Rockwool also poses a potential health hazard to growers. New Rockwool cubes can contain a lot of loose fibres and dust. These particles can end up in the air, and even on your skin and in your eyes, mouth, and lungs. Much like asbestos, tiny fibres can build up in the lungs over time if you work with new Rockwool cubes every day.
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.
Try and refrain from overwatering your Rockwool cubes during the seedling stage. They drain quite fast, and many growers get the impression that they’re underwatering. However, the inside of the cube remains nice and moist and will keep your seedlings happy without suffocating them.
To put your used Rockwool cubes to use, we recommend simply shredding them and tossing them onto your compost pile to recycle the nutrients within.
The process of making Rockwool cubes also takes a toll on the environment. In addition to the endless quarrying of basalt rock, it takes a considerable amount of coal energy to heat furnaces and power the machines needed to process the whipped-up lava wool.
Although they take a long time to break down, growers can shred their used blocks down as finely as possible and throw them onto the compost pile. Over time, key elements within basalt rock will leach into the compost and add a nutritional kick to your future soil.
Rockwool offers a long list of benefits to cannabis growers. Not only does it prevent pathogens from multiplying, but it helps seeds germinate and facilitates good drainage.
Some people claim they use a diluted nutrient solution to water their Rockwool cubes with during germination. Do not do this, as my experience has always been negative. Note the picture below, where I did an experiment by adding a very diluted grow nutrient to the Rockwool cube on the far left. It died within an hour or two, and the others went on to live happy lives. In my opinion, they do not need nutrients until they get into your hydro system.
In this lesson, we will learn how to start your own seed with Rockwool Cubes. Below is a detailed guide to success with Rockwool, and a step-by-step video tutorial can be found at the bottom of the page.
Get a bowl or some other container that is big enough to fill with water and have room left for your Rockwool cubes. Your average salad bowl will work fine for 3 Rockwool cubes, if you are planning on doing more than you will need a larger container.
Important: Do not let the PH of the water go below 5. A Ph this low will damage the fibers of the Rockwool Cube
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.
3 days. Once the first true leaves emerge, we want to select for the strongest one (the one that grew the tallest), and cut off the tops of all other seeds that are growing next to it. Do not pluck them out, as you may uproot it’s neighbors. Simply cut it off as close to the hole as you can without messing with the stronger one that you plan on keeping alive.
Rockwool Cubes are designed to maintain the correct water to air ratio and squeezing them may damage their structure. Some of the marijuana forums advocate doing everything from squeezing them completely dry, all the way to flinging them around like paintbrushes in order to get excess water out. None of that is necessary, leave it as it is. It will stay moist for several days without needing to be watered this way as well.
Here is what it should look like:
Cons of Rockwool
Cons of Rapid Rooters
Germination Method 3: Germination Station
This method is especially effective for seeds which have extra hard shells, or seeds which are older (more than a few years old).
For fastest growth rates, it’s better to plant young seedlings or clones in a very small container, like a disposable plastic solo cup.
If you look closely at the above plant, you can see that some of the newer leaves on this plant actually have 9 fingers. It is normal for there to be some variation between leaves – some plants will grow leaves with 11 or even 13 fingers. But the above guide will give you a general idea of what to expect.