BROWN GRASS: Soil Too Acidic?

Brown Grass in just a portion of your lawn may result from one of these conditions:

  • A watering problem 
  • Extreme climate change (local, not the global kind!)
  • The amount of shade
  • Insect or disease problems 

Understand how these situations develop into problems and what to do about them, in this entry from our Question & Answer series.

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A Reader's QUESTION: 

The lawn is turning brown under evergreens in my yard. Is the brown grass due to acidic soil?

Garden Counselor ANSWER:

It is true that evergreens tend to make the soil beneath them more acidic. This could contribute to your grass turning brown over a period of time. There are other factors to consider, but we won’t rule out this possibility. Extremely acidic soil would be a poor growing environment for a lawn.

It is always a good idea to know the quality of your soil for a lawn or garden area, so you might consider getting an inexpensive pH tester to check it. Quick pH meters are available for about $15, or simple pH test kits for about half that amount.

However, I would first suspect that the brown grass is caused by other problems. Consider all these possibilities, because any of them can occur quite quickly, or over a long period of time, depending on the degree of the circumstances involved.

1. A watering problem
is the first condition I always want to investigate and eliminate or correct. Even when I say it is a priority, the majority of people assume it's fine and don't give it a second thought. Don’t make that mistake.
In many parts of the country, it should be your first thought, even if you have an irrigation system and use it. Honestly, this is a bigger issue than most people imagine, and it is simple to check.

Please go to several spots in the lawn area and dig up a shovelful of grass and dirt as deep as the shovel will go. Do this where you see brown grass, but also where the grass is still green and where it may be showing a rather in-between condition. When you are done looking at it, you’ll put it right back as it came out, so this process typically harms nothing.

Compare soil in the brown grass area with a spot from an area where the lawn is doing better and see if the moisture amount is different. Is the soil moist as you look at 2", 4'', & 6" of depth? Is it consistently moist all the way through?
If the soil is not moist enough that it will crumble if you poke at it (or is too hard to get the shovel all the way down), then the lawn simply needs to be irrigated.

If more water is indicated, this could reflect a deficiency in your irrigation system if you have one, or insufficient length or frequency of watering if you do it manually. It could also mean that the evergreens are too competitive for the amount of water available, and are sucking it up to the detriment of the grass in the area of that root zone.

2. Extreme climate change
is another factor to consider. It can happen that a particular area in a lawn is affected by environmental conditions more than the rest of the grass. A hot spell or a lengthy period of windy days can cause available water in the soil to be inadequate to match the higher evaporation rate from the grass.

It only takes a temporary stress to convert grass that is existing in a marginal healthy state into an ongoing problem, when conditions are not conducive to recovery/improvement. 

Whether or not this results in brown grass, or how quickly it happens, will depend on how healthy the grass is, how strong the grass roots are and how deep they go, and the available moisture available in the root zone area.

3. The amount of shade
that the evergreens might be casting on the lawn is a third concern. Shade will typically cause a lawn to fail to thrive, and it will thin out over a period of time. However, without knowing the type of evergreens or their size and density, nor the age of your lawn, new or old, and type of grass, it is something to consider.

Sometimes this may not seem likely, since last year you didn’t really notice a problem with the grass turning brown, for example. However, shade often increases over time, and it can be a contributing factor that often acts in tandem with other environmental stresses. Finally they all come together in sort of a landscaper’s version of the perfect storm.

4. Insect or disease problems
potentially could exist in the area near your evergreens, but not in the entire lawn area. This could especially occur if you have the opposite watering problem, too much moisture.

If the area under the evergreens is constantly damp, and the rest of the lawn is not, that can be conducive to a very selective growing problem. Diseases thrive in constant moisture, and grass roots need oxygen which can be scarce if water is too plentiful.
A brown lawn that is sporadic can result.


If none of these elements seem to be contributing to the problem, a treatment for acidic soil could be the answer. It would be advisable to check the pH of the soil.
Most lawn grasses do well in the range of 6.0 - 7.0, which is slightly acidic. If the soil in the area where you have the brown grass is below 6.0, you can apply agricultural lime to bring the pH up to a better level.

If low moisture seems to be a factor, strive to adjust your lawn watering routine so that the water is able to deeply penetrate the soil. This typically means watering for a longer period of time, but doing it less frequently, so that the grass roots are encouraged to grow deep toward the moisture.

If the soil is hard packed, it may not absorb the extra water without running off. In this case, it would help to aerate the top layer of soil, and apply a short period of watering (until it starts to run off), a short break, then more watering for a short interval. Repeat that cycle a number of times, all in one day, until the water penetrates.

You can also apply products that help the water penetrate the soil, and these are very effective at improving water absorption. Examples of these: Soil Logic's Liquid Gypsum which not only enhances drainage, but furnishes the important trace mineral, calcium, to improve the soil quality; also, Grow More E-Z Wet Soil Penetrant is inexpensive and can be applied through a hose end sprayer.

These are available direct from these online sources:

SoilLogic's Liquid "Gypsum"
Grow More E-Z Wet Soil Penetrant 26

As a final thought, if nothing else seems to apply, pay attention to any differences in how various areas of your lawn are utilized.

Do you have extra traffic in that certain area from people or equipment; dogs constantly laying on the grass or urinating there; or things being dumped out on the lawn? (In one case, soapy water from washing was the culprit.)

Things like that could be precipitating factors that lead to brown grass. Just observe and think it through.


Go To Why Grass Stays Brown

Go To Brown Grass: Questions & Answers

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