Some indoor growers are... how can I put this? [BASH! BASH! BASH! BASH!] Intimidated by stonewool slabs. I dunno ... maybe it's the silver wrapping: it kinda looks all
super professional and scientific over your standard bag of potting mix perhaps.
As for me, I've had a love affair with stone slabs for many years now, so I
thought it was high time that I made a short video with everything you need to
know to give them a try.
Here we go! First thing I love about gro-slabs: there are no pots to fill ... ever! You just start your
seedlings and cuttings in A-OK starter cubes, transplant, then when you're ready,
in to three or four inch Delta blocks, and when you have a bunch of roots coming
out of the bottom it's time to move them onto their final destination: a Gro-Slab.
Now, I'm using three-foot long Grodan Gro-Slabs - 360 ounces
of stonewool. You can also get double width slabs 12 inches wide at
720 ounces. Now, you might be thinking that 360
ounces is not a whole lot of growing media, but that's where you'd be
wrong.
Stonewool slabs are the commercial growers go-to when it comes to growing monster
plants. They can support major production. In fact, it's not uncommon to see 2 or
3 14-foot-high tomato plants growing out of just one of these in a
commercial greenhouse. Here, in my grow room, however, I prefer squatter, more
compact plants, so I'm going to use 4 of these slabs to grow 16 bushy little chili
plants. I planted, count them: 1, 2, 3 varieties. Cheyenne, Prairie Fire, and
Purple Tiger. Now, it turns out that my Purple Tiger isn't actually Purple Tiger
because the seed company claims they made a mistake and put Purple Prince in
the wrong packet, but that's another story-- and a big thank you to my facebook
friend Rob Maxfield for spotting it had the wrong leaf shape! Anyway, under
grow lights, you can easily grow 3 or 4 compact-size plants in a single
Gro-Slab. As always when growing indoors, be sure not to veg (grow) your plants up too long,
otherwise you'll soon have an impenetrable jungle on your hands, which
is difficult to illuminate efficiently using just grow lights. I'm using soft
mesh netting to spread out the canopy. An important tip when growing light-loving,
flowering plants indoors. Alright, let's talk prep (preparation). Like all stonewool products,
Gro-Slabs need to be pre-soaked. If this sounds like an onerous task, then
listen up: it's worth it for the end result. First, do not remove the UV
resistant packaging-- ever-- as it helps to protect roots, and keep your slabs moist,
and algae free. The plastic wrap stays on right through harvest time. On the top
side (look for the arrow) cut some X's at each plant site. You'll want them just big
enough so that you can fold the flaps up and insert your Delta block snugly into
place later. Okay, don't cut the drainage slits at the bottom just yet.
The next step is to fill up the entire bag with your pre-soak solution. I'm using
90% reverse osmosis and 10% tap water pH adjusted to 5.5. You can use just tap
water if you like, but it must be pH adjusted. You can tell the slab is full
when the sides start to bulge out. Now, let the slab chill like this for at
least a half an hour, and then carefully I say carefully, flip it over to one of
its sides-- it'll be heavy-- and cut some drainage slits. Ideally, the slice should go
from the bottom, up the side, just a little bit, and evenly spaced between the
planting sites on the other side. Now, put some at the ends of your slabs, too.
Carefully transfer the slabs into a purpose-made grow tray (aka leach tray) like this.
They're designed for the job. I pour around 4 cups of a mild nutrient
solution into each plant site. Now, some growers prefer to recirculate nutrient
solution through the slab with drippers for a few hours for more balanced
nutrient distribution throughout the slab. Whichever method you use, it should
be the same strength that your plants are already used to. In this case, around 600
ppm, or 1.2 milisiemens, pH 5.5. Then take each plant and sit it on the slab.
Ensure that the Delta block is moist, otherwise remoisten it with nutrient
solution, and that's it!
Well, that's it for 4 to 5 days. Don't re-irrigate during this time, as it encourages
the roots to venture into the slab. And then, after the fourth or fifth day of the
rooting period, I manually top feed with around 4 cups of nutrient solution
per plant-- that's about liter once or twice a day. I could hook it up to a dripper system
straight away, but there's something quite Zen-like about starting off
manually, plus you get more of a feel for your plants. As for automation, top
feeding with one dripper per plant is my recommendation; ebb and flow makes the slabs
too wet. I use one dripper stake per plant, inserted into the Delta block,
irrigating through the top block and not directly into the slab. It's always
preferable, as new roots are always formed at the base of the plant in the
Delta block itself, and as you can see I use a small piece of wood to create a
slight gradient to aid drainage. This really isn't strictly necessary, but it's
something I like to do. If you're looking to use stonewool slabs in a vertical growing
system, then choose something
like the ParGro V-Slab, as it has denser wool for improved lateral distribution. Run off
should be approximately 20 to 30% of the volume of the nutrient solution
that you deliver. Now, check out my other video on DIY dripper systems for more
information.
You should periodically compare the concentration and pH of your run off
with your feed solution. I'll talk about this and more in a follow-up video, but
as always, please, please, please hit me up with any questions in the comments, and a
big, big, big, big thank you to all of you beautiful people who have subscribed
already. It's free after all, and a simple click on that enticing red button
is like an automatic dose of serotonin shot directly into my brain. I mean, it's
just a shame you can only subscribe once because I know some of you would just be
sitting there all day pressing my joy button-- hey ho! Thanks for listening,
bye for now! This is Everest, out.