Horticultural Charcoal vs Activated Charcoal

Horticultural Charcoal vs Activated Charcoal

Charcoal is many gardeners’ secret recipe for healthier soil and plants, but not all charcoal is ideal or safe for your plants. There are several types of charcoal, with varying uses, so it is very important to understand which type is beneficial for plants.

Horticultural charcoal and activated charcoal are often recommended for gardening, since both have great benefits compared with regular charcoal. But what is the difference between these two types of charcoal? And which one is better for your garden plants?

This article will provide you with some valuable information about horticultural charcoal versus activated charcoal, and how to choose the best one for your garden.

What is horticultural charcoal?

Horticultural charcoal, also known as inactive carbon, is a charcoal in its purest form. It is lightweight and made from hydrolyzed wood, an organic material produced through a process called pyrolysis. Its density ranges between 2.0 and 2.1 grams per cubic centimeter, or approximately 1.2 ounces per cubic inch.

Growers often use horticultural charcoal to enhance soil quality and boost plant growth. Due to its moderately porous and low-density properties, it makes an excellent additive to enhance soil aeration. Horticultural charcoal can help sweeten the soil, too, by balancing its pH levels, making it an ideal and healthy medium for alkaline-loving plants and terrariums.

Another important property of horticultural charcoal is its ability to eliminate odors in terrariums and ward off certain toxins and fungal pathogens. It can bind to microorganisms, too – just like activated charcoal, albeit to a lesser capacity since it is not as porous as activated charcoal. Since it has a good drainage layer, this charcoal can provide adequate pore space for beneficial microbes to thrive.

What is activated charcoal?

Activated charcoal, or activated carbon, is created by burning carbon-rich organic materials like coconut shells, bamboo, hardwood, and coal. The process involves the extraction of methane, hydrogen, and tar, resulting in a lightweight, black carbon substance. It is then mixed into a chemical solution or steamed at high temperatures until all the non-carbon elements are removed. The result is pure carbon in its most porous form, that can bind with many elements.

Activated charcoal works like a sponge – it can absorb drugs and undigested toxins. This is the reason it is used as a medication to remove poisonous substances or overdosed drugs in the human body. It has also been proven effective in skin care, teeth whitening, and treatment of diarrhea.

When it comes to gardening, activated charcoal can also be beneficial. Gardeners mainly use it to remove certain chemicals that might be harmful to plants. It can absorb substances up to 33 percent of its own weight, and is very effective at eliminating offensive odors from compost. The only downside of using activated charcoal is that it also binds with beneficial allelochemicals and reduces the population of soil microorganisms, which can affect the growth and health of your plants. 

Horticultural charcoal vs activated charcoal – what is the difference?

The most noticeable difference between horticultural charcoal and activated charcoal is their porosity. Activated charcoal is far more porous than horticultural charcoal, since it is processed at a much higher temperature. For this reason, activated charcoal is more effective for filtration and is best used in the garden if you want to remove harmful chemicals and unwanted odors from your compost.

Additionally, activated charcoal is the more beneficial of the two for use in a sealed terrarium. You can also use horticultural charcoal, but it might not be as effective.

Activated charcoal can also be used for your garden plants, provided it does not contain added chemicals. You can mix it with your potting soil to improve the soil’s aeration, which will ensure your plants’ roots get more oxygen. 

On the other hand, horticultural charcoal like biochar would be more useful for soil amendment. Aside from being used as a filter, this charcoal also comes with added nutrients beneficial for most plants, unlike activated charcoal. It allows healthy soil bacteria to thrive while breaking down soil toxins. 

Horticultural charcoal is also designed to improve soil drainage, so you do not have to worry as much about overwatering issues. Choose a high-quality biochar like Char Bliss to make a bottom layer in the pot before adding your soil mix.

Can I use activated charcoal for plants?

As mentioned before, activated charcoal can be beneficial for your garden plants if your purpose is to remove soil toxins and offensive smells from the compost. Just keep in mind that it might also affect the growth of your plants as it prevents beneficial microbes from thriving in the soil. 

Which charcoal is good for terrariums?

Both horticultural charcoal and activated charcoal are beneficial for terrariums. However, since activated charcoal is more porous and absorbent than horticultural charcoal, it is often the best choice for filtration in a sealed terrarium. 

But, just like an ordinary sponge, the charcoal will eventually become saturated, so make sure to change the charcoal every two to four weeks to keep your terrarium clean and toxin-free.

Benefits of using charcoal in the soil

Whether you choose horticultural charcoal or activated charcoal, either of these will have a lot of benefits for your garden plants. Here are some of those benefits:

  • Charcoal has excellent absorbent properties. When added to the soil mix, it can promote good soil aeration and therefore protect plants from root rot.
  • Charcoal does a great job of assisting roots in absorbing soil nutrients while keeping the soil well-oxygenated.
  • Charcoal, particularly horticultural charcoal, helps keep the soil on the alkaline side. This soil-sweetening will help alkaline-loving plants grow to their full potential.
  • Charcoal is also excellent at filtering harmful bacteria and offensive odors, and can help absorb the impurities that might otherwise cause health problems in your plants.
  • Charcoal is often used for soil enrichment due to its ability to retain excess fertilizer and make it available for plants’ roots.

How to make charcoal potting mix for houseplants

Charcoal is an excellent additive to improve the quality of your soil. It is best used in conjunction with a nutrient-rich soil mix to ensure your houseplants grow healthily.

Use the recipes below to create a healthy charcoal potting mix for your plants. 

For succulents:

Mix one part activated charcoal with one part perlite and two parts soil.

For orchids:

When creating a charcoal potting mix for orchids, we highly recommend using charcoal chips instead of charcoal powder. Simply add one part medium charcoal chips to four parts medium-grade coco husk or fir bark, and one part perlite.

For tropical houseplants:

Add one part charcoal to three parts coir, three parts bark, and one part worm castings.

To improve the drainage of your pots, it is also a good idea to add a two-inch layer of activated charcoal at the bottom part of the container. Then put your soil mix on top of this charcoal layer. By doing this, you can help prevent root rot and fungal growth.

Horticultural charcoal vs activated charcoal – which is better?

Horticultural charcoal and activated charcoal each have their own unique qualities that might benefit your plants, depending on how they are used.

In general, activated charcoal surpasses horticultural charcoal for purification purposes since it is more porous and absorbent. Activated charcoal is also best for terrariums due to its excellent filtration capabilities.

Despite this, there might be times when horticultural charcoal is the best option. If you want to preserve the healthy microbes in the soil while still getting the benefit of filtering toxins and bad odors, then you should definitely consider horticultural charcoal for your garden.


Horticultural charcoal and activated charcoal are produced in two different ways, although they have several similarities when it comes to their uses. Activated charcoal is generally the best option if your only goal is purification. However, when it comes to soil amendment, horticultural charcoal would usually be the ideal choice.

Image: istockphoto.com / RHJ