When we talk about houseplants or garden plants, we often think about light, watering, or fertilizer.
However, there is another element that is just as essential: the potting mix. It is often overlooked, yet it plays a central role in the health and longevity of your plants.
These two terms are often confused. Yet, they don’t mean the same thing.
- Substrate is a broad term. It refers to any growing medium in which a plant develops its roots. For example, this can include potting soil, sand, pumice, coco fiber, or a blend of several components.
- Potting soil or growing media is, on the other hand, one specific type of substrate. It’s a ready-to-use mix, designed to suit as many plants as possible. You’ll find it in bags at garden centers, often labeled as “all-purpose,” “orchid,” or “cactus” soil.
In short: potting soil is a type of substrate, but not all substrates are potting soil.
Each ingredient has its strengths and its limits. Therefore, understanding them helps you create the right mix. Here are the most common ones:
- Coconut fiber (coir): light and airy, it holds water well while avoiding compaction.
- Coconut chips: coarser pieces, perfect for aerating the mix and giving structure to the substrate.
- Pine bark: provides an acidic structure, ideal for acid-loving plants.
- Perlite and vermiculite: lightweight expanded minerals, very useful for improving drainage and soil aeration.
- Lava rock: volcanic stones that are highly draining and durable, perfect for preventing excess moisture.
- Pumice stone: a light, porous volcanic rock that improves aeration and drainage while still holding some moisture.
- Zeolite: a microporous volcanic rock that retains water and nutrients, then gradually releases them to the roots.
- Horticultural sand: adds weight to the mix and improves water flow.
- Clay pebbles: often used as a drainage layer at the bottom of pots to prevent water from stagnating around the roots.
- Worm compost (vermicompost): naturally rich in nutrients, it feeds the plant but must be used sparingly to avoid making the mix too heavy.
- Activated charcoal: absorbs toxins and helps reduce the risk of root rot.
- Sphagnum moss: a natural moss with a very high water retention capacity, very useful for cuttings or certain orchids.
- Peat (blonde, brown, black): widely used in horticulture, light and acidic with strong water retention. However, its extraction has a major ecological impact as it destroys peat bogs. That’s why it is increasingly being replaced by coconut fiber or green composts.
The roots of your plants do much more than just hold the plant in place. In fact, they breathe, drink, and feed.
A good substrate must, therefore, meet three essential needs:
→ Water: it should hold enough moisture to hydrate the plant. At the same time, it must let the excess drain away to prevent root rot.
→ Air: roots need oxygen. A substrate that is too compact or too wet will suffocate them.
→ Nutrients: a good substrate provides a natural reserve of organic matter. This reserve is then complemented by fertilizer.
In practice, a poor substrate often leads to watering problems. Either water stagnates and the roots rot. Or it drains too quickly and the plant dries out.
Garden centers often sell bags of “all-purpose potting soil.” They are presented as suitable for all plants.
In reality, these are standard mixes. They are convenient for general use: common houseplants, quick repotting, window boxes.
However if you really want to give a plant the best conditions, there is no truly universal substrate.
Each plant family – and sometimes each individual plant – has its own needs:
- Succulents and cacti prefer a very well-draining, almost mineral mix. It must prevent any water retention.
- Orchids naturally grow attached to trees. They need a very airy substrate made of bark, coconut chips, or sphagnum moss. A compact potting soil will not suit them.
- Ferns and tropical plants need a mix rich in organic matter. It must stay fresh and slightly moist, similar to a forest floor.
- Acid-loving plants (hydrangeas, camellias, Japanese maples) require a soil with a lower pH. Therefore, pine bark or ericaceous compost is often added.
In conclusion: so-called “universal” potting soil is a practical base. Nevertheless, it is rarely the perfect long-term solution. Adapting the mix to each plant type not only optimizes growth but also makes care easier. As a result, a good substrate helps balance watering and reduces the risk of root diseases.
At May Flowers Bee, I’ve chosen to offer you something unique: a custom potting mix prepared on demand.
Simply tell me which plant you’d like to repot and the volume you need. I will then create a tailored blend, made only with high-quality ingredients, carefully adjusted to your plant’s specific needs.
The result: a ready-to-use substrate, perfectly adapted, with no waste and no unnecessary stock at home.
A good substrate is not “just soil”: it is the key to a healthy plant, balanced watering and harmonious growth.
By choosing a suitable mixture, you offer your plants real living comfort… and you make daily maintenance easier.
