The importance of ph level in soil (how to test & fix it)

Plant care is important. But what about the pH level of soil?

We spend time on potting mixes, nutrients and watering correctly. Do we rally need to care about the pH level of soil?

The PH level of your soil is important. If we do not get it right our plants will not thrive and we will be scratching our heads wondering why.

This article will explain what pH is and why we need to care. We will also explain why you do not need to worry excessively about it if your plants are doing well.

I will give you an easy method to indicate whether your soil is acidic, neutral or alkaline.

And then finally, I will tell you how you can measure the pH level in soil for a one time investment of less than $10.

What does ph measure?

The pH level in soil indicates whether your soil is acidic, neutral or alkaline. 

Soil with a pH below 7 is acidic, pH measuring 7.0 is neutral and a soil with a pH above 7 is considered alkaline.

Why do we care about ph levels?

The good news is that most garden herbs and vegetables do well at a slightly acidic to neutral pH level. The range that is commonly cited is pH 5,5 – 7,5.

But as a garden enthusiast you do not need to worry about pH levels if your plants are doing well.

But if you are experiencing yellow leaves or limp and lifeless plants you may have a problem with a soil that is too acidic or alkaline.

What happens when we get the ph level wrong?

Most plants are resilient and will tolerate pH levels that are slightly off. 

But when the soil mix gets too acidic or alkaline you will no longer have healthy and thriving plants. 

The wrong pH level will bind nutrients that are necessary for the plant to grow and leave the plant underfed and struggling.

Without going into too much detail you should know that different types of nutrients become unavailable to the plants at different levels of pH. 

This is why we strive for a slightly acidic to neutral soil for most of our herbs and vegetables.

How to test if soil is acidic, neutral or alkaline?

There are many ways to test the pH level of your soil. 

You can buy a measuring stick, use a pH strip or even send soil samples to a laboratory for analysis.

I use a Soil pH Meter as well as a trick my mother taught me.

Testing the pH level of soil using a Soil pH Meter

Soil pH Meters read soil pH levels for all types of soil

To take a pH reading of you soil you simply push the probe into moist soil and wait for 60 seconds.

A reading of 7 indicates Neutral. Between 3-7 is acidic and between 7-10 indicates alkaline.

It is important that the soil is moist and to insert the probe about 5 inches (12 cm) deep. You should take 2-3 reading in different places as the pH level can differ even in smaller pots.

You can buy a Soil pH Meter reader for less than $10 online and it is a very useful item to own.

Testing The PH Level Of Your Soil using my mother’s method

I also use a tried and tested method my mother taught me. And when I say my Mother’s method I am not implying that she invested the method. But she did tell me about it.

Many years ago, when I was still living with my parents, we used lime treated horse manure to feed our tomato plants.  

We added a bit too much and the plants did not react well. It turned out that we had increased the pH level dramatically. (We may also have burnt the roots but that is a different article.)

We had to dig out the soil and spent almost a full season getting everything back to normal.

This is the method my mother taught me.

1. Preparation and items needed

To test the ph level of your soil you need 2 glass jars, distilled water, vinegar and baking soda.

This test will indicate whether your soil is acidic, neutral or alkaline. You will however not receive a firm value. But most of the time we do not need a firm value. 

This is also why we do not use tap water (slightly alkaline) or rain water (slightly acidic) for our tests.

You only need a small sample of soil to perform the test. A couple of tablespoons of soil will work just fine. 

The soil is not alkaline
No bubbles after adding vinegar. The soil is not alkaline.

2. Testing for alkaline soil

  1. Place two tablespoons of the soil sample you are testing in one of the glass jars.
  2. Add 2 tablespoons of vinegar and stir vigorously.

Conclusion: If the soil starts to bubble or fizz your soil is alkaline.

If there is no reaction your soil is neutral or acidic and we move on to step 2. 

3. Testing for acidic soil

  1. Place two tablespoons of the soil sample you are testing in the other glass jar.
  2. Add 2 tablespoons of distilled water and stir soil into a muddy mixture
  3. Now add 2 tablespoons of baking soda and stir vigorously

Conclusion: If the soil mixture starts to bubble or fizz your soil is acidic.

If there is still no reaction, your soil is neutral.

How can we alter the pH level of our soil?

To alter the pH level of soil is not difficult but can take time for larger areas.

Vegetable gardens

If your soil is too acidic you need to add lime to your soil. The lime will over time make your soil more alkaline but do not expect the change to occur instantly.

Should your soil be too alkaline I recommend adding peat moss that will help lower the pH and make the soil more acidic over time. A quicker fix is using aluminum sulfate or elemental sulfur that can be sourced from most well stocked garden centers.

Pots and containers

If you have a problem with pH levels in pots or containers I suggest replacing the soil altogether.

Whether the soil is too acidic or alkaline you can still reuse it. Simply mix the soil with other soil and add lime or peat moss as needed.

It is however easier to start with a fresh pot of soil. Either way you will need to disturb the root system and a fresh soil mix should give the plant a better chance to recover.

When to worry about ph levels

I rarely test my soil. And I even have a Soil pH Meter.

My advice is not to worry about pH levels if your plants are doing well. Your plants will tell you if there is a problem.

And even when there is a problem with your plants there is no need to suspect pH levels to be the cause. At least not initially. 

Your first step should always be to look through your gardening journal to see if there is another explanation. Especially if you have plants in containers, garden beds or pots with fresh soil mixes.

10 questions to ask before worrying about pH levels

With every bit of new knowledge it is easy to lose sight of the fundamentals. And we can most of the time find the answers to why our plants are struggling from the following questions.

1. Are you watering your plants too much?
2. Have your plants suffered dry outs due to lack of water?
3. Are you giving your plants enough sunlight?
4. Have you exposed your plants to too much direct sunlight?
5. Is your soil well drained?
6. When was the last time you added nutrients or fertilizers?
7. Are you using the correct size pot?
8. Have you planted too many seedlings in the same pot (overcrowding)?
9. Did you move the pots outdoors or change the growing environment?
10. Has there been a substantial change in temperature, wind or precipitation?

This is by no means a complete list. My point is simply that there are many factors that can affect the wellbeing of our herbs and plants.

Jumping to pH level problems may not be necessary before we ensure that we are in fact managing to meet the plant’s basic needs.

Are we in fact giving the plant enough light, water, nutrients, oxygen as well as a well drained soil structure to develop and anchor its root system?

When I want to know the ph level of soil

Garden enthusiasts and experts alike want to provide plants with the best possible growing environment.

So it is of course great if we are mindful of the pH level of our soil.

I know that most herbs and vegetables like a slightly acidic to neutral soil in the pH range of 5,5 – 7,5. You can find pH information on most seed packets.

Thyme, basil, parsley, sage and rosemary benefit from soil in the lower part of this range whereas for example peppermint and spinach prefer a value closer to pH 7,5. 

But there are times when I do want to know the correct pH level. And this is how I do it when I am being my most pedantic self. 

And no, I do not always do this. But I do like to check the pH level when I plant a herb or vegetable for the first time. Or if I am planting in a location where I have never planted a particular herb or vegetable before. You know, when I test and try something completely new.

Checking the ph level when trying something new

Let’s say I wanted to grow arugula and that I had never grown arugula in my planting boxes before.

I know that arugula prefers a pH between 6-7. This means a slightly acidic to neutral soil.

Here I would test the soil in my planting boxes to make sure that the pH level is in a favourable range. I would not worry about small deviations but would keep the overall range of pH 6-7 in mind.

If it was far off I would make sure to get the value right before planting.

So yes, pH levels do matter and we should pay attention to them when we can.

Ensuring the correct ph level when mixing your own soil

The same principle applies when I mix my own potting soil. I have made sure that my soil mixes give me a slightly acidic potting soil mix when using my two different soil recipes. 

I say my recipes. They are most likely not unique. I just call them mine as I have arrived at the quantities through trial and error.

Frequently asked questions

Meet the author: Mattias is an experienced gardener spending most of his free time on his knees among herbs, plants and garden vegetables. For the past two years he has been sharing gardening projects and how-to tutorials on the NordicLavender website and YouTube channel.