Growing With Rockwool

An article describing not only how to use and reuse rockwool, but also the health hazards surrounding its usage.

Rockwool is a very easy and clean planting medium to deal with. It is an environmentally safe product, but in some forms it can be hazardous to your health. When used in your garden rockwool can be a medium that aerates your roots(increasing growth up to 30% via oxygenization), allows water and nutrients to pass over the root system with ease(increasing nutrient uptake levels) and can be reused if properly sterilized.


Rockwool is a very easy to work with material and can promote extremely fast growth. Rockwool is bought in slabs, bricks, cubes, and rockwool flocking is stuffed into containers. To start your seeds in rockwool simply press your seed into the rockwool (brick, slab, or cube) to the desired depth. If using rockwool flocking, place it into the container (size of container is optional) and cover with the flocking until it covers your seed to its needed depth. After you have planted your seeds completely saturate the rockwool with water, and keep the medium moist. Rockwool should be dealt with like soil, except for the fact that its treated, in watering, as a hydroponic medium. An all-purpose fertilizer should be applied in every watering, using the recommended usage instructions on the box.


Rockwool can be "recycled" and used again in your garden by sterilizing it. Most gardeners don't use the medium more than once, not wanting any plant diseases or insects to be transferred to the next crop, but any infectious agents can be killed by sterilizing it properly. Some people use a cup of bleach in a gallon of water, but bleach has unhealthy chemical fumes and is environmentally unfriendly. I suggest using hydrogen peroxide at a rate of 1 pint per gallon of water, and thoroughly soaking your used rockwool in this solution for about a day and then repeat. The hydrogen peroxide should break down into water in about a day or so and your rockwool will be ready to start a new crop. Rockwool slabs and bricks have been used by rose gardeners for up to two years at a time.


Although rockwool is a very useful growing medium, it can be hazardous if not handled properly. Always wear gloves when working with rockwool, its small strands can form splinters and pierce the skin. A small portion of the population is allergic to rockwool and can form rashes and leave your skin irritated. When working with rockwool flocking always wet it down completely before moving it around, the particles break off easier in the flocking and become airborne easily. Some of these particles can land in your lungs and cause a temporary ulcer where they pierce the skin. After the rockwool pierces the skin its alkaline properties interact with the bodies acidic environment and the rockwool dissolves, but wearing a mask to cover your mouth andnasal passages would be advisable. Aside from a few minor complications, which can be taken care of with some protective gear, rockwool should prove to an asset in your indoor or outdoor vegetable garden.

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