Hey all. Looking for some general advice regarding rockwool cubes for seeds/seedlings. Not just for MJ, but just in growing overall. I had been using soil in seedling trays for garden stuff for a long time. Usually had a pretty good success rate, about 80% +. Nothing too hard about it. Just decent soil, good humidity inside trays with domes, heat mat for seeds and early seedlings, lots of light. After a bit, start gradual hardening off for a week or two, transplant into final destination. Decided to try rockwool because of all the rave reviews. Bought some cheap 1.5x1.5 inch ones and gave it a whirl. Nothing grew. Did some reasearch, bought some better Growdan rockwool, soaked 48 hours in PH balanced waters, only about 50% sprouted and it seemed to take a lot longer for them to grow large enough to transplant. More research, added just the smallest amounts of seedlings nutrients in PH balanced water, still only achieved about 60% grow rate. And still a long time to get big enough for transplant. Did a side by side with soil vs rockwool. Same seeds, same water and nutrients (super minimal), same heat mat, lights, etc. Soil was ready in about 2 weeks, rockwool was about 4 before size and roots were ready. I ended up switching to General Hydroponics Rapid Rooters because of not needing to PH balance, but still only achieve about 75% success at my best efforts. Soil is almost 80-85%. Is there anything you can think of that I might be doing wrong or is it just the way it goes for some growers? I scratch my head about it because it’s so puzzling. I’ve done a ton of research now and can’t figure it out. I’ll plant 5 MJ seeds with hope for 4 to be viable in the RR for hydro. But I could just not crack the rockwool thing to a satisfactory germination rate. Especially at the price point of premium seeds. Any thoughts, advice, sage words that anyone might be willing to impart? Thanks in advance for your help. Have a great day.
Ive been using the coco pods with no issues.
morning Darran… I only use rockwool since I moved from dirt to hydro…one thing I believe about todays seeds is that most are not fresh and may not have been kept properly… the rockwool will dry out fast so you really need to keep dumping water in it… the extra water will drip out if you have it set up correctly and proper moisture will be maintained for germination…
I’ve started doing seeds that have taproots and clones the same. I soak my coco or Promix ina light nute solution with cal mag added at 200 ppm, then drain well. Then, I fill 6oz clear cups with it and plant sprouted seeds to just under the surface and clones dipped in aloe or honey are pushed in to within a half inch of cup bottom. Then into a propagator with a dome until I see roots run down the cup sides. When roots come out bottom transfer to bigger pot. So much easier and better results than rockwool. I like easy……
I have only used rockwool cubes for cutting clones.
I’m definitely into easy, which is what I thought the rockwool would be. I stii want to use it for my hydro stuff, but switched to GH Rapid Rooters because of the difficulties. Anything going into soil or the garden I’m going back to soil starter mix.
If I can ask, how do you prep your rockwool? Any specific brand, type, or size? My first foray, I didn’t realize that I needed to PH adjust first and lost every seed I put in it. That was definitely my fault. But after closely following all the instructions, I still don’t get as good of a germination/seedling rate as I should or do with other grow mediums.
@Retiredoldguy
Hey @SausageMahoney , which peat pods do you use? Any specific prep instructions? Thanks for sharing any info.
You bet brother. Theyre Legigo 30mm 100p peat pucks on Amazon. 10$ for 100. I literally went from killing every seed (19/20) to not kiling them (7/8). I was overwatering.
New process
- Soak for 18-24 hours any water (I’ve been doing Jack’s 321 full strength)
- Soak pods in same water and put in tray
- Put seeds (open or not) about 1/4 in soaked pod and cover lightly
- DO NOT WATER
- STILL DO NOT WATER
- Will spray lid of tray for a week or so, allow 1 or 2 nodes to develop, move to forever home
dry pod
4 Purple Kush soaked 5.18(2 already popped)
Base of GSCX started in pod.
Sorry, that was long but I’m ecstatic I’m no longer “Where the Seeds Go to Die”
I have always used rockwoll … but… I don’t germinate in it . They don’t seem to like it very much , once popped with a tap root they thrive . Hope this helps . Peace .
That’s me 
I use the small 1 1/2" ones.
I just dunk them in water til soaked.
Put clone in cube and place them on a small tray of dirt under 24 hr light.
Yeah ran out of rockwool cubes and used jiffy pods with 100% success so that works too . I might go with the pods next time and keep the cubes for cloning which works very well for me at least .
Thanks @SausageMahoney . I went ahead and ordered a 50 pack from Amazon to try them out. Was only 6 bucks. I’ll see how they do. Still have plenty of other garden stuff to plant. With the grow-off happening, I’m already way over my limit of marijuana plants. I’m already getting terrified about how bad trim jail will be if even half of my plants get to maturity. Last October, I had to trash over 2 pounds worth into composter because I literally could not process it fast enough before it started going bad. Still ended up with 3.5 pounds dry weight.
Thanks for the input. I’m using GH Rapid Rooters now, but they are kinda pricey, about $18 bucks a package for 25. I’ve ordered 50 peat plugs to try. I appreciate your response
No PH balance or ?
Trim bowl!!! There should be song about it.
Just received mine today 
Maybe give it a whirl tonight
And very much agree 
I agree!