Germinating in Rock Wool

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I've never germinated in Rock Wool, don't know the difficulties or tricks of the trade.

A book I'm reading, "Three A Light", suggests using the paper towel method, which I'm familiar with, then transplanting to rock wool. This seems like an extra step, why not plant the seed in the rock wool and save the risk of damaging the sprout.

Anyone use rock wool for germinating? Tips of the trade would be appreciated.

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Used to do it like this when I ran aero-rails. You can germinate using the paper towel method of course but dropping beans directly into cubes skips the delicate step of transferring. What I used to do is first soak the cube in ph adjusted water; a drop or two of lemon juice in a cup of water should bring ph to proper range. Squeeze off gently the excess water and drop in the seed. Place the moistened & seeded rockwool cube into a ziplock baggie and seal it up. Keep in a semi dark space with ambient room temps until sprouts emerge and then you can remove the baggie.

Dont squeeze the rockwool. It fucks with the structure that makes it special. Shake off excess water with a flick of the wrist. Go until the cube is noticeably lighter, 25% to 50% saturated

Use Root Riot plugs. I used rockwool macro plugs and the little square kind for years and they both suck. They are too wet until they are too dry. Root Riot plugs are just easier overall and work great when you transplant into bigger rockwool cubes, coco or whatever the medium is. Plus you can squish them if you want.

lusidghost said:

Use Root Riot plugs. I used rockwool macro plugs and the little square kind for years and they both suck. They are too wet until they are too dry. Root Riot plugs are just easier overall and work great when you transplant into bigger rockwool cubes, coco or whatever the medium is. Plus you can squish them if you want.

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Second the Root Riots. Just transplanted 60 plants started in them. Too easy. Just found an unopened bag of rockwool cubes today. Hope someone can use them.

Why use rockwool when there's better alternatives available? I understand if you're running flood and drain but sprouting seeds in RW and transplanting to soil doesn't make any sense at all. It's a less ideal starting medium compared to peat pucks and coir and on top of that really bad for the environment.

A salad spinner is supposed to be good for getting the water off the cubes, or a flick of the wrist.

Holding it loosely in your hand after soaking it your chosen nutrient solution you use to start seeds or water make the motion you would make as if you were throwing a baseball while still loosely holding onto the cube. It will fling a fair amount of water off so do it into the shower or outside. Done, now plant your seed and water when it feels light.

I agree with the folks suggesting you use something different like root riot or coco for starting seeds, in a jam I'd use rw starter cubes but they'd be my last choice, they're not difficult to work with but the alternatives are better imo, starter cubes need a lot more attention especially with a heated prop drying them daily.

The small volume means they're not in the sweet spot for very long they probably spend more time too wet/dry than ideal.

When I did use them I soaked them then shook off the excess and put the seed in the hole then teased some rw fibres over the hole, when required I used a syringe to feed them.

Eta... I usually soak my seeds but with rw I don't, if they sprout a tap root its a pia trying to put the seed into that small hole and not break it, it's best to put them straight in day #1.

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Thanks for the advice from everyone!

I'll look into the Root Riot plugs, I've been using Rapid Rooters for years, hopefully similiar.

I'll be back when I get more info.

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I personally prefer the paper towel method then rockwool. Partially due to me being DWC, but mainly so i can monitor the seed closer prior to placing it in the RW. I also will split the RW in half and gently place the seed/ roots into it. Then close up and surround with hydroton. I do the same with soil in the rare event i do soil. As mentioned above i also soak the RW first, then lightly grip and flick my wrist, similar to packing some chewing tobacco, for those who know what i mean.

Hobbes said:

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Thanks for the advice from everyone!

I'll look into the Root Riot plugs, I've been using Rapid Rooters for years, hopefully similiar.

I'll be back when I get more info.

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Double check to be absolutely sure but I think root riot, root it and rapid rooters are all near enough the same thing if you have either one there's no need to spend more money.

I have been using rockwool for 10+ years. Best medium in my opinion to start seeds and clones. Plus you don't have to rip it out of the wool to transplant. If you grow dwc hydro it can stay in the block, if you grow soil you can just plant the block. I don't know why so many are against rockwool, but I just give one tiny squeeze so I see a lil water come out the cube and I know it not completely soaked and room for air. They dry fast so that's always been enough for me

I advocate for grodan grow cubes. I see more issues on here from plugs than I ever have rockwool

ProPheT 216 said:

I advocate for grodan grow cubes. I see more issues on here from plugs than I ever have rockwool

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Who is having issues with Root Riot plugs? The only germination issue I ever see is from people putting the seeds in a paper towel.

All germination products have a learning curve. Believe me, I've tried them all.
I used rockwool for a few years and wasted a few seeds before I figured it out. It does hold a lot of water.
Rapid rooter became my go to for seeds and clones. Now I just put a little coir in my soil for the seed to germinate in.

Has anybody ever tried putting a rapid rooter into a rockwool cube?

I mean a big, 4x4 or 6x6 rockwool cube

Tolerance Break said:

Has anybody ever tried putting a rapid rooter into a rockwool cube?

I mean a big, 4x4 or 6x6 rockwool cube

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I use them in 4" cubes, but they all have the same size holes. They are pretty much form fitting and sit much more snug than macro plugs.

lusidghost said:

I use them in 4" cubes, but they all have the same size holes. They are pretty much form fitting and sit much more snug than macro plugs.

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Fuck yeah, ill give them a go next time around.

I dont like mixing grow mediums. Paper towel method for me then into a very light soil mix like pro-mix.