Acidic Potting Soil – Everything You Need To Know

Acidic Potting Soil - Everything You Need To Know

Last Updated on July 6, 2022

Potting soil has many benefits for your plants, such as that it retains moisture and contains more nutrients than what you’ll find in garden soil.

However, you need to ensure that your potting soil has the correct pH so that it can accommodate the growth of various plants. This should generally be between 6.0 and 7.0 pH, as most plants will thrive in such soil conditions.

Is potting soil usually acidic? Generally, potting soil tends to be a bit acidic in nature, as a result of how it’s filled with a balance of nutrients for plants.

However, you can raise or lower the soil pH so that you give your specific plants what they need to grow. With this in mind, let’s explore acidic potting soil and how to make it work for your plants.

We’ll start by featuring some common plants that love acidic soil. 

What Are Acid Loving Plants? 

What Are Acid Loving Plants? 

Some plants want their soil to have acidic pH, which is lower than 6.0 pH. These include the following:

  • Some berries. Berries that love acidic soil include blueberries, thimbleberries, cranberries, and gooseberries. They all thrive in soil conditions that have a very low pH of between 4.0 and 5.0.
  • Some vegetables. Veggies such as cucumbers and sweet corn do well when they’re planted in soil between 5.5 to 7.5 pH. Other vegetables, such as turnips, beans, and tomatoes, require soil that has a pH of between 5.5 and 7.0. 
  • Azaleas. If you plant azaleas in soil that’s not acidic, they will battle to grow or their leaves can turn yellow. These plants require 4.5 to 6 pH soil. 
  • Hydrangeas. These pink, white, or blue flowering plants like soil that’s acidic, with a pH of 5.2 to 5.5, although they are able to tolerate neutral soil that has a pH of 7. This makes them quite versatile to plant in the garden. 
  • Magnolia. This pink flowering plant grows well in moist, well-draining soil that has a neutral-to-acidic soil pH. Ideally, it does best when planted in acidic soil.
  • Bayberry. This shrub prefers sandy, moist, and slightly acidic soil. If grown in alkaline soil, it will experience chlorosis, which is when plant leaves become yellow as a result of a lack of chlorophyll. If you’re growing bayberry at home, make sure that its soil has a pH of between 5.6 to 6.5.

Is Potting Soil Acidic?

Is Potting Soil Acidic?

Potting soil, which is used to nourish potted plants and plants in containers, is usually a bit acidic in nature, with a pH of around 6.0 to 7.0. This is a general pH that most types of plants prefer to be planted in, so it’s not harmful to your plants.   

Still, it’s good to check the potting soil bag for information about that specific potting soil. If you have acid-loving plants in your home, you’ll want to check that the potting soil bag is designed for acid-loving plants. 

You should also check the product’s ingredients to find out if there are acidic substances in the potting soil.

Examples of ingredients are expanded shale and decomposed granite, as they both produce acidity in the soil. These are great to give your soil a bit of an acidic boost. 

What You Can Do To Increase Soil Acidity

There are essential soil amendments you can make that will help you to increase your potting soil’s acidity if required. These include: 

Aluminum Sulfate

Aluminum Sulfate

This is a granular fertilizer that increases soil acidity quickly. Work it into the soil and water it a lot so that the aluminum sulfate is activated.

How to apply aluminum sulfate to your plants: 

  • Mix a quarter-cup of aluminum sulfate into a gallon of water. 
  • Add both ingredients into a watering can. 
  • Apply it to the established plant. 

Note: Make sure that you break down the aluminum sulfate into several treatments for your plants if how much you want to apply to the soil is more than 0.5 pounds over 10 square feet.

This is because putting too much aluminum sulfate in the soil at once can cause toxicity that will kill your plants. 

Coffee grounds

Since coffee grounds are very acidic, they will work well to increase soil acidity. This method is also a great way to make use of your used coffee grounds instead of throwing them into the trash.

Here’s how to add coffee grounds to your soil. 

  • Mix the coffee grounds into your soil. This balances the soil pH and provides acid-loving plants with more acidity. 
  • You can add it to the top few inches of soil or sprinkle the coffee grounds on top of the soil without working them into the soil.

Sphagnum peat moss

This type of moss is sometimes said to lower soil pH so that it becomes more acidic. But, it’s really only Canadian sphagnum peat moss that will lower soil pH as it has a pH of between 3.0 to 4.5.

Here’s how to add sphagnum peat moss to your soil. The method varies a bit depending on whether you’re using it in your garden or in containers. 

  • When adding sphagnum peat moss to your plants in the garden, you’ll need three inches of it. Mix it into the top 12 inches of your soil. 
  • When adding it to containers, add between ⅓ to ⅔ of peat moss into the potting soil mix. 

Fertilizer

Fertilizer

When using fertilizer to boost soil acidity, it’s important to use the correct one. Ammonium-based fertilizers have been found to have the most impact on soil and successfully increase their acidity.

Nitrate-based fertilizers, on the other hand, achieve this less effectively.

How to add fertilizer to your soil.

  • Make sure you read the fertilizer bag instructions. 
  • Generally, though, you should apply fertilizer around the plant base.

Mulch

This is a useful way to increase your soil’s acidity. Organic mulch will break down over time, providing more acidity to it. Ingredients in the mulch such as pine needles and oak leaves work particularly well to increase soil acidity.

Note that when you’re adding soil amendments, you should do so gradually and test the soil pH so that you don’t throw off its balance. 

Here’s how to apply mulch to your soil. 

  • Spread the mulch so that it’s approximately three inches thick. You don’t want it to be thinner than two inches otherwise this will enable weeds to enter it. It shouldn’t be too thick, either, as this will prevent water from entering the soil where it can be picked up by plant roots. 
  • After applying the mulch, make sure you water it. This will ensure it settles into the soil.  

Compost

It’s well-known in gardening circles that adding compost to plant soil helps to balance out its pH. This is as a result of its nutritious organic matter that breaks down over time.

Some of the best ingredients to add to compost so that your plants will get more acidic soil include: 

  • Rotten hardwood sawdust. Since hardwood is acidic in nature, rotted sawdust from this type of wood will boost the soil’s acidity a bit. It’s essential for it to have rotted, though. If you apply it to the soil without any rot, it will absorb nitrogen and stunt your plant growth.
  • Pomace. This dried pulp of fruits such as olives and grapes from cider mills is acidic so you can add it to your compost to raise the soil’s acidity. When applying it, do so in small amounts and check the soil pH regularly so that you don’t give the soil too much acidity at once.  

When adding compost to potting soil, mix about 25-50 percent of the compost with the soil. You can also add compost to the soil surface when the plant is growing.

Leaving it on the surface helps to deter weeds, but you can mix it into the soil if you prefer. Both methods provide a boost of nutrition to your soil. 

Can You Make Soil Too Acidic?

Can You Make Soil Too Acidic?

If your soil becomes too acidic, this can have various negative consequences for your plants. These include the following:

  • It causes nutrient deficiencies. High acidity in the soil causes deficiencies in phosphorus, nitrogen, magnesium, and potassium. Without these macronutrients, plants won’t be able to grow healthy. 
  • It promotes high amounts of micronutrients. Acidic soil disrupts the production of micronutrients such as iron in the soil, making them too high. This is toxic to plants. 
  • It causes the aluminum to get absorbed by plants. When soil is too acidic, aluminum that’s naturally present in the soil becomes toxic to plants. 

How to Test Soil pH

How to Test Soil pH

Whether you want to test the soil in your garden or in a potting mix, it’s easy to do – all you need are some ingredients you probably have in your kitchen or pantry.

A soil pH test should be conducted before you go ahead and try to boost the soil’s acidity or bring it down with alkaline-promoting ingredients. Otherwise, your soil pH will be off, causing a lack of plant growth.

Here are the steps to follow to conduct a DIY soil pH test:

  • Dig four inches below the soil surface. If you’re testing soil pH in potting soil, take a few handfuls of it and put them in a container. 
  • Remove any plant debris from the soil. 
  • Put one cup of the soil into a different container, preferably one that’s made of glass. 
  • Add distilled water so that the soil becomes muddy. 
  • Add half a cup of vinegar and stir it well. 
  • Check for a soil reaction. If the soil foams, bubbles, or becomes fizzy, it’s alkaline. 
  • If nothing happens, take another cup of soil you collected earlier and put it in a new glass container. Add the distilled water so it becomes muddy, as you did before. 
  • Add half a cup of baking soda. Stir it well. 
  • Check for a reaction. If it bubbles, foams, or fizzles, the soil is acidic. 

The above test will give you a good indicator of whether your soil is alkaline or acidic so you can make adjustments to it if necessary. 

Related Questions

Does baking soda cause acidic soil? 

Does baking soda cause acidic soil? 

Baking soda can be used to make acidic soil more alkaline. So, it’s a good DIY method to have at hand if you need to reduce how acidic your soil is to make it more suitable for your plants. It can also be used to test your soil for acidity.

Can you use lime to decrease soil pH?

Lime is used to lower soil acidity and increase its alkalinity. You should always be careful when using lime on your soil as too much of it burns the roots of plants.

Conclusion 

If you want to increase the acidity of your potting soil or garden soil, you need to ensure you get the correct ingredients that will successfully and quickly lower your soil pH.

In this article, we’ve featured some of the most effective methods to boost your soil’s acidity so you can grow beautiful acid-loving plants.

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