Help with rockwool

Hey! Starting a grow using rockwool cubes but i could only find 4" cubes. So I am wondering if i can start my seedlings off in these 4" cubes and if not can i cut up the 4" cubes in 1" cubes and use them like that?

Yes... you can no worries

yes i can start off in the 4" or cut them up?

I would not start a seed in rockwool personally. You will find greater success by starting the seed remotely, and then transplanting into the rockwool. Yes you can chop rockwool into what ever you need. Make sure you PH to 5.4 f you use rockwool, or you will kill your seedling, or severely stunt it. Good luck

4" rockwool cube

are ph strips good enough until i get a digital ph meter?

are ph strips good enough until i get a digital ph meter? ...again yes, but be cautious, germ the seed in a kitchen towel/dish and keep warm, then to the damp rockwall, but to size first tho!

Cut it in 4- I use half cubes all the time

thx peeps. hopin this goes well

anyone know much about watering them in the 1" cubes? Plain water for a bit? 1/4 nutrient water ? how much and how often? looked around can seem to find a good answer about watering! \Keep the bottom half wet is something else i read? And do i do everything the same when i put them in the 4" cubes?

Chop one cube up in tiny pieces and fill the holes in the larger cubes and use a toothpick to make a hole to shove the seed down root pointing down. Only needs to be about 1/4-1/2" under. Keep the center moist to the touch and put it in a dark space until seeds have popped the surface. Plenty of moisture is a good thing as rock wool provides enough air for seedlings even when wet. I dont use any nutes on my babes until their first real leaves pop. Use 1/4 strength nutes once the first veg leaf appears and continue that until its time to transplant into containers.

Its more beneficial to use no nutes and have a correct ph range with seedlings. They have a lot of energy stored in them already and adding nutes only hastens things a bit.


If you soaked your cubes in ph adjusted water for 24 hours @ 5.5 you can water at 5.3-5.6 ph. If you did not leach your cubes it will need to be slightly lower (4.8-5.2) because it will raise the ph of the medium over about a 12 hour span.




As for germination, there are many right ways and a few wrong ways. I personally dont like the paper towel method as I've had seeds dry out on me... I would highly recommend leveling a cup with a few oz. Of water in it and simply drop your beans into it. They will float until they have germed then will sink to the bottom. I leave them in the bottom of the water until they have 1/4"+ roots then do my transplanting. 100% success rate and the least amount of attention needed.



Hope this helped

yes great help thx

I agree with hydro- rooting out in rockwool has several benefits including ez transplanting and ez flushing later on if needed. You will need to ph down your water- I ph down to 5.8 or 6 & pour it into a spray bottle-then just give it spritz once a day- in the first week or so you can help them root out by adding humidity: put your cubes in solo cups after they sprout & cover with a sandwich baggie as a mini greenhouse

A germination *tip* that helped me: use a salad spinner to spin off excess water just before germinating & put the seeded cubes into a ziplock bag- marinating bags work awesome for this because they have a flat bottom that allows the cubes to sit upright- blow in some air to form a pillow & store at room temp or slightly higher in a dark place for 3-5 days- works every time 100% success rate so far germinating in rockwool this way

the small rockwool cubes seem to be dry out quickly. like they need water every 12 hrs is this right?