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.
If you’re growing a photoperiod plant, you’ll need to switch your light cycle to 12 hours on and 12 hours off to force them to flower. If you’re growing outdoors, nature will take care of this for you. Keep autoflowering varieties on a light cycle of 18 hours on and 6 hours off if growing indoors.
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.
Rockwool makes germinating cannabis seeds super easy. Moreover, it works well for hydroponic growers who want to use cuttings.
Before you pop your seeds into the cubes, you’ll need to adjust the cubes’ pH to make them less alkaline. This step also gives you a chance to infuse nutrients into your cubes to give your seedlings the best start to life possible.
Overwatering kills many grows before they even get started. Damp conditions can foster fungal pathogens that quickly destroy seedlings. Although Rockwool cubes are largely safe from microbes, excess water can still suffocate roots and hamper growth. Good aeration stops this from happening.
They should look like this:
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.
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.
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.
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.
Take 1-2 seeds and insert them carefully into the holes. Use a toothpick or similar object to push them down to the bottom, as you want them to be at the bottom of that hole. Rip or push a piece of the Rockwool over the hole (you don’t have to fill it completely), so that the seed can germinate in a dark moist environment.
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.
Check out this method in action:
This gives you the advantages of each method, with the least downside of each.
But the best way to germinate weed seeds would really be a combination of these methods.
Why does this work?
Not all of these methods have the same success rate, and your precious cannabis seeds are expensive to buy.
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.
This method is not so much a way to fully germinate your seeds, but rather ensures rapid and reliable germination.
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