Analyzing Soil pH for a Healthy Garden (6 Easy Ways to Adjust Soil pH)

As a gardener, you know the importance of providing your plants with the best possible growing environment. One often overlooked aspect of this environment is the soil's pH level.

Soil pH is the measure of the soil's acidity or alkalinity on a scale of 0 to 14, with 7 being neutral, less than 7 is acidic, and greater than 7 is alkaline. Whatever the pH of your soil, you can adjust it in either direction with the addition of a few common soil amendments. 

Before you even think about planting, you’ll want to take a soil test to understand what the makeup of your soil is. Once you know your soil pH, you’ll know which plants will thrive in your native soil and how to adjust the soil pH to cater to different plants.

Keep reading to understand why soil pH is so important, how to adjust the pH of your garden, and which plants prefer different soil types!

Why soil pH is important

Soil pH directly affects plant health. Different plants require different soil pH levels for optimal growth, as soil pH determines nutrient availability. The chemical makeup of soil also affects the presence of microorganisms in the soil since most beneficial microbes prefer a slightly acidic to neutral soil pH of 6.0 to 7.0.

If a plant is exposed to an unfavorable pH for an extended period, it can also suffer from nutrient deficiencies. This may cause a reduced natural immunity, rendering the plant more susceptible to stress and disease.

Plants that prefer acidic soil, like azaleas and blueberries, will struggle to obtain nutrients in alkaline soil, leading to stunted growth and yellowing leaves. On the other hand, those that prefer alkaline-loving plants like lilacs and forsythia will struggle to grow to their full potential in acidic soil. By analyzing your soil's pH and making adjustments as needed, you can provide your plants with the optimal growing conditions they require.

How to test for soil pH

Testing your soil's pH level is easy with the right tools. The most common method is to use a soil pH test kit or meter, which will provide you with a digital or color-coded reading of your soil's pH level.

Alternatively, you can reach out to your closest Agricultural Extension office and send a soil sample to their lab. An official soil test will give you more detailed information about the specifics of your garden soil, including soil type, composition, and pH.

To take a soil test, all you need is a shovel and a container to put the sample in. When you take a sample, dig down at least six inches and transfer the soil to a plastic bag. Avoid getting grass or topsoil in the sample, as that may throw off the results. You’ll need to take a few soil samples from different areas of your garden to get an average of the entire area.

Adjust soil pH with these 6 amendments

Whatever the results of your soil test, there are certain amendments that can acidify the soil or make the soil more alkaline and bring the pH back to neutral. It's important to follow application rates carefully, as adding too much can cause further imbalances and harm your plants.

Amendments that acidify soil

If your soil is too alkaline, work sulfur or peat moss into the soil to increase acidity.

  1. Add compost

  2. Compost is the number-one soil amendment for so many reasons. First, compost adds essential nutrients and organic matter to the soil. Secondly, compost improves the texture and aeration of the soil. Finally, compost works to make alkaline soil more acidic.

  3. Add sulfur

  4. Soil experts recommend adding no more than three ounces of sulfur per square foot of soil. There are a few different kinds of sulfur—ferrous sulfate adds iron to the soil, and aluminum sulfate has been proven to work a little faster in the garden. Sulfur can be damaging to the soil if applied in large amounts, so always cut sulfur with compost to make it safer for your plants.

  5. Add peat moss

  6. Sphagnum peat moss is incredibly acidic, with a pH between 3.0 and 4.5. Peat moss also improves soil texture by increasing porosity and is totally safe for your garden. However, there are some environmental concerns about peat moss since it is currently mined from Canadian bogs at an unsustainable rate.

  7. Add wood chips or pine needles

  8. Mulching has a number of benefits: weed suppression, moisture retention, and, in the case of wood chips, it can even lower soil pH for acid-loving plants. Use aged wood chips whenever possible, and layer the wood chips on the surface of the soil—don’t till them in. 

    Pine needles tend to be a little more acidic than wood chips, making them an excellent choice for blueberries in particular. Whether you use wood chips or pine needles, source materials known to have not been treated with any chemicals. 

Amendments that make soil more alkaline

If your test indicates that your soil's pH is too acidic, you can adjust it by adding amendments like lime or wood ash.

  1. Add limestone

  2. Limestone is the go-to for reducing the acidity of garden soil. There are two types of limestone that may be used as soil amendments—calcitic and dolomitic lime. The only difference between the two types is that dolomitic lime contains significantly more magnesium than calcitic lime, but both types contain calcium and effectively raise soil pH.

  3. Add wood ash

According to an article by Olivia Saunders, the University of New Hampshire’s Extension Field Specialist, you might opt to use wood ash instead of limestone if you want to see quicker results. “Wood ash is more soluble and reactive than ground limestone, and
brings about a change in soil pH more quickly than lime,” Saunders writes. Wood ash also has several micronutrients that lime does not, including potassium, phosphorus, zinc, and copper.

Only apply the recommended soil amendments in the suggested amounts per your soil test results. It’s easy to over-apply soil amendments, and those damages can take time to remedy. When you handle any kind of soil amendment—no matter what it is—protect your hands with gardening gloves!

Soil pH preferences for different plants

The majority of landscaping plants prefer soil that is slightly acidic to neutral, but some plants favor soil that is more alkaline. We’ve broken down some of the most popular landscaping plants into categories based on soil pH below.

Plants that Prefer Acidic Soil:

Most of our favorite flowering shrubs and perennials thrive in soil that is slightly acidic.

Plants that prefer neutral soil pH:

Some plants prefer soil with a neutral pH but will tolerate slightly acidic or alkaline soil.

Plants that Prefer Alkaline Soil:

These plants prefer soil to be a little more alkaline than acidic.

Analyzing and adjusting soil pH may seem like a small task, but it can significantly affect your garden's health and productivity. By providing your plants with the optimal conditions they require, you'll be rewarded with beautiful gardens and landscapes. So make a note to get your soil tested, and follow the recommended guidelines to create an outdoor environment in which your favorite plants will thrive. 

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