Rockwool is the preferred germination
medium when using hydroponics.
- 2-litre bottle with plastic
- 1" Rockwool cubes.
- Small pointy object
about 3mm wide.
- Waterproof tray to hold cubes and
- Water. (We will come back to the type of
water.) Allow tap water to stand for 48 hours before use
if you have to use tap water.
- PH Test kit.
Phosphoric Acid. Or PH UP/Down.
- Thermometer or knowledge of temperature
- Sterilisation fluid (Consider using Hydrogen
peroxide (H2O2 ) available from chemists. Ensure it's
complete removed from all grow surfaces to avoid
Okay, here we go...
1 - Sterilize everything thats going to be used
and ensure there is nothing nearby which may contaminate
2 - Place the 1" cubes in the
tray you will be using to germinate your seeds. Ensure
they remain stable while you work on them.
Take the 'pointy object' (pencils/pens are a bad idea,
use a clean nail or knitting needle) and open the
pre-made holes in the Rockwool cubes to ensure the seeds
will fit. Snugly place at a depth of between 1/4" and
4 - Using the tweezers place the seeds
into the rockwool cubes. There are many schools of
thought on the depth that provides the best results.
1/4" is generally accepted as good but some prefer
slightly deeper. Consider this, the seed only carries a
certain amount of 'fuel', so placing too deep may cause
the seed to fail in it's attempt to break the surface of
the cube. Orientation is also a factor. Good seeds are
always pretty regular in their shape. For best results
place the seed with either the crack or the 'pointy end'
down. This allows the seed to use minimal energy
orienting itself and also reduces the risk of the
seedcase becoming stuck while trying to push free. You
should now have a neatly laid out tray with a number of
Rockwool cubes each containing a single seed.
- Next we will need to mix up a batch of water. Seeds
will 'pop' with just water from the tap but this does
reduce the rate at which they germinate and the quality
of the seedlings produced. To help the seeds in the
beginning of their journey, you will need to ensure they
have everything they need to begin with. Start by
obtaining the water and noting the PH value. Below, are
the recommended types of water.
A - Distilled.
B - Mineral. (Check content before using. Some
bottled/mineral water contains high salt levels. Always
check contents are compatible and within safe limits. )
C - Boiled and filtered.
D - Bottled water. See
Ensure you have enough supply for
up to 10 days watering. Now we can add a few items to
further help them. The following is a list of optional
additions that can be used. Not all are agreed to help,
but I will detail this next to the item.
Bleach or H2O2 ( Note: bleach is poisonous to plants, be
sure to use little-- try to use a different solution if
possible. H2O2 is a good choice and also helps oxygenate
the water. ). This helps remove the possibility of
fungal attack and helps keep water free of bacterial
invasion especially recommended when using distilled
- Vitamin B1 ( Brand name:
DNA-Cell 1 ). Improves root growth and helps
- Superthrive. Contains
trace elements. Also used in vegetative growth to give a
boost to your plants. No conclusive evidence known
regarding effectiveness in germination, however, this
product is worth having in your arsenal while in veg
growth. Do not use while flowering! Note that
Superthrive contains Vitamin B1 and can be used in place
of B1 alone. I use only vitamin B1 and Distilled water.
I have found this to be a good germination solution and
consistently get between 80-100% germination. Once you
are happy with your solution you need to measure the PH.
You will notice the PH has probably changed slightly if
you added anything to the original water. Ph should
measure between 5.8 and 6.5 with around 6.2 being
optimal. Should you need to change the PH use the PH
Up/Down. Most tap water will only require PH Down, as
the water is usually Neutral or thereabouts. Once you
have achieved the correct PH you are ready to continue.
6 - Next step-- which is often missed-- is to
ensure the germination environment is suitable. The
seeds will not require light until they have shown
through the top of the cubes and the 2 leaves have
opened but it is always a good idea to have the light
set-up. Gravity is used to orient the seed and ensure it
knows which way to start pointing! Fluorescent light is
the best at this stage and under no circumstances use a
HID lamp. The seedlings will not be strong enough to
cope with a HID lamp until at least week 2. Once
lighting is set-up you need to ensure a stable
temperature. 24 Degrees C is the best temperature for
7 - Now you are nearly finished and
just need to moisten the Rockwool cubes. Using the
2litre bottle cut a small hole in the lid to allow the
water to trickle out but not flood freely. Water the
rockwool evenly until you see water appear at the root
of the cube. Continue until all cubes are watered. Now
remove any standing water at the bottom of your tray.
The seeds will take between 24 hours and 10 days to show
through the cubes, with around 3-5 days being the norm.
You MUST ensure that during this time the cubes maintain
a damp but not wet state. Allowing the cubes to dry out
will kill the young seedlings.
You may over time
make changes to this system, but if youre a first timer
this growFAQ will give you a good start. Best of luck.