Potting Mediums Explained

To keep your houseplant the happiest it can be there are some basic needs you can satisfy. Sunlight and water are obvious needs but planting it in a potting material (“medium”) in which it can thrive is another important aspect. This blog will give you an introduction to different mediums you may run into throughout your houseplant journey. I will be telling you where each of them comes from as well as how and why they are used.

There are many organic potting mediums/soil amendments that are made by decomposition or harvested then dried. I wanted to also include inorganic, mineral and clay potting alternatives since these have become popular.

Organic Potting Mediums

There are many types of moss used for potting around the world but the most common are peat moss and sphagnum moss. Peat moss is an assortment of ground, dried grasses and moss harvested from wetlands in the northern United States and Canada. Plants with fine root systems such as begonias prefer peat moss heavy mixes.

Sphagnum moss is one type of moss often sold for potting. It is used both alive (as a soil topper and moisture retainer) and dry as a moisture retaining soil medium. It can be found very finely ground or in long strands. The long strand type is often used to mount plants as it holds a lot of moisture for many days while exposed to air.

Both of these mosses can be used on their own during propagation or for some plants long term. This will require added nutrients as dried mosses do not retain nutrients. Moss is also added to other soil mediums to create a balanced mix. If you use more, the soil will hold moisture for longer. Less and it will be a more well-draining but quicker to dry environment.


The most commonly used types of bark used for potting are Fir and Pine. They will often be labeled “Orchid Bark” because that is the main horticultural use for it. This bark is harvested from downed trees and provides a chunky additive to your soil mix. It can be found in different grades as well for different uses. The smaller chunks work very well for terrarium use. The bigger grades are used in soil mixes to provide drainage, oxygen, and moisture retention. Some plants such as some Epiphytic Aroids, Orchids, Hoya and Bromeliads grow well in only bark. In proper humidity, fine bark can make an excellent propagation medium for Hoya.

Coco Coir

Coco coir is a type of substrate that comes from the outer Husk of a coconut. The fiber is compressed and dried to form condensed bricks. These bricks come in many different sizes and is often bought in bulk. The uses for coco fiber are extensive in both gardening and houseplant growing but it is mainly used as a soil additive to retain moisture as it breaks down slower than other alternatives. When you buy a brick of it you will need a very large bin to expand it in. These coco coir blocks can expand up tofour times their original size once water is added.


I want to discuss soil because it may help you understand the difference between these materials and a simple potting soil you will find at the garden store. Soil is composed of minerals, organic matter, decomposing material and living organisms. The additives above like vermiculite and coco coir could break down to become soil but on their own they are not soil.

When you buy a houseplant soil bag it will often be a mix of perlite, worm casting or another organic material, and some bark chips. I find that these premade “soil” mixes do not work for all types of plants and often require additions to either make the soil more well-draining or moisture retaining.

Alternative Potting Mediums & Soil Amendments:

These following mediums are inorganic and work well as soil additives or on their own.


Leca is a clever acronym for “Lightweight Expanded Clay Aggregate”. Wow, that’s a mouthful! Leca comes in different sizes but is usually found as a pea size. The Leca starts out as small clay pieces and is expanded using heat to form the balls. This medium used alone is very well suited for semi-hydroponic growing as it does an excellent job of wicking water up towards the root system.

Leca can also be used in soil mixes or as a pot topper. In soil mixes It can help a lot with drainage if you have a mix that does not let water pass through easily. I use it alongside bark moss and soil to create a nutrient rich and chunky mix. The Leca is particularly greatbecause it is very porous which encourages the root systems to grab on to the individual pieces.


Pon is a soil-less mix produced by the brand “Lechuza”. Due to its high shipping prices hobbyists started it making it from scratch themselves. The mix includes:

  • 4 parts pumice
  • 2 parts lava rock
  • 1 part zeolite (which is a mineral composed of aluminum, silicon, and oxygen)

The main perk of Pon is that it creates an environment free of contaminants. Since it contains zeolite, the PH is also regulated which has a huge effect on the health of the plant. You are also much less likely to deal with problems with pests as they cannot lay eggs or breed in the without soil. Pon can be rinsed and reused over the course of years which makes it financially beneficial.

This substrate can be used on its own as a normal potting medium or in a semi-hydroponic setup (more about hydroponics below). When using it as a normal potting medium people find it needs to be watered once it looks dry. This is usually about two times per week.

Click here if you would like to nerd-out about zeolite.


Vermiculite is a naturally forming mineral made of a hydrated magnesium iron aluminum silicate mineral. It has a layered texture and is broken down to form the four different sizes it is sold in. Vermiculite is moisture retentive as well as oxygen rich. Another perk of Vermiculite for use in soil is that it has a neutral PH, and doesn't rot. Not only is it a great soil additive for houseplants, but it is commonly used in the garden to improve soil quality and drainage. Another common use of this soil medium is for propagation.


Perlite is what you see in your standard soil mix. It looks like little pieces of foam, but is actually made from volcanic glass that has been heated to 1000 degrees Celsius until it pops and expands to many times its original size.

Perlite is mainly added to increase the drainage of a soil mix but, unlike Leca or Pon, does not hold moisture for extended periods of time. It does not make a good substrate on its own unless used in a very humid environment as a propagation medium. Perlite helps to provide oxygen to the plants roots by dispersing throughout the soil. It also helps with drainage of water so that the soil does not become compact.

Thank you so much for reading this blog. Please share it with your fellow plant lovers and remember to tell them about my monthly houseplant giveaway!

Next month's blog will be about different plant types and their substrate needs. I will provide ideas for mixes and more information about potting.