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germinating cannabis seeds in rockwool

When your seedlings/cuttings have outgrown their blocks, you’ll need to move them into your hydroponic setup. Before we explain how to do this, here are the best and most suitable systems to use alongside Rockwool blocks.

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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.

Top Tips for Using Rockwool

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.

Soil growers often choose to start the process with seeds. But the process below is effective regardless of whether you grow in soil or hydro.

Upon mimicking a volcano, the factory machinery then needs to mimic the wind. The lava enters a spinning machine that whips it into thin strands of stone wool. The addition of some binding solution oil helps to hold the strands together. Another machine layers several sheets of wool on top of each other, then a conveyor belt passes them through a series of rollers that compress the wool into a dense mat and improve its structure.

If you’re growing in soil, you can transplant the Rockwool cubes directly into your new growing medium. Soil growers have a variety of choices when it comes to what to do next. You can transplant into plastic or fabric pots, place your plants into greenhouses or polytunnels, or plant them directly into garden beds.

Depending on how hot it is (and other factors) you may need to water your cubes 1-4 times a day. Use the Ph adjusted water when doing so (that’s why I had you save the leftovers from step 2). If you already threw that water out, go make another batch of Ph adjusted water and keep it in a separate bottle or container for watering. Note: Do not over water, in fact while some say to water 1-4 times a day, I did it only once a day when I got home after work.

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.

Here is what it should look like:

Important: Do not let the PH of the water go below 5. A Ph this low will damage the fibers of the Rockwool Cube

They should look like this:

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.

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.

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.