There's no easy way to say this, so I'm just gonna put it out there: most growers
are rushing the propagation stage. That is, the first few weeks of a plant's life,
and hurrying their plants into hydroponic systems. However, amigos, if you
keep your cool, and don't rush your plants through these key early stages, I
promise that they will deliver far bigger yields further down the line. If
you're growing hydroponically and haven't tried stonewool cubes and
blocks yet, what's wrong with you? Just kidding. They're hard to beat, especially
for the propagation stage. Stonewool is clean, consistent, easy to use, and ideal
for creating homogenous batches of healthy plants for all types of
hydroponic techniques. Yes you do have to pre-soak stone wool before use. The
one-step approach is to use a mild vegetative hydroponic nutrient solution
at around pH 5.5 to 5.8, and let the stonewool soak for between 1 and 15 minutes.
The larger the blocks are, longer the soak time. Now, some growers prefer a
two-step approach: firstly soak in a pH 5.5 water, then they perform a second
soak in a mild nutrient solution. Now, this two-step approach will arguably
provide more pH stability in the stonewool, as pure water will remove any
residual lime more effectively. Be sure to allow the blocks a chance to fully
drain before use. I like to shake out some of the excess solution, rather than
squeezing it, as it's too easy to compact the stone wool fibers, and damage
the micro pores which the roots love so much. Now, when growing like this, always
start seedlings and cuttings in a propagator.
Once you see a root or a few pairs of true leaves, it's time to wean them off
the warm and humid environment inside the propagator, and prepare them for the
real world of your bedroom. We call this process "hardening off." Open the vents in
the lid, then move on to leaving it at a slight angle to allow more airflow, and
to slowly reduce the relative humidity and temperature inside the propagator.
After a few days the lid can be removed completely and the plants will have
become more acclimated to their new environment. For young, vegetative plants
I aim to keep daytime temperatures between 73 and 79 degrees Fahrenheit.
That's 23 to 26 degrees Celsius, for you sensible metric people, and lights on for
18 hours a day. Some growers choose a 24 hour cycle, as it's easier to maintain
consistent temperatures, but your plants will thank you for the short rest. The
ideal relative humidity for juvenile plants is between 65 to 75%. This
promotes a lower transpiration rate, which in turn will allow your young
plants to concentrate their energy on root and leaf growth. Most growers use T5
fluorescent lighting, or LED lighting at this stage; although, an LEC 315 is also
great option. As far as irrigation is concerned, follow the 50% rule. Young
plants are very sensitive to both overly wet and dry conditions.
Don't robotically dip your cubes every day, or leave them standing in water. Wait
until they dried out at least by half before redipping. Stonewool feels
very light when it's dry, and often looks lighter in color. If you take just one
thing away from this, it's the importance of air-pruning young plants. I'm not
necessarily talking about fabric pots, or specialist air-pruning pots, either. Air-
pruning is a really simple technique that stops root growth from extending
beyond it's growing media by exposing the roots to relatively dry air. When
propagating with stonewool blocks, the plants' first primary roots will grow down
through the block until the tips grow out the bottom. Once the primary root tips
are exposed to the relatively dry air, they will stop growing and die back. I
know how that sounds, but it's actually a good thing. As these primary roots now
have nowhere else to grow, it stimulates an abundance of secondary roots to
branch out from them, and these secondary roots will then spread through the block
until they to get air-pruned and stimulate yet more root branching. The
overall effect of this growth and pruning cycle will create a plant with a
well-developed root system throughout the entire block. Air-prune plants will
literally explode with root growth when they are transplanted into their final
hydroponic system. In practice, all that's involved with air-pruning is setting
your blocks up off the grow tray so that air can circulate beneath. Grodan makes
an awesome Grow Smart tray, specifically for this purpose. It can accommodate both
the A-OK starter plugs and larger blocks, but you can fashion something yourself
by using a wire mesh, or appropriating a rack from your oven. The key is getting
air circulating beneath the blocks. This concentrates and contains the roots
within the propagation media itself, forcing the roots to explode every nook
and cranny available to them. A lot of growers mistakenly believe that the
first sign of roots out of the bottom of the block is thier que to move on to the
next stage, and actually that's the last thing you want to do. All this will do is
produce plants with a few long roots coming through empty stonewool blocks.
They'll also be more likely to be set back when planted, as the lack of root
mass within the block will not be able to cope with the frequent irrigations,
and large volume of water held by the block. Inevitably,
this will cause the plants' health and growth rate to suffer through over
watering. This scenario is very common with growers using the nutrient film
technique, or NFT. Don't rush those plants into the NFT system! The aim of the game
is to create a bunch of plants with an abundance
of roots filling the internal structure of the stonewool block before
planting them out. And this, amigos, is what air pruning is all about. Thanks for
watching, and please don't forget to subscribe.
This is Everest, out.