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  .
Once your seedling looks ready for a new home, you’ll find it incredibly easy to move it directly into a pot full of soil or a hydroponic net pot. Unlike transplanting from soil, you don’t need to break apart the initial growing medium or deal with any mess. Simply pick up the cube and slot it into its destination.
There are many benefits to growing cannabis with Rockwool, especially when doing so hydroponically.
Some growers attempt to squeeze their cubes like a sponge to remove excess water. Don’t do this! They drain fine on their own, and squeezing them will damage the cube and the root system of your seedlings.
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.
Second, consider wrapping a rubber band or soft garden tie around the middle of the cube to ensure it doesn’t break in half during the next grow.
However, healthy soil doesn’t just contain organic substances. Vital minerals and elements required by plants are inert by nature. Some of these are locked away inside of Rockwool and will eventually end up inside your cannabis plants, where they’ll enable and support key physiological functions.
I use the paper towel method 100 percent success rate for me, then once the little white tail pops out of the seed, then move the seeds to the 1 inch rock wool with the tail facing down in the hole then lightly put a little piece of rock wool over the hole that the seed is in.
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
germinate them them move them to the rock wool cubes
another ethod that ive HEARD works is just to put in a shotglass over night, see what happens ins the seed absorbs the moisture until it pops. thats what ya want..
i have a Hydro set up also so i have been starting seedlings in rockwool for years.
Using either a PH test kit or a Ph meter, determine the Ph of the water. Water comes out pretty alkaline, usually around 7.4, so you will need to acidify it a little bit to bring that Ph down to the desired level. Aim for as close to a Ph of 5.5-6 as you can get.
If you don’t plant deep enough, the seedling may dry out, or never become moist enough to germinate.
Step 1: Hydrate And Stabilize The Rockwool Cubes
Peat plugs hold more water than air compared to rockwool cubes, so they aren’t ideal for hydroponic grows.
After examining each method, if you absolutely had to pick one, it would be starter cubes and seedling plugs.
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