Growing Media

Soils, substrates and growing media for successful growing. Rock wool and useful accessories for growing cuttings also make it easier to get started with home growing.There are various factors that determine the ideal substrate for growing in pots or other containers. On the one hand, which medium to choose depends on the needs of the plants, and on the other hand, there are substrates that are not suitable for every type of cultivation. However, the path to the perfect substrate is not difficult, because whether coconut fibre, soil or hydroponics, there are pre-prepared substrate mixtures for every variant and every phase - from very nutrient-poor growing media, which can be adapted to the plants themselves by adding specific fertiliser, to completely pre-fertilised mixtures, to which hardly any more fertiliser needs to be added during the entire growing period.

Which substrate is the right one for my grow project?

In order to find the right medium for the plant and cultivation system, the medium's water Storage capacity, air permeability, sterility and pH value are important.

Water storage capacity of a grow medium

How do you find out the water storage capacity of a medium and what influences it? If you look at the water storage curve or values for the hydraulic conductivity (absorbency) of a medium, you will quickly realise: Different substrates absorb water at different rates, distribute it over the entire surface at different rates and release a certain amount of it back to the plants sooner or later, which is referred to as specific water availability.

The finer the pores of a substrate, the more water it stores in a very small space. Very fine-pored media can absorb water well, but can also store it for such a long time that it becomes unavailable to the plant and cuts off its air supply instead - this happens especially when the water in tall pots with a substrate with a high water storage capacity stands very high for a long time.
A medium with a low water storage capacity requires much more frequent watering, but you don't have to worry about aeration of the roots. The opposite is true for a fine-pored grow medium that absorbs a lot of water.

When growing in very humid climates, it is advisable to choose a medium that does not have a very high water storage capacity in order to avoid mould and mould damage - similarly, you should protect your plants from evaporation with a good water storage medium if you are growing in very high ambient temperatures and low humidity.

Air supply and porosity

A distinction must first be made here between total porosity, which is only relevant for root formation, and the so-called 'air-filled' porosity, which is relevant for air supply and only accounts for around half of the total porosity. In general, the porosity of a substrate mixture determines how much space remains in the plant pot for water, air and root growth. Where media with rather small pores have their strengths in water storage, coarse pores, i.e. more porous substrates, leave more space for air and roots. The more porous a medium, the faster the drainage.
The shape of the plant container also plays a role in the air supply to the plants - the higher the pot, the higher the porosity of the medium towards the top. Shallow containers, on the other hand, increase the water absorption capacity.

Sterile and chemically neutral substrates to regulate the pH value

A sterile medium is easier to control than a substrate that already contains soil life. Such a substrate with a low cation exchange capacity makes it possible to determine the nutrient supply and thus the growth conditions for the plants very accurately with the help of nutrients and soil additives. At the same time, such a grow medium makes it much easier to avoid salinisation and regulate the pH value.