Propagating Seeds: Pre-soaking

1. Get two sheets of paper towel and dampen until almost wet, using tap or mineral water.
2. Place your seeds between the dampened sheets of paper towel.
3. Place the sheets of paper towel with seeds between two plates, make sure you get a tight join between the plates so as not to lose humidity.
4. Check daily to ensure the paper towels never dry out.
5. In 1-4 days the seeds should have sprouted a taproot, the pre-sprouted seed can then be planted into a growing medium.

One of the drawbacks of the pre-soaking method is seedlings can suffer transplant shock, also taproots can be damaged when removing from the paper towels. However, this method works good for stubborn seeds that refuse to pop in a rockwool substrate.

Horticultural Rockwool

The rockwool method is recommended when germinating seeds for hydroponic growing systems. The process is made simple using a digital CF meter and a digital ph meter. The CF meter measures the conductivity factor of dissolved salts in the water, a yardstick by which to measure how weak or strong your nutrient mix is. The pH meter measures the pH levels of your water and nutrient mix. Maintaining the right pH levels for your plants is vital.

Begin by making a nutrient solution for the rockwool using a normal 2-pack (A+B) of hydroponics nutrients, measure for one quarter of the strength given in the instructions on the bottle. Example: If nutrients are stated to be diluted at 20 ml of A and 20 ml of B per 5 litres of water, for quarter strength it would be 5 ml of nutrient mix per 5 litres of water.

Use a digital CF meter to test the strength of your nutrient solution. A low CF value of between 8-12 is recommended when germinating and raising seeds. If the CF level is too high dilute with water, likewise if it is too low add equal amounts of A+B solutions until you reach the right levels. Nutrient solutions take time to fully dissolve into the water, so let it sit a while before taking a reading or adjusting the strength.

It is important to get the CF level right before attending to the pH levels as one affects the other, plus you will avoid a potential time consuming mess that could adversely affect your plants. pH down is usually phosphoric acid and pH up is usually potassium hydroxide. You can also get pH down products that are a blend of nitric based acids, which claim to be a more food friendly acid that will not damage food chains such as iron, zinc and calcium. If normal pH up and down are used correctly the plants will benefit from the process of having the pH maintained. Rockwool is slightly alkaline so you need to make the pH solution more acidic to counteract the consistency of the rockwool.

The ideal pH level for rockwool to be soaked in is approximately 5.5. By reducing your pH level to 5.5 you are creating a neutral environment inside the rockwool with the low pH counteracting the naturally high pH of the rockwool. Be careful when balancing the pH, add a tiny amount at a time. If your meter reads high add pH down and pH up if too low. Never mix pH up and pH down together as a concentrate as they react violently to each other. If you mix way too much pH up or down throw away the solution and start again as too much will attack your nutrient solution. Mix your solution well and allow time for it to fully dissolve before taking a reading.

When your solution has been buffered with the right level of nutrient and balanced at the right pH level soak 1 rockwool cubes overnight.

Squeeze about 10% of the water out of the rockwool cubes by making quick downward motions with one hand while holding the block in your other hand. Rockwool holds water like a sponge, removing the excess water ensures the rockwool has enough air inside the block to support the seeds in life, and to avoid drowning the seedlings.

Using a toothpick make a hole about 5 mm beneath the surface. Pick up a seed with a tweezers and place in the hole. Gently cover the hole with the rockwool to close it over, but not too tightly as the seed needs all its energy to pop and break through the surface. Gently cocoon the seed to create maximum humidity and darkness.

The seed can take from 12 hours to 12 days to germinate depending on environmental conditions, the quality and age of the seed. Seedlings require low to medium light levels, two T5 propagation lights will provide the right colour spectrum, blue, for the seedling and vegetative growth phases. Keep the temperature of the environment at about 23 C with a humidity level at 70-90%.

For best results germinate your seeds inside a propagator. The air vents on the top of the propagator enable you to control the humidity levels. For the first week keep them shut, maximising humidity will assist the seedlings to germinate with a minimum amount of trauma.

When the seed begins to grow leaves gently open the vents a slight fraction. As the seeds acclimatise to the lowered humidity level open another fraction, again allow the seedling to adjust before opening fully.

When you can see the roots poking through the 1 cube it is time to transplant the seedling into a 3 rockwool cube. Prepare the rockwool cubes as you did following the same procedure you used to prepare the 1 cubes. As the plant grows into the 3 cube it is time to harden off and transplant into your hydroponics system.