Putting together the suitable soil for your indoor plant is critical for its appearance, root development, longevity, and overall growth. Getting the soil right is even more vital for houseplants because it becomes compacted over time in a pot. When soil gets compacted, air pockets get squeezed out, making it harder for plants to grow and for water to reach the plants’ roots.
For the general houseplant (excluding succulents), mix:
• 60% peat moss or coco coir, and
• 40% pumice, perlite, or other organic matter such as worm castings
The 40% component brings in aeration and nutrition needed for the soil. Pumice is recommended over perlite because it doesn’t float to the surface as the perlite does. Worm castings add food to the soil and break down slowly.
For succulents, mix:
• 66% mineral grit
• 33% organic soil
Mineral grit includes coarse sand, decomposed granite, gravel, and chicken grit.
Organic soil contains potting soil, forest products, compost, and coco coir.
When choosing a pre-made succulent soil in the nursery, look at the ingredient list and avoid ones containing:
• Vermiculite – this mineral retains moisture which is not suitable for succulents
• Peat moss – this fibrous material stores water when soaked and repels water when completely dry. So when you try to water the succulent, the water stills everywhere.
Below is further insight on each ingredient.
Peat moss contains decomposed sphagnum moss and other organic materials. When the sphagnum moss decomposes, it forms a fibrous and compact material. This material is non-absorbent and ideal for many different gardens (except for succulents), such as creating fertile soil to help plants grow faster.
If using peat moss for your indoor plants, you don’t need to water as often, saving you time and water in the home. If using a pot without drainage holes, the peat moss will absorb the water at the bottom that would otherwise remain and potentially cause root rot.
Coco coir is a by-product of coconut fiber. It’s the fibrous material between the inner shell and outer coating of the coconut seed. To be used for gardening purposes, it needs to go through a manufacturing process where the coir is extracted from the coconut, retted, de-fibered, and completed into a shippable product.
There are three types of processed coco coir:
- Coco pith – a dense, rich, and brown color that retains water exceptionally well.
- Coco fibers – stringy bundles that allow oxygen to breathe through the soil.
- Coco chips – small chunks of coco coir with a large surface area to retain moisture yet allow air to pass through them due to its chunky shape.
The benefits of using coco coir are that it:
• Allows plenty of aeration for the soil
• Is pH-neutral
• Has antifungal properties that reduce the risk of pests
Perlite is a form of amorphous volcanic glass and has the appearance of Styrofoam pieces. It’s often used as an amendment to the gardening soil to allow better water drainage. It’s non-toxic, clean, lightweight, and easy to use.
Perlite comes in various grades of fineness.
The coarse perlite will have the highest air porosity allowing the best water drainage. This is ideal for cacti and succulents that cannot cope with heavy soil moisture. The bigger perlites will hold onto the soil better and won’t be blown away by the wind coming from the window sill.
The finer perlites are used for seed-starting mixes and root cuttings. It fosters more robust root formation than grown in water alone.
Pumice is a volcanic rock that is produced when lava, water, and gas content has erupted. The rocky material is formed as a result of lava cooling and hardening. Its feather-like weight allows it to float but sink once it becomes waterlogged. The rock is porous and doesn’t decompose or compact over time like many other soil amendments.
Its porous nature makes it ideal for cacti, succulents, and other plant species requiring good drainage and air circulation. The porosity also allows microbial life to thrive while maintaining soil structure. For plants that are more prone to rotting, add more pumice into the soil mixture to allow better air circulation into the root system.
Pumice is preferred over perlite because it’s a heavier material, so it doesn’t float or blown away easily as perlite. It also lasts longer than perlite. However, it’s often more challenging to find pumice in stores and is more expensive.
Vermiculite is a naturally occurring mineral that is lightweight, non-toxic, and does not deteriorate over time. It’s highly absorbent of water and retains up to four times its weight. Vermiculite attracts plant nutrients such as magnesium and calcium, making it an excellent choice for propagation and houseplants that thrive in moist soil.
Avoid using vermiculite when planting for succulents and houseplants that get minimal sunlight. The high water retention properties of vermiculite will cause root rotting and succulents to die from over-watering.