath is a common sign that your lawn might not be receiving the correct nutrients throughout the year. The side effect is that your grass blades may turn brown, first at the bottom and then at the blade tips.
Here are a few examples of the levels of nitrogen that grass types should receive throughout the year.
Annual Nitrogen Application Quantities
- Augustine 2-4 lb/1000 ft2/year
- Zoysia 2-4 lb/1000 ft2/year
- Bermuda 2-4 lb/1000 ft2/year
- Tall Fescue 3-5 lb/1000 ft2/year
- Bluegrass 3-5 lb/1000 ft2/year
pH Imbalance
Soil amending is generally focused on increasing the nutrient value to increase the food for the lawn. But unfortunately, this neglects the ph level of the soil. Actually, what happens when you add nitrogen-based fertilizers to a lawn is that the nitrogen reduces the ph and increases the soil’s acidity.
For example, if your ideal soil pH is 6, then nitrogen fertilizer will slowly reduce this number closer to 0 on the pH scale, making the soil more acidic. The result is your lawn will turn brown from a pH imbalance. Soil that is too alkaline is also a problem and will turn your grass brown underneath. However, rainwater, clippings, and grass thatch naturally lower the pH to acceptable levels, so you rarely need to worry about alkalinity levels.
Here are some examples of ideal pH levels for different grass types.
Idea pH Level of Lawn Grasses
- Augustine 6-6.5
- Zoysia 6-6.5
- Bermuda 6-6.5
- Tall Fescue 5-7.5
- Bluegrass 5-8.5
Underwatering & Overwatering Your Lawn
Next on the list is underwatering and overwatering your lawn. Grass uses water at the roots to absorb nutrients and minerals through the plant to produce sugars and carbohydrates, creating cell division or growth, development, and reproduction. So, with too little water, your grass isn’t going to grow, and it will likely turn brown.
At the opposite end of the scale is too much water. So, even though water is a vital ingredient for grass to grow, too much can be a problem. This is because, as well as needing water, grass roots also need to absorb oxygen. Too much water will suffocate the roots and prevent oxygen from reaching the roots for absorption. If this happens, you’ll see the underneath of your lawn turn brown, and the tops stay green.
Also, if this process is allowed to continue for too long, then the top of the grass will also turn brown.
What to Do If Your Grass is Green On Top and Brown Underneath (4 Things to Try)
Now that we have answered why my grass is brown underneath, let’s take a look at some solutions. Here are 4 things to try if your lawn is green on top and brown underneath.
Dethatch the Lawn
The easiest way to get rid of thatch in a lawn is to use a lawn dethatcher. These are walk-behind pieces of equipment that look pretty much like lawn mowers. The difference is that a dethatcher combs the grass without cutting. Now, you could use a garden rake, but mechanical dethatchers actually do a much better job in a much quicker time.
So, when should you dethatch? Well, most people dethatch in the spring and fall. However, you can detach any time you like, as long as you remove the thatch throughout the year. Just avoid dethatching during the hottest parts of summer and winter.
Tools to Dethatch a Lawn
- Dethatch Rake or Mechanical Dethatcher
Fertilize the Lawn
The days of having to send away a sample of dirt and wait for a lab to test your soil are a thing of the past. Of course, you can still use a laboratory facility, but now you can test your nitrogen (N), phosphorus (P), and potassium (K) levels right in your backyard. Simple homeowner test kits like the Rapitest give you the ability to test your NPK levels so you know exactly what your lawn requires.
Once you have your results, you’ll have a pretty good idea of what your lawn needs, making selecting a fertilizer product easy. Then, all that’s left to do is spread your fertilizer with a drop spreader, broadcast spreader, or handheld spreader. Make sure you follow your local city ordinance for application limits and blackout dates.
If your lawn needs a quick boost, I recommend using liquid fertilizer. Then to give your lawn a long slow continuous feed, I recommend using a slow-release granular fertilizer every couple of months.
Tools & Materials for Soil Testing & Fertilizing
- Test Kit
- Fertilizer Spreader
- Fertilizer
Adjust the Soil pH
A few different options are available to test your soil’s pH, ranging from sending off a soil sample to using a test kit. However, my preferred method is to use a soil pH meter, a small device with two probes that you press down into the ground to get an instant pH reading. As long as you follow the instructions, this process should only take a few seconds.
So, what do you do when you have the results? Well, you amend the soil with a product such as lime. If you already have a fertilizer spreader, then all you’ll need to do is grab a bag of lime such as Sta-Green fast-acting lime. Then use the results of your test along with the application rate stated on the product, and off you go. Spread the lime just the same as if you were spreading fertilizer.
Tools & Materials to Adjust Soil pH
- pH Soil Meter
- Fertilizer Spreader
- Granular Lawn Lime
Adjust the Soil Moisture Content
Last on the list of solutions for brown grass underneath green grass is to adjust your watering schedule. You could poke your finger into the soil and try to work out what is going on, but unless you have some pretty long fingers, this isn’t really going to work. So, what’s the second option? You can get your hands on another piece of equipment to test the soil’s moisture.
A soil moisture meter, just like the pH meter, is a small, inexpensive tool with two probes that you spike into the ground. However, this time, you get a moisture reading. Now, you can pick up a tester that can test both pH and moisture at no extra cost.
So, all you need to do is spike the meter into the ground and check if your lawn is wet, dry, or just right. Depending on the results, you’ll need to either increase or decrease the period you water your lawn. The best way to dial in my irrigation is to test the soil each day between watering cycles and note down the reading on the meter. Then if I discover my lawn is drying out, I increase the water period if possible.
Now if my lawn stays on the too-moist side of the meter, I reduce the watering time. So, to dial in my irrigation, I’d only make small adjustments, say +/- 10 minutes at a time. After a couple of cycles, your soil moisture should be right about perfect most of the time.
Tools to Test Soil Moisture Content
- Soil Moisture Content Meter
Leave a Reply