How to choose potting soil

How to choose potting soil for sowing, repotting and special plants

Choosing your potting soil is not a question of "brand" or marketing, but of structure, drainage and use. Depending on whether you're sowing seeds, repotting, or growing cacti, the right potting soil is not the same.

In this article, you will discover:
- the difference between sowing compost and repotting compost,
- how to make an all-purpose mix for 90% of situations,
- when to add sand or other components,
- and why it's wise to limit peat in your growing media.

What role does potting soil play?

Potting soil is not just "dirt", it's a growing medium that must:
- retain enough water for the young root,
- allow air to circulate to prevent asphyxiation,
- maintain sufficient fertility over several weeks or months.

A poor balance (too compact, too dry or too rich) can block germination, slow growth or promote root rot. lefigaro
So the idea is not to look for *the* perfect potting soil, but the right potting soil for the right use.

Sowing compost: what you need to know

A sowing compost is designed to support the seed during its first weeks.

🔍 Key characteristics

1. Very fine, homogeneous texture** to surround the seed without "gaps".
2. Low salinity** to avoid burning young roots.
3. Fairly high moisture retention** (it dries more slowly than a coarse potting soil).
4. https://www.gerbeaud.com/jardin/fiches/terreau-special-semis,1373.html

🌱 Ideal uses

1. Sowing in trays or cell packs (plug plants).
2. Fast vegetative cuttings (in water, leafy stems, etc.).
3. Young seedlings that will later be pricked out into a larger container.

⚠️ Limitations to be aware of

1. It can compact and become somewhat "waterlogged" (too wet) if left aside or overwatered.
2. It is not suitable, alone, for plants that stay in pots for a long time, as drainage remains poor.
3. https://www.lefigaro.fr/jardin/questions-reponses/2015/05/27/30010-20150527ARTFIG00254-semis-comment-reconnaitre-un-bon-terreau.php

Sowing compost is the plant's "cradle", not its permanent habitat.

Professional sites recommend working on a sufficiently large surface to avoid waste and make mixing easier
https://www.canna.fr/articles/structure-du-terreau-de-rempotage

💧 Managing moisture

Out of the bag, potting soil is generally already quite moist.
Once mixed and aerated, it dries quickly, especially in summer.
https://fertilaine.com/blogs/news/quel-terreau-de-rempotage-choisir-pour-vos-plantes-guide-complet
To prevent it from becoming difficult to rewet, store it:

1. either under a tarp,
2. or slightly moistened on the surface (light watering with a sprayer).

🧪 DIY tip for sowing compost

If you want to limit purchases but have both types of potting soil:

1. buy only a good quality repotting compost,
2. then sieve it (pass through a sieve) to obtain a finer mix.

A sieve can be simply made with a fan guard or any other fine-mesh support, allowing you to recover a portion fine enough for sowing. The rest goes back into the repotting compost: nothing is wasted.
https://www.minizap.fr/infos-pratiques/jardin/elaborez-vous-meme-votre-propre-terreau-de-semis_8540.html

Why not make your own potting soil?

Many gardeners dream of making their own "homemade" potting soil, but it's not always feasible.

The difficulties

1. Achieving a stable texture (no excessive compaction, no excessively large gaps) is technical.
2. Mastering fertility over several months is difficult without carefully studied inputs (compost, green manures, amendments).
3. Avoiding the presence of unwanted seeds and pathogens in a homemade compost or potting soil requires good control (temperatures, turning, raw materials).

Commercial potting soils are formulated to maintain good fertility for several weeks, which is particularly useful for a vegetable garden or nursery.
https://www.lefigaro.fr/jardin/questions-reponses/2015/05/27/30010-20150527ARTFIG00254-semis-comment-reconnaitre-un-bon-terreau.php

🌾 Economic angle for a professional blog

For a professional or large-scale grower (nursery, market gardener), the time spent making homemade potting soil is often more expensive than the cost of buying quality potting soil. actuepinal
The money generated from plant sales is reinvested in reliable growing media, which allows gains in quality, consistency and efficiency.
This doesn't mean it's impossible to make your own potting soil, but it should be considered a demanding project, rather than a quick and simple solution.

Conclusion

1. Sowing, plug plants, fast cuttings** → sowing compost alone or predominantly.
2. Repotting, pricking out, individual pots** → 50/50 mix of sowing compost + repotting compost.
3. Cacti, succulents, very low-demand plants** → 50% potting soil + 50% sand / perlite.
4. Long cuttings (bare wood)** → sowing compost + sand mix.
5. Peat: to limit if possible, in favor of coco coir, well-rotted compost and draining materials.

All about potting soil! How to choose it and use it well! (le jardin d'emerveille)