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Vapour's Rockwool germination technique

Rockwool is the preferred germination medium when using hydroponics.

Required equipment:

- 2-litre bottle with plastic lid.
- 1" Rockwool cubes.
- Small pointy object about 3mm wide.
- Waterproof tray to hold cubes and liquid.
- 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.
- Tweezers.
- Seeds.
- Thermometer or knowledge of temperature around seeds.


- Vitamin B1
- Sterilisation fluid (Consider using Hydrogen peroxide (H2O2 ) available from chemists. Ensure it's complete removed from all grow surfaces to avoid contamination.

Okay, here we go...

1 - Sterilize everything thats going to be used and ensure there is nothing nearby which may contaminate your environment.

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.

3 - 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 1/2".

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.

5 - 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 mineral water.

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 water. Proven.

- Vitamin B1 ( Brand name: DNA-Cell 1 ). Improves root growth and helps germination. Proven.

- 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 germination.

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.
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  • caregiverken
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great info!
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