Why I can't start a successful plant with Rockwool

Alot of new indoor gardeners who are successful outdoor gardeners, usually run into this problem the first time they use Rockwool to sprout seedlings. While Rockwool is a perfect medium for clones to develop a root system, it is not recommended for sprouting seedlings.

Rockwool is basically a sponge with a nuetral pH. It contains no beneficial bacteria, micro-nutrients, or natural buffers which seedlings need in order to survive onto the vegetative state. While it is possible to successfully sprout seedlings in Rockwool, they are better designed to promote root growth from a clone or cutting.

Below are a few common mistakes which usually lead to the seedling's death:

• Over-watering; constantly keeping the Rockwool moist, or allowing it to sit directly in water.
• Using the Rockwool directly out of the package without flushing it first.
• Using large cubes (3" or bigger) for tiny seedlings
• Not checking the pH: allowing it to become to acidic or too alkaline

If you wish to start (or germinate) your seedlings in Rockwool cubes, then chose small plugs of 1-1.5" in diameter. This will allow the root system to quickly emerge through the cube so you can transplant it into Hydroton or Soiless mediums. This will give the roots access to the beneficial bacteria and/or nutrients introduced through your Hydroponic system or Soiless mix. Furthermore, make sure you flush your Rockwool cubes with water (or even h202), and never allow your cube to sit directly in water or to retain excess water (squeeze the cube like a sponge to remove excess water).

Transplant your Rockwool cubes into Hydroton, and cover the top of the cube with Hydroton as well.

If you only have large Rockwool cubes, then rip/cut them into small 1" square segments to germinate seedlings. Place them in a propagation tray & dome or cover them to retain humidity until they sprout. Once they are 2-3 days old, place the small cubes into your Soiless or other Hydroponic medium.