Potting compost, also known as seeding compost, provides seeds and cuttings with optimal conditions for germination and growth. Here is how you can easily make the substrate yourself.
Many gardeners swear by homemade potting compost. Not only is it cheaper than purchased, but almost every gardener has most of the ingredients for this soil in their garden: loose garden soil, sand and well-matured compost.
Why use special potting compost?
There are several reasons for using special soil for growing plants. First of all, conventional garden soil usually does not contain enough humus and is also often clayey, an unfavorable combination for root formation. On the other hand, potting compost is largely made up of humus and sand. It is airier and looser, but at the same time can store a lot of water. In this way, the plant growth is optimally supplied with moisture and oxygen.
However, it is much more important that seeding compost is largely germ-free ,i.e. free of pests and fungal spores. This is important because the sensitive seedlings and cuttings do not yet have good defenses and are easily attacked by mold and other typical fungal diseases. In addition, potting compost is much lower in nutrients than normal garden or flower soil. This has the advantage that the plant has to actively search for the few nutrients and thereby forms more roots. If you later transplant it into a more nutrient-rich soil, it can then absorb nutrients better and grow faster.
How to make your own potting compost
To make your own typical potting compost, you need just a few ingredients: one-third garden soil, one-third medium-grain sand, and one-third well-matured compost. The garden soil should be loose and contain as few weed seeds as possible. Therefore, it is best not to use the top layer of soil, but first dig off 5 to 10 cm (2 to 4 inches) of soil. Very good alternative is the soil of molehills as a basis for a homemade sowing soil.
The individual ingredients are sieved and then mixed well. To kill rot, mold and weed seeds, as well as larvae of fungus gnats and other animal pests, the mixture must be sterilized before use. This can be easily done at home in the oven. To do this, put the mixture in a discarded roaster or on an old baking sheet and steam it in the oven for about 45 minutes at 120 °C / 248 °F. After that, the potting soil just needs to cool down and can then be used immediately for sowing seeds or growing cuttings. Seeding soil is generally not fertilized, as the nutrient salts can damage the roots of the seedlings and the tender little plants can then turn yellow or care.
In addition, mix a few handfuls of Perlite granules into the growing medium. This ensures better aeration and increases the germination rate. It also makes sense to add algae lime or stone powder as a basic supply of trace elements.