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how to start cannabis seeds in rockwool

Finally, the dense sheets enter a large oven. The heat activates the binding solution and enables the wool fibres to hold their shape.

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.

Is Rockwool Biodegradable?

Yes! Rockwool contains basalt, which works great as a soil amendment in general. Once it becomes weathered over time, it releases nutrients such as phosphorus into the soil.

3. Put your clones into cubes: Use a skewer to create a sizeable hole in the top of each Rockwool cube. Inset the stem of your cutting into the hole, gently pushing it so it reaches the bottom half of the block.

2. Nourish your cutting: Dip the cut tip of your clone into rooting gel to expose it to rooting hormones, nutrients, and trace elements.

Here is what it should look like:

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.

To accomplish this, use either Ph down chemicals, or lime juice (as it’s acidic). Add these to the water in small increments (VERY SMALL), and test the water to see where the Ph is. Continue doing this until you have a Ph of 5.5-6.

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

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.

About 2-3 weeks after germinating, you are ready to transplant these babies into the hydroponic system of your choice. A good rule of thumb to go by is that you want to transplant them once the first roots begin poking out of the Rockwool cube. Don’t wait too long though, as eventually the roots will begin tangling around the cube since it is their only source of water. You want to catch them right as they pop out, so that when you transfer them into your hydro system the roots will grow down into the system, and not just try to feed off the Rockwool cube alone.

Rockwool Cubes have a PH of roughly 7.8. This is pretty alkaline, yet our plants prefer to grow in a slightly more acidic environment (between 5.5 – 6.5). In order to prepare our Rockwell cubes for the seeds, we need to soak them in some PH adjusted water, that way they have everything the seeds need to germinate and sprout; water and a slightly acidic environment.

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.

But it also allows enough air exchange for the seed to produce a taproot and begin growing into a seedling.

Unfortunately, it’s not quite so simple.

Step 1: After buying your plugs or cubes, soak them in water until they are fully saturated.

How to germinate seeds with paper towels:

There are lots of factors that go into this method, and each must be nearly perfect for germination to occur.

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.

On top of that, Rockwool is like asbestos, you don’t want to be squeezing it or breathing it or generally touching it any more than you need to. Here is a good article on some of the health concerns of Rockwool. I use it because it is what works best, but be cognizant to the fact that it is a potentially dangerous substance to be making contact with so don’t do anything more than you need to with it.

Peat plugs hold more water than air compared to rockwool cubes, so they aren’t ideal for hydroponic grows.