We have heard or read on the plant tag from nurseries that most plants require well-draining soil. But what is well-draining soil? Is the potting mix that you get from the garden center well-draining enough suitable for indoor conditions? We will try to answer these questions in this blog post.
What is well-draining soil?
In simple words, well-draining soil is a substrate medium that provides the plant roots enough oxygen as well as water. Such soil mediums do not drain water too fast nor too slow. If the medium consists of more sandy substances, then water might drain too quickly that the plant roots cannot absorb water. But if the medium is too clayey, the water might drain too slow and might puddle and form pools in the soil. This will not allow the absorption of oxygen by the roots leading to rotting of the roots.
For almost all plants, we need a medium that drains water at a moderate rate allowing air pockets to form in the soil for the roots to breathe. Improper water intake by the plant can invite plant diseases and pest problems.
Let us see how we can make such a medium at home. My goal, while writing this article, is not to give a prescribed formula for well-draining soil. Instead, make you aware of certain factors that you have to consider before mixing your own potting soil. The materials I use below can be replaced with any other equivalent that is locally available at your place.
Ingredients for well-draining potting medium
Let us get straight into the recipe. Broadly, a potting medium should consist of 3 parts.
1. Substrate
The substrate is usually something to hold the plant. As a substrate, we could use normal garden soil, the indoor potting mix we get from the store, coco peat, etc. I use cactus soil mix as my main substrate for indoor plants. It already consists of normal soil, sand, and some perlite. We can go ahead use only this for our indoor plants, but I feel it is still not well-draining enough. That takes us to our next ingredient.
2. Drainage
This is the key ingredient that determines how well-draining our medium can be. As drainage, we could use, perlite, vermiculite, sand, gravel, orchid bark, etc. All these materials can make the medium more airy and porous allowing oxygen intake by the roots. I use a mixture of perlite, orchid bark, and coco peat for drainage. Orchid bark and Cocopeat not only provide drainage but can hold a little bit of moisture without making the medium dense.
3. Nutrients
The last ingredient in the potting mixture is something to nourish the medium. For this, you can use compost, worm castings, cow manure, horn shavings, bone meal, etc. I use worm castings or homemade compost whichever I have with me at the moment. They are slow-releasing fertilizers that are not going to be heavy on the plants.
Soil Composition
I have explained the ingredients required for mixing the potting soil and also shared what material I choose for each ingredient. But that is not enough to complete a recipe. We need the measurement of each ingredient.
The percentage of mixing these ingredients depends on several factors like
- Moisture requirements of the plant
- Location of the plant
- Type of pot the plant is potted in
- Your tendency to water plants. Do you tend to underwater or overwater your plants? 😉
We can broadly classify the plants based on their water requirements into three main categories.
1. Plants with moderate water requirements
Most of our plants hailing from the tropics like Pothos, Philodendron, Monstera belong to this category. They like their medium not too dry and too wet. But they prefer their soil to be dried out in between waterings.
For most of my tropical plants, I use 60 % of the substrate itself, in my case cactus soil, 20 % perlite, and orchid bark mixed for making the soil more airy and porous so that it has better drainage and the rest of the 20% is compost or worm castings to provide nutrition for the plants.
This is not a strict formula I follow. Most of the time I eyeball the amount of each ingredient. Once I get the feeling that the soil is well-draining enough, I go ahead and pot the plant.
There are two other categories of plants for which this formula should be changed a little bit.
2. Plants with low water requirements
On one end of the spectrum, we have plants that like their substrate dry for the most part. Plants like the Snake plant, ZZ, Cactus, succulents all come under this category. What I would change in my formula is that I will not add orchid bark as they hold more moisture which these plants don’t want. Instead, I will increase the percentage of Perlite to provide more drainage to the mixture.
3. Plants with high water requirements
And on the other end of the spectrum, we have moisture or humidity-loving plants like Ferns, Calatheas, peace lily. For them, I add less perlite and more orchid bark or cocopeat as they can retain moisture without making the substrate dense.
So that is generally how I mix my potting soil for the indoor foliage plants.
Advantages
We could actually use the same mix for all plants and not make it this complicated, it should be okay but then you have to water your Calatheas or Ferns more often and succulents less frequently. But if we change the formula a little bit according to plant needs, we can mostly get away with one watering day for almost all the plants. This is the main motivation why I use the different potting mixtures for different types of plants.
Anyway, I suggest you choose a well-draining potting soil, preferably mix your own because often I have seen the mix you get from the garden center is quite dense and does not drain water.
As I mentioned before, you could also change this formula a bit according to your tendency to underwater or overwater your plants. If you tend to underwater your plants, add more cocopeat or orchid bark so that they retain moisture, but if you tend to overwater your plants, reduce the amount of these elements, add perlite instead.
I hope you get the idea of mixing your own potting soil. Now that my potting soil, my plants are waiting to be repotted before summer starts. If you have any questions or remarks kindly comment below. I also have a video on how to mix potting soil for indoor plants on my channel.