What Is Horticultural Charcoal And How Do You Use It?

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 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.


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 charcoal is affordable.

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

  • Wood
  • Coal
  • Peat
  • Coconut


Improves Moisture Drainage

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.

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.

Horticultural charcoal 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 the soil. One of the ways it does that is by balancing pH levels.

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 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.

Filters Harmful Bacteria

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 horticultural charcoal is its raised pH levels. Horticultural charcoal 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 plants that thrive in acidic environments.

How Do You 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

Potted Plants/Terrariums

Horticultural charcoal works best in potted plants and terrariums that don’t have drain holes. It’s also an ideal option for outdoor potted plants that endure heavy rainfall.

When using this type of soil additive, you don’t have to do much.

  • 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.

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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