Always fertilize the rockwool when you irrigate and allow for some drainage every time to wash off any excess fertilizer. The appropriate level of runoff should not exceed 30%, which means very little water should come out the bottom of a rockwool block.
Rockwool cubes, like most rockwool products are wrapped in an opaque plastic foil. This wrap has the same function as the walls of a plastic pot—it keeps the light out and the roots in. By covering the wool, it also prevents the growth of unsightly, yet harmless, algae.
In all cases, let the rockwool drain freely until water is no longer running out of it. Air will re-enter the largest pores, achieving the perfect balance between air and water in the medium. No squeezing or wringing is required.
Don’t: Overwater Plants in Rockwool
To prevent issues due to the presence of rotting roots, you can simply treat the used rockwool with enzymes. Your local hydroponics shop employees can help you with this.
Plants always take up water at a higher rate than nutrients, so expect some increase in the concentration of fertilizer salts inside the medium between waterings. Furthermore, not all nutrients are taken up by the plant at the same rate, which creates nutrient imbalances and modifies the pH over time.
If you irrigate with just water, the fertilizer concentration in the block will drop and may cause a slight shock to the plant. Rockwool has a tremendous capacity to retain water, so it is better to irrigate less often with a well-balanced nutrient mix than to water more frequently without the nutrients.
Do: Keep the Wrap On Rockwool Cubes
Grower displaying roots of a cannabis plant grown in rockwool. – OpenRangeStock / Shutterstock
It's best to keep the plastic wrapping on your rockwool cubes. – AJCespedes / Shutterstock
Let’s first understand that rockwool is made from basalt, a volcanic rock composed mostly of silica, with small percentages of titanium, iron and other elements.
Understanding The Rockwool Presoak
As a hydroponics marijuana grower, you need total control over how your plants absorb water, oxygen, and hydroponics nutrients. Fact is, what you choose as the environment for your cannabis…
Professional Rockwool Management Technology
Soaking rockwool cubes and slabs is easier than soaking loose rockwool.