germinating cannabis seeds in rockwool

Germinating cannabis seeds in rockwool

germinate them them move them to the rock wool cubes

Charlie Green

It’s easy:
get 2 paper towels
fold them in half together
place the seeds in-between the folded area
dampen the paper towel (damp, not dripping, but not too dry either)
place the damp paper towel with seeds in a ziploc bag
put them somewhere dark for a couple days
ta-da!

Well-Known Member

germinate them them move them to the rock wool cubes

Germinating cannabis seeds in rockwool

In hydroponic growing the plants’ roots get their nutrition directly from the watering solution. So you can use rockwool in hydroponics to start seeds, and you can move to larger sized rockwool cubes once rooted.

The MIXC humidity dome is great for starting seeds and the clear plant trays let you monitor root growth.

It’s easy to learn how to start seeds in rockwool cubes in a few simple steps. We’ll show you the best way to start seeds in rockwool cubes, how to prepare rockwool, when to start feeding seedlings, the best nutrients for rockwool, lighting for growing marijuana seeds, and when to transplant rockwool seedlings. This advice also works if you’re looking to start seeds in rockwool that aren’t weed seeds, the techniques are the same.

Best nutrients for starting seeds in rockwool

If you’re planning to use your LED light for your complete cannabis grow you should invest in a higher wattage model with a dimmer for when the plants are small.

When you add the seed you want it to sit in the bottom of the hole.

Rockwool is very alkaline so you need to go 5.5 with the pH to balance it out. You’ll notice a few leaves emerge, at this point your marijuana seed has successfully popped in the rockwool cube. Monitor the rockwool for dryness and aim to keep it damp, adding additional pH 5.5 water, rooting stimulant, and a very light nutrient mix.

Should I use a heat mat with rockwool cubes?

As your new marijuana plant sprouts from the rockwool cube it will begin growing roots. These roots will begin to poke out of the sides of the cube soon after the seedling emerges. Once your rooting system is growing strongly out the bottom and sides you’re ready to transplant rockwool seedlings.

Since rockwool is a hydroponic growing medium the plants will need to get all of their nutrition directly from your nutrient solution. But the new roots will be fragile so you’ll need to monitor your new seedlings closely to make sure you’re not over or under-doing it.

Germinating cannabis seeds in rockwool

Another tip I learned is to not squeeze out or shake out the water from the cubes. You want the cube to be damp as the wetness is what helps trigger the germination process.

Congrats! If you succeeded in getting your cannabis seeds to sprout you are now on your way to growing a healthy marijuana plant.

Now I had to mix a proper pH water solution to soak the cubes in. I filled a plastic food container with Brita filtered water (don’t think this is needed, but why not?) and added 0.25ml (a few drops) of pH Down. I stopped when I got to a pH level of 6.1.

Saving Some of the pH Adjusted Water

Instead of tossing away the reduced pH water I saved some in a separate container. As you wait for your seeds to sprout you may need to re-water the rockwool cubes if they get dry. Re-using this water saves you from having to mix up another batch of reduced pH water.

If you are using the rockwool cube germination method and have followed the procedure correctly it could take 2 days or up to a week for it to germinate. If it’s over a week there could be issues.

FAQ on Cannabis Seed Germination

I placed the cubes into the seedling starter tray and then inserted each seed about a quarter of an inch into the 1.5 inch cube. The seeds are really tiny so to help I used tweezers to place them inside the cubes.

That was good enough (I’m so trusting about stuff I read online) for me so I decided to proceed.