When would you need a rockwool slab longer than a uni-slab?

Apostatize · Dec 16, 2022

When would you need a rockwool slab longer than a uni-slab?

Currently, I'm stacking a 3" block atop a uni-slab. I realize strain yield varies, so perhaps it's more helpful to focus on plant dimensions that would require more root room than is in a uni-slab. But how tall and wide is that?

J. Rocket · Dec 17, 2022

use a 6" rockwool block. its got 8 times the growing volume of the 3". shouldnt need the slab then.
theres also an 8" block if you need. about 18 times the growing volume of the 3".

Apostatize · Dec 17, 2022

J. Rocket said:
use a 6" rockwool block. its got 8 times the growing volume of the 3". shouldnt need the slab then.
theres also an 8" block if you need. about 18 times the growing volume of the 3".

Yep, 3" instead of a starter plug in a 4". I start clones and seeds in a 3". But that sits atop the uni-slab. Unislab lets you have a lower profile than a 6" or big mama 8". If there's a deal on big mamas, I slice them in half. Believe it or not, a unislab is supposed to support a larger plant than a big mama (or perhaps the ads are misleading). Stacking a 6 or 8 atop a unislab is probably cost prohibitive.

So, I should rephrase: what's the biggest a plant can get on a unislab? At that point, I suppose a 36" long slab is the next step -- I just want to know if I even need to consider a slab larger than a uni.

Apostatize · Dec 17, 2022

Another reason to start in a 3" v. a 6 or 8 is simply so I can propagate more plants in my perpetual bloom setup. It's like an assembly line at this point.

J. Rocket · Dec 18, 2022

if your stacking a 3" on a slab your at least 6" so there goes the lower profile.
cant help on the slab grow size thing.
I go from sprout to hugo to harvest, no need to stack.

Apostatize · Dec 18, 2022

... a 6 atop a slab would be taller and more top-heavy than a 3 on a slab. Ok, I'll wait to see whether anyone who uses slabs has a suggestion. Thanks. and slabs are supposed to support larger plants than a hugo. I'm not shooting for 4 zips.

i anticipate that a uni-slab will be sufficient. But these are eventually going to bloom in a greenhouse/high tunnel and I just want to be informed about what to expect and what the size limitations are. All indoor currently, so it's not a pressing issue.

lusidghost · Dec 18, 2022

Apostatize said:
When would you need a rockwool slab longer than a uni-slab?

Currently, I'm stacking a 3" block atop a uni-slab. I realize strain yield varies, so perhaps it's more helpful to focus on plant dimensions that would require more root room than is in a uni-slab. But how tall and wide is that?

When you're running multiple plants. I grow three per slab, which is still too much RW imo. So I cut about 8" off of a 36" slab.

I would go with a 6" cube over a unislab, and avoid regular slabs. Uni/regular slabs are hard to water evenly unless you take them out of their wrapper and put then into a tray covered in panda film.

Apostatize · Dec 18, 2022

lusidghost said:
When you're running multiple plants. I grow three per slab, which is still too much RW imo. So I cut about 8" off of a 36" slab.

I would go with a 6" cube over a unislab, and avoid regular slabs. Uni/regular slabs are hard to water evenly unless you take them out of their wrapper and put then into a tray covered in panda film.

Thanks. By the time the high tunnel is up, I'd buy these grow bags: https://trimbuddies.com/products/68...HAKx__mdFjjd9YVj-sMyKNfFNRc9rNj3pnkEUXn8n0J4I

Yes, I've seen a video of Dark Horse's owner putting a slab under a big mama; he said it's primarily to give him an extra 4 hrs of moisture (i.e., it's a preventative measure for him). But he also has a huge space to grow in. I hear you on the hugo + slab combo (actually, I read it again and it sounds like you were preferring hugos v. slabs). My main reservation about combining a hugo and uni-slab is simply that I'm able to clone more plants in my limited space using 3" blocks (huge box/case at a time, cheaper than 4" + plug, which I found to be a waste of time/$).

If I recall, was it you who recommended uni-slabs to me a while ago? Since then, I've been buying ~16 uni-slabs at a time, as well as ~12-20 Big Mamas (on sale) and slicing them in half. Perhaps it's just that, after sex determinations, my plants are getting bigger because they have more time to mature, but I've been pretty happy with the uni-slab.

Eventually, my current bloom-dedicated space will be converted to veg the most mature plants ... and when only 4 fit -- or maybe only 2 -- I expect those will return a much greater yield in a greenhouse. But it doesn't sound like I need to go bigger with slabs and that's reassuring.

Thank you, Lusidghost and J. Rocket.

lusidghost · Dec 18, 2022

Apostatize said:
Thanks. By the time the high tunnel is up, I'd buy these grow bags: https://trimbuddies.com/products/68...HAKx__mdFjjd9YVj-sMyKNfFNRc9rNj3pnkEUXn8n0J4I

View attachment 5239228
Yes, I've seen a video of Dark Horse's owner putting a slab under a big mama; he said it's primarily to give him an extra 4 hrs of moisture (i.e., it's a preventative measure for him). But he also has a huge space to grow in. I hear you on the hugo + slab combo (actually, I read it again and it sounds like you were preferring hugos v. slabs). My main reservation about combining a hugo and uni-slab is simply that I'm able to clone more plants in my limited space using 3" blocks (huge box/case at a time, cheaper than 4" + plug, which I found to be a waste of time/$).

If I recall, was it you who recommended uni-slabs to me a while ago? Since then, I've been buying ~16 uni-slabs at a time, as well as ~12-20 Big Mamas (on sale) and slicing them in half. Perhaps it's just that, after sex determinations, my plants are getting bigger because they have more time to mature, but I've been pretty happy with the uni-slab.

Eventually, my current bloom-dedicated space will be converted to veg the most mature plants ... and when only 4 fit -- or maybe only 2 -- I expect those will return a much greater yield in a greenhouse. But it doesn't sound like I need to go bigger with slabs and that's reassuring.

Thank you, Lusidghost and J. Rocket.

I may have recommended the unislabs, but I haven't used them in around 2 years I think.

Yeah, they will definitely hold water a lot longer. If you're only watering once a day, then throwing a slab under will help. I'm watering 10 times a day and want as much dryback as possible between. Which is why I'm switching from slabs to RW chunks.

Apostatize · Dec 18, 2022

Just one more detail. Yes, uni-slabs aren't easy to water. Under the 3" cube, I cut a square in the uni-slab wrapper large enough for the square green plastic hugo block covers I don't use anymore since I stopped buying hugos. Otherwise, it would be really wasteful/messy feeding drain-to-waste once a day.

lusidghost · Dec 18, 2022

Apostatize said:
Just one more detail. Yes, uni-slabs aren't easy to water. Under the 3" cube, I cut a square in the uni-slab wrapper large enough for the square green plastic hugo block covers I don't use anymore since I stopped buying hugos. Otherwise, it would be really wasteful/messy feeding drain-to-waste once a day.

That's a good idea. When I fed them through the plant's 4" cube and took the wrapper off after the harvest, the upper outer area still looked brand new with no roots at all. The unislabs aren't as dense as the cubes / regular slabs and didn't seem to wick as well.

When would you need a rockwool slab longer than a uni-slab?

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