Effects of Acidic Soil and How to Manage It for Healthy Plants

Acidic soil has a pH lower than 6.5 (a reading of 5.5 signifies that the soil is extremely acidic). The optimal pH range for the majority of species is 7, which is neutral. Readings above 7 or 7.5 indicate alkalinity.

Acidic soil can be beneficial for your garden when plants thrive in it. It promotes the growth of healthy microbes and bacteria and provides a healthy habitat for earthworms and other beneficial organisms. 

In addition, acidic soils are commonly described as “sour” and tend to be deficient in minerals, which could impact plant growth.

Learn more about acidic soils, their implications for your plants, and how to improve the soil to benefit your plants if needed.

Effects of Acidic Soil

Acidic soils can adversely alter the soil’s structure and, consequently, the health of plants. Excess acidity can reduce the availability of nutrients to roots, leading to magnesium, calcium, and potassium deficiencies. 

Toxic elements, such as manganese and aluminum, can affect the plant’s health more in acidic conditions. Additionally, acidic soils could hinder beneficial organisms from recycling vital nutrients like nitrogen.

How to Make Soil More Acidic

There are numerous ways to lower the pH of your soil. One method is to put down organic mulch rich in acidity, such as pine needles or oak leaves. 

As they decay, they’ll boost the pH of the soil underneath. Another option is to add soil amendments, such as sulfur or iron. Sulfur, however, may take a long time to show effects, while iron sulfate is used in large and cumbersome quantities. 

Sphagnum peat moss may lower the soil’s pH while providing essential organic matter to the soil. It’s a non-renewable resource, but it is considered unsustainable. Ammonium-based fertilizers are a great choice, as they break down and change to nitrate, increasing the soil’s acidity. 

Composting is a good alternative, particularly when made of acid-rich materials like coffee grounds, tree leaves, needles, or crushed Christmas trees. Compost is most effective when blended with coarse material such as perlite, sand, or acid-rich topsoil.

What Causes Acidic Soil?

Three factors can indeed cause soil acidity:

• The primary and most commonly cited factor is the breakdown of soil organic matter and minerals over time, which causes soil to become acidic. This is a common occurrence in peat bogs and pine forests.
• Another way soil becomes acidic is through excessive irrigation or rainfall. Excess water leaches essential nutrients from the soil, including magnesium, potassium, and calcium. These elements prevent the soil from becoming acidic, so when they are leached out, the soil’s pH level begins to decrease, resulting in more acidic soil.
• The third reason soil becomes acidic is through the application of synthetic fertilizers with high levels of nitrogen. These fertilizers typically contain ammonia, which increases soil acidity.

Types of Flowers That Thrive in Acidic Soil

What do you know about which plants to choose for your acidic soil?

Soil in wet areas tends to be more acidic than soil in drier areas; however, most flowering plants prefer low pH levels, which determine soil acidity or alkalinity. The lower the pH, the more acidic the soil. Generally, soil with a pH of 4.6 or lower is considered too acidic to support most plants.

Here is a helpful list of flowers that thrive in extremely acidic soils:

Hydrangeas

These plants are found throughout U.S. Department of Agriculture zones 4 to 9. Hydrangeas are small to medium-sized bushes that produce large flower clusters of smaller blooms. The most sought-after shades of this flower are white, pink, and blue. The soil pH must remain between 4.5 and 5.5 to grow blue blooms. These plants thrive in shade and humid soil.

Camellias

Camellias thrive best in shaded regions with well-drained soil in zones 6 to 9, depending on the type of camellia. They thrive in mildly acidic soils with a pH ranging from 5.0 to 6.0 and are evergreen climbers of medium size that bloom in spring.

Foxgloves

Foxgloves are perennial and biennial plants with small flowers that form a “tubelike” shape and open on the stem. 

They are available in a variety of shades, including purple, pink, white, and yellow. They bloom in late spring and summer and are most successful in shaded areas of USDA zones 3 to 8. Foxgloves prefer slightly acidic soil with a pH as high as 5.5.

Rhododendrons and Azaleas

Rhododendrons and Azaleas bloom in small to medium-sized plants, typically with pink or white flowers, although other colors are also available. These two species thrive in acidic soils, with a pH range between 4.5 and 6.0, and perform best when planted in USDA zones 3 to 9, depending on the variety.

Zinnias

Zinnias are tiny, vibrant flowers that resemble marigolds. They bloom in the summer and are adaptable. They can be found in most areas of the United States in USDA zones 3-10. These plants flourish in soils with acidity, with pH levels in the range of 5.5.

Bleeding Hearts

The Bleeding Heart plant is a unique ornamental plant with white and pink flowers designed like hearts hanging from the stems. The plant thrives in USDA zones 3 to 9 and is most successful in partial sun. It grows best in moderately acidic soils with a pH range from 5.0 to 6.5.

How to Test Your Soil

Verify the pH of your soil every couple of years. Is it possible to send a soil sample to a local extension office for testing, or can you perform the test yourself? 

Test kits are readily available at retail stores, home improvement, and garden centers. Find out the pH preferences of your plants. It’s essential to research your plants before planting them to find out which species prefer soils that are either acidic or alkaline.

Reasons to Make Soil More Acidic

Why should you discover ways to lower the pH of your soil? Every plant has a pH range it prefers. This range allows it to absorb all the nutrients required for growth. If the pH exceeds the preferred range, the plant will be affected and may even die.

As mentioned earlier, the uptake of nutrients in certain plants is affected by pH. Iron deficiency occurs because the soil pH is too high for plants. 

When plants aren’t receiving enough iron, the root cause is a soil pH that is too high. Even if the soil pH is less than 7.0, it may still not be enough for certain plants to absorb enough iron.

How to Make Soil More or Less Acidic

Soil can be altered to become more or less acidic. It’s crucial to monitor the pH of your soil regularly since it takes time for levels to shift.

• Raising Soil Acidity

You can increase soil acidity to satisfy plants that need acidity (often known as “acid-loving” plants). This will lower the pH of your soil. The best way to raise acidity is to utilize commercial fertilizers containing ammonium-N. This ingredient is commonly found in fertilizers designed for specific plants.

• Lowering Soil Acidity

However, plants that prefer sweet soils may struggle in acidic soils. Gardening lime, a white, powdery substance often spread across agricultural land, can reduce the soil’s acidity by increasing the pH. Lime has been used for years to sweeten soils with acidic pH.

If soil tests indicate that the pH needs to be raised, you can apply garden lime to your autumn garden and lawn care routine. The effects will become evident during the next growing season.

FAQ

How can I make my soil more acidic?

Wood chips, ericaceous compost, leaf mold, and well-rotted manure can aid in this process by naturally decreasing the soil’s pH over time. If you have access to oak leaves, pine needles, or coffee grounds, spread them around the ericaceous plants, as they can quickly boost acidity.

What are the symptoms of soil acidity?

Stunted grass growth, with wilting blades, yellow spots, or yellow patches on the lawn.

What are the indicators of acidic soil?

• Weed infestations—dandelions, knotweed, horsetail, and sorrel flourish in acidic soils.
• A high volume of oak and pine trees or moss thrive in acidic soil.
• Clay or sandy soil.

Which fertilizer improves the soil’s acidity?

Nitrogen fertilizers

Ammonium is a nitrogen source in manures, fertilizers, and legumes. Unless the plant absorbs the ammonium particles, the soil acidifies. The higher the rate of nitrogen fertilization, the higher the acidification of the soil.

Is acidic soil good or bad?

Acidity can impact soil in the following ways: It lowers the availability of plant nutrients like phosphorus and molybdenum. It also increases the accessibility of certain elements at toxic levels, such as manganese and aluminum. Essential plant nutrients can be released under the rooting zones.