Rockwool is hands-down one of the best growing mediums for germinating and raising seedlings, thanks to its high aeration and good water retention. It is easy to use and hard to fail with. Rockwool is made from molten rock that is spun at high heat (similar to fairy floss), giving a light material with thousands of tiny cavities that store water and air.
Main features of rockwool
High success rates
Sterile
Great water retention
Great root aeration
Affordable and easy to use
Light weight
Using rockwool for germinating seeds
Soak the rockwool cubes fully, then place 2 to 3 seeds in the hole at the top of each cube. Wet the seeds with some water to help them germinate, and keep the cubes sitting in about 1cm of water so they stay hydrated. To improve germination, cover them with a clear glass or plastic container to create a warm, humid greenhouse effect that can speed up sprouting.
Using rockwool to root cuttings
Cuttings root well in rockwool too. Soak the cube in water, then cut the parent plant as you normally would (usually just below a node on the stem) and trim off any unnecessary leaves. Dip the cutting in rooting hormone (optional) and embed it slightly in the hole at the top of the cube. Keep the cutting in bright, indirect light.
Rockwool is stable and has no adverse environmental impacts. It can typically be disposed of in ordinary landfill, although local regulations may apply.
