If you’re wondering how to tell if your lawn needs lime, keep reading for our visual and soil tests. We also cover what causes soil to become acidic in the first place, and how to apply lime for the best effect.
Lawn lime is a soil amendment made from ground limestone rocks. These rocks are composed mainly of magnesium carbonate (MgCO3) and calcium carbonate (CaCO3).
Adding these compounds to your lawn raises the pH of the soil, making it less acidic. This increases the availability of essential nutrients and promotes overall lawn health.
Low soil pH can inhibit microbial activity and cause deficiencies in key nutrients like nitrogen, phosphorus and potassium. This ultimately leads to an unhealthy lawn that’s more susceptible to stresses like heat damage, droughts and weeds. Lime neutralizes acids in your soil and increases the pH. This has several benefits including:
Soil testing is the best and easiest way to understand if your lawn needs a lime application or not. There are also some more visual clues you can look out for, such as particular weeds growing in your grass.
Most of the physicals signs are general indicators of poor lawn health, so spotting one of these on their own doesn’t automatically mean your soil is too acidic. If your lawn displays several of the symptoms, or you live in a region with naturally acidic soil, then you can be more confident it’s suffering from a low pH.
Here are seven ways to tell if your lawn needs lime:
This is the most definitive way of understanding if your lawn would benefit from a lime application.
Doing a soil test will tell you the exact pH of your soil and therefore if it needs lime or not.
pH is a measure of how alkaline or acidic the soil is. 7 is neutral, below 7 is acidic and above 7 is alkaline. The ideal pH for your soil will vary depending on what type of grass you have, generally speaking it should be between 5.8-7 (slightly acidic). Cool-season grasses prefer to be at the lower end of the range, while warm-season grasses are happier at the higher end.
The ideal pH for most grasses is 6.5. Therefore, if the results show a pH of less than 6.5 your lawn would benefit from a lime application.
There are multiple different ways of testing your soil and we discuss these in more detail further on in the article.
One of the most obvious signs that the pH balance of your lawn is off is yellow grass that doesn’t seem to be growing.
Also, grass that’s having trouble bouncing back from drought or a heatwave is a telltale sign that your soil needs a lime treatment.
Because acidic lawns are deficient in nutrients, they struggle to recover from stress and can end up thin, patchy and dead looking.
Excessive weed growth is a sign of an unhealthy lawn. When grass is in a weakened state it’s easy for weeds to overtake.
Paying close attention to the type of weeds that are growing can give you an idea of the problem that’s causing them.
Here are some common weeds that may suggest your lawn needs lime:
All of the above weeds thrive in acidic soil. If you notice a few of these in your lawn then you can be pretty sure that your lawn needs lime.
The appearance of moss in your lawn is a visual clue that your grass isn’t getting the nutrients it needs. One thing we know inhibits nutrient uptake is a low pH.
Moss grows very well in acidic soil so is a good indication of high soil acidity.
If you find yourself having to add more and more fertilizer to see any sort of effect, then your lawn could be too acidic.
Acidic lawns can’t absorb nutrients. No matter how much nitrogen you throw at the grass, it’s not going to make a difference – this can sometimes even lead to people over-fertilizing.
If you live in the Eastern, Southern or Pacific Northwest region of the U.S then you’re soil will be naturally acidic, and is more likely to need a regular lime treatment.
These areas have higher rainfall and more acidic organic matter decaying. Both of these factors lead to increases in soil acidity.
Hydrangeas are excellent flowers to grow if you want a visual indicator of the pH of your soil.
The flowers change colour depending on the pH of the soil they’re grown in. They’ll turn pink in acidic soil and blue in basic soil.
As we explained earlier, the most reliable way to answer the question ‘how to tell if your lawn needs lime’ is to do a soil test. If the pH level is lower than 6.5 then your lawn could benefit from applying lime.
There are three different ways to conduct a soil test:
Sending off a sample of your soil will give you the most accurate results. The results will also inform you exactly how much lime you need to apply, as well as what type of soil you have and any additional amendments you need.
Using a home soil test kit is the simplest option. You can either use strips or a pH meter. Both of these can be purchased online. The results from these tests are instant and will tell you the pH of the soil, but not how much lime you need to add.
A DIY test is cheap and easy to conduct. But the results only give you an indication of the pH level of your soil, not an exact measurement.
We conducted the test on our soil at home, and have posted the results below each step.
Step 1: Split your soil sample between the two containers
Here’s a picture of the equipment we used. We used red wine vinegar but any vinegar you have at home will work.
Step 2: Add the vinegar to one of the soil samples. If it sizzles your soil has a basic pH level (alkaline).
In our test, there was no reaction between the soil and the vinegar – so we don’t have basic soil.
Step 3: Add the water to the other cup until the soil is mud-like in texture
Step 4: Add the baking soda, if the mixture sizzles your soil has an acidic pH level and it needs a lime treatment
Our solution started fizzing and bubbling when we added the baking soda indicating that we have acidic soil.
Step 5: If neither solution reacts your soil is neutral
An acidic lawn might be the norm where you live, or outside influences could have upset the pH balance in your soil. Understanding what can cause your lawn to become too acidic can also help you with understanding how to tell if your lawn needs lime.
Here are five things that can contribute to creating an acidic soil environment.
Sandy soil is bad at holding nutrients. Basic elements like calcium are easily washed away leaving acidic soil in their wake.
Sandy soils need lime applications little and often. The porous nature of the soil means a small amount of lime can quickly raise the pH level, but the lime is swiftly leached away and needs to be reapplied.
Clay soil is stickier and requires much more lime to balance an acidic pH. But once the pH of clay soil has reached neutral, it’ll stay like that for much longer.
Ammonium based nitrogen fertilizers release acidic hydrogen cations into the soil as they work. Over time this lowers the soil pH until eventually, it’s so low it needs a lime treatment.
If you live somewhere with naturally acidic soil, you can reduce how often you have to lime your lawn by using organic fertilizers. Urea and compost are less acidifying than ammonium-based fertilizers.
One of the reasons Eastern, Southern and Pacific Northwest regions have naturally acidic soil is because they experience high levels of rainfall.
Both rain and excessive irrigation will increase the rate at which alkaline elements like potassium and calcium leach out of the soil. This, in turn, creates a more acidic environment.
If you live in an area that experiences acid rain then it’s almost a certainty that you need to apply lime to your lawn.
Eastern, Southern and Pacific Northwest regions also tend to have more trees. Leaves and pine needles are acidic in nature. As they decay, they cause the surrounding soil acidity to increase.
Even if you don’t water excessively and use compost as fertilizer, a healthy lawn will still gradually acidify the soil.
Healthy grass will use alkaline nutrients from the soil to grow, eventually depleting them to low enough levels that you need to apply lime. The increased microbial activity associated with good lawn care will also gradually create a more acidic environment.
Spring or fall is the best time to apply lime, although you can apply it any time of year as long as the ground isn’t frozen.
Fall is preferred by most gardeners because this coincides with the overseeding season. The increased rainfall over winter and the cycles of freezing and thawing helps the lime to breakdown and penetrate deep into your soil.
Lime shouldn’t be applied to an overly wet or dry lawn. Wait for a period of dry, cool weather and water your lawn to moisten the soil just before applying the lime.
To give your lime the best chance of working it’s best to apply it after you’ve aerated the lawn. Aeration enables the lime to reach deeper into your soil, where it’ll be more effective than if you just spread it on the surface.
The quickest way to spread the lime is to use a standard garden spreader. We like Scotts broadcast spreader because it’s easy to use and has multiple use cases.
After you’ve applied the lime, water it down to ensure it’s well incorporated into the soil and not just stuck to the grass.
Lime can take a few months to work, and if your soil had a really low pH then you might need a few applications of lime before the imbalance is corrected.
We recommend testing your lawn every year to check the pH levels. For most lawns, after the initial lime treatment, an application every 3 years will be sufficient.
There are broadly two types of lime you can buy for your lawn. These are dolomitic lime and calcitic lime.
Dolomitic lime, also sometimes referred to simply as ‘dolomite lime’ contains both magnesium and calcium. Its use is recommended when your soil is deficient in magnesium as well as suffering from a low pH.
Calcitic lime is derived from deposits that contain mostly calcium carbonate. It lacks the magnesium found in dolomitic lime. If your soil test shows that your soil is not deficient in magnesium then you should use calcitic lime.
Lime today is sold in different forms, including:
We use Penningtons fast-acting lime for our lawn.
It comes in a pelletized form so is easily applied using a lawn spreader, and you get noticeably faster results.
The pellets combine advanced soil technology with high-quality dolomitic lime to maximize the benefits to your lawn.
Giving your lawn a lime treatment will help keep it looking thick and green all year round.
Have you had success liming your lawn? Do you have any more tips for how to tell if your lawn needs lime? Let us know.
Make sure to check out the rest of our website for more awesome lawn care tips.
Veronica has a passion for all things eco-friendly. After growing up on a farm in Ireland, she went on to study Chemistry and Environmental Sciences. Veronica has also volunteered in many sustainability roles, including conservation efforts in Bangladesh and teaching Environmental Sciences to schoolchildren in Kenya.