Horticultural Charcoal: What Is It And How Do You Use It?

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Horticultural charcoal is an unprocessed type of carbon used as a mild soil amendment. Use it to help drain excess moisture from potted plants, terrariums, and other containers.

How do you use it? The general rule is that you mix two cups of horticultural charcoal for every cubic foot of potting soil. In simpler terms, use one part of charcoal for every 10 parts of soil.

Horticultural Charcoal for use in potted plantsPin

Are you looking to learn more about horticultural charcoal? This post highlights what you need to know about its uses and benefits, so stick around.

What Is Horticultural Charcoal?

Horticultural charcoal, or inactive carbon, is charcoal in its purest form. It’s an organic material manufactured through a process known as pyrolysis.

Adding horticultural charcoal (biochar) to a potted plant boosts plant growth and health. When used in terrariums and vivariums, it helps destroy odors. It’s also known for its ability to ward off fungus and toxins.

It provides the high surface area, carbon-rich, organic medium necessary to perpetuate springtail breeding and promotes denser springtail colonies. 

Charcoal for Plants The Origins

Several materials can make up horticulture charcoal. The best are hardwoods such as oak, hickory, maple, and walnut.

They’re easy to come by and cheap to process, which is one of the reasons why horticultural plant charcoal is affordable.

It is obtained by burning carbon-rich materials, such as wood or coconut shells, at very high temperatures through a process called pyrolysis. 

Some of the other more common porous materials used to make inactivated carbon include:

  • Wood
  • Coal
  • Peat
  • Coconut

The Benefits and Answer – Is Charcoal Good For Plants?

Improves Moisture Drainage

Activated charcoal is our preferred base layer for planting in pots without drainage holes. 

One of the main benefits of horticultural charcoal is its absorbent properties. Its porous capability helps absorb excess moisture, which protects plants from over-watering.

It lightens and aerates soil increasing oxygen for healthier plants and increasing living space for microfauna.

Enhances Plant Growth

Acting as a substrate, this type of charcoal provides air pockets and aeration to the soil. Plus, it gives roots the room they need to grow and thrive.

Roots that are sat in a saturated environment won’t be able to breathe properly, so it’s important that excess water can drain away. 

It shouldn’t be a problem below the substrate, but if the plant’s roots reach there, then it could be. 

Horticultural charcoal for plants does a great job of helping roots absorb as many nutrients and minerals from the soil as they can. It also helps keep oxygen within the soil, aiding in further nourishing the plants.

Boosts Soil Preservation

Also, horticultural charcoal prolongs the life of houseplant soil. One of the ways it does that is by balancing pH levels.

So, it has that advantage over other organic soil amendments like orchid bark which will break down slowly over the course of a few years.

Another way it helps the soil media is by ‘sweetening’ it. In other words, it keeps the soil’s pH levels over 7.0, which means it’s more alkaline than acidic.

Easy to Use

Horticultural plant charcoal easily shakes out of pots and containers of indoor plants. It doesn’t snag or tear the roots, making it easy to transport plants between pots.

Use a thin layer of charcoal in plant terrariums, reptile cages, pots without drainage holes, and outdoor potted plants.

Filters Harmful Bacteria

Naturally detoxifies, cleanses, and absorbs excess water from its porous pieces. Acts as a filter and also retains moisture while removing excess moisture for your plants. Great for terrariums, gardens outdoors, and as a soil conditioner.

Another benefit of horticultural charcoal is its ability to filter toxins and microbes. It helps prevent odor build-up caused by bacterial and fungal growth. Plus, it’s excellent at absorbing impurities to keep your plants healthy and disease-free.


The main drawback of using horticulture charcoal is its raised pH levels. Biochar contains a large portion of ash content.

As a result, this can cause alkaline levels in the water and soil to rise to unwanted levels. It is counterproductive for perfect plants that thrive in acidic environments.

How To Use Horticultural Charcoal?

There are several ways to prepare and use charcoal, depending on where you use it. Below are some common uses for horticultural charcoal for plants.

Bag of horticultural charcoal, in small, irregularly shaped pieces and almost black color.Pin

Perfect for terrariums, cachepots, and other closed planting vessels and suitable for use with all houseplants!  Add to any garden soil mix, potting soils, or organic matter to improve aeration, moisture, and drainage. 

Potted Plants/Terrariums

What plants like charcoal? Horticulture charcoal works best in potted plants and terrariums that don’t have drain holes. It’s also ideal for outdoor potted plants that endure heavy rainfall.

You don’t have to do much when using this type of soil additive.

  • Lay down a 1″ inch layer of rocks or pebbles.
  • Add a ½” inch layer of horticultural charcoal.
  • Add about 1″ inch of the primary substrate or potting soil.


The best way to use horticultural charcoal in aquariums is to add it right after the tank’s mechanical filtration.

Adding the charcoal before this will cause it to absorb debris from the tank. As a result, the charcoal layer will expire at a much faster rate.

Reptile Vivariums

Preparing horticultural charcoal for a vivarium is easy. All you need to do is give it a quick rinse with reverse osmosis (RO) water to help remove tiny fragments and debris.

Avoid rinsing the charcoal with regular tap water. The charcoal will absorb the chemicals in the tap water, which will speed up its degradation.

After that, place a layer of charcoal into the tank. Keep in mind that the charcoal will continuously filter the air around it. So, you’ll need to replace it each month to keep the vivarium in optimal condition.

Another type of charcoal used in horticultural settings is wood ash, which is easily made from plant materials at home. Wood ash can be especially helpful in gardens and lawns to add required nutrients. 

A Final Note

Horticultural charcoal is like pumice. It’s a drainage layer that boosts water retention and aeration. It’ll make a nice addition to your potted plants, terrariums, or aquariums.

If you’re looking for an affordable, low-maintenance drainage layer, why not give horticultural charcoal a try?

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