Rockwool is what we call an inert substrate. This means that the medium itself does not contain any nutrients whatsoever. All the nutrients the plant requires are added through watering it. Although there are more inert substrates available, people who grow this particular plant use rockwool. The advantage is that the whole system can be made fully automatic which saves a lot of time and the yield is higher than when growing in soil.

The basic principle of growing on rockwool is that the plants are placed in a growblock, on a rockwool slab. Near each plant a dripper is placed which is connected to a pump (in the reservoir with nutrient solution) that, connected to a timeclock, waters the plants at set times and provides them with the nutrients they need. In this way the nutrients are immediately available for the plant and at the same time leaves enough oxygen for the roots because of the porosity of the rockwool. The solution is kept at the right temperature with an aquarium heater (23 deg C)

Relatively new for the Australian market must be the use of separate propagating or seedling blocks; in Holland most growers work with this system because it is cheaper, safer and takes up less space. In the cloning stage you can put 4 times as many seedlings or cuttings under a lamp when you use the 2x2 or 4x4cm blocks than when using the 7.5x7.5cm blocks. You can check the progress and detect weak ones much better because the roots are visible sooner. If the cutting fails you only spoil a small block instead of a more expensive large block. These small seedling blocks need to be placed in a grow block with a matching hole in it. e.g. A 2x2 cm propagating block fits a 7.5x7.5 cm grow block with a 2 cm hole.