Many cannabis growers and businesses are making the switch to more sustainable and environmentally friendly products and methods. The idea of used Rockwool cubes sitting in a landfill site repels some cultivators. Because many growers still don’t make their own compost, and don’t want to go to the effort of shredding up their cubes, this is exactly where many Rockwool cubes sadly end up.
These small particles are classed as “fine mineral fibres”, which the Environmental Protection Agency (EPA) in the United States has identified as probable human carcinogens  .
Here are some final tips to reference so you can master using Rockwool to grow cannabis.
Shred your used Rockwool cubes into fine strips before adding them to your compost pile to speed up the rate at which they release minerals into the soil.
Cannabis plants have different nutritional demands during the flowering stage. Clean out your hydroponic nutrient reservoir and fill it back up with a flowering formula. If you’re growing in soil, start watering your plants with bloom nutrients to ensure big, healthy buds.
Technically, no. Because Rockwool contains no organic material, microbes such as fungi and bacteria won’t break it down in the same way they would food scraps, leaves, and twigs.
Rockwool cubes are sterile and inorganic. After being exposed to extreme heat, Rockwool arrives at a grower’s doorstep clean and ready for use. Because it doesn’t contain any organic matter, Rockwool helps to protect the root zone against damaging microbes.
germinate them what ever method you prefer to use,
you dont use a humidity dome for starting seeds and second rockwool cubes will not dry out. they retain allot of water, and with
Pre-sprout your seeds in a moist paper towel and then plant in the rock wool once the spouts are over 1/2" I did this and got 14/20 sprouted from which I had to pick 7 and they are all doing AMAZING.
once split i transfer to cup with holes in bottom covered with a baggie and rubber band for a little greenhouse effect once soil break i remove plastic once again all heating pad .. i normally use heating pad until first transplant at 3 or 4 weeks old
i would have soaked mine over night first 75 percent of time is split the next day
Items you will need:
Step 2: After soaking at least 12 hours, use sterilized tweezers or clean hands to remove the seeds. Immediately place the seeds into your medium, such as a plug or soil.
Now that we have the Ph adjusted water, it’s time to stabilize and hydrate the Rockwool cubes in it. Insert the Rockwool Cubes into your container and let them soak for roughly 1 hour. Once the hour is up, the cubes will be big and fat with water. Take them out of the bowl of water and put them somewhere you don’t mind getting a little wet. Save the remaining water for step 3.
Now, if you can, place them in a tray with a dome on it. This will help create a little humidity in there which seedlings like. This is not mandatory, but it helps. Whichever you choose, take your cubes and put them in a cool dark place, and leave them alone. The temperature should be roughly 68 degrees F, though my house stays at about 72 and they do fine there. I usually place them above my refrigerator and just leave them for a day or two. My lettuce seedlings sprouted with a quickness the last time I tried, and by the 3rdday they had grown so tall that I had to take the plastic dome off of my container because they were bumping up against the ceiling.
If you don’t plant deep enough, the seedling may dry out, or never become moist enough to germinate.