January's the time I sow the seeds of my main crops which are tomatoes, chillies, peppers and cucumbers. For propagating my seedlings I use Grodan Rockwool cubes and 'Fleximix'.
'Fleximix' is a peat/pine bark based spongy cube bound together using a plant based polymer. It has a great air to water ratio suitable for seeds and cuttings. These cubes are taken straight out the bag, put into small trays and wet using a spray gun. They come slightly damp but often need a bit more wetting. You can squeeze off any excess water applied as they easily spring back to shape. They already contain some plant nutrients so do not apply any more at this point.
Rockwool cubes are made from heating up volcanic rock into liquid and spinning it like candy floss into blocks. These are then cut into shape. Rockwool contains no nutrients for plants so needs pre-soaking in a mild nutrient solution. I use 'Vita Link' Plant Start at the recommended dose which is high in all the nutrients young plants need. I also use a liquid formula of beneficial microbes , fungi and bacteria called 'Bio Link Plus'. This stuff smells so bad but is great at producing a great root system.
Rockwool should be soaked for at least a few hours but overnight is preferable. Rockwool is also slightly alkaline so before soaking check the soaking solution is around pH 5.5 (near the lower limit which plants can tolerate). I find after mixing the 'Plant start' and 'Bio Link Plus' the pH falls around 5.5 so no further adjusting is necessary. After a few hours the pH of the solution will raise up to between 5.8-6.0 which is considered optimal for plants grown in hydroponics. When I take the cubes out of their soak I give them a few shakes to get rid of any excess solution. Saturated rockwool can hinder germination and welcome diseases. Another way to remove the excess is to lightly squeeze the cubes but I find this can disrupt and compress the structure of rockwool so prefer to shake them.
After the propagation cubes are prepared I write all my labels and make small holes 1 or 2 cm deep for planting the seeds into. Once the seeds are planted into the holes I lightly close them back up to keep the seeds dark. When using fleximix I fill the pre made holes using some fine compost, coco coir or loose bits of fleximix.
Once all the seeds are sown and the trays are labelled I place them in a large propagator heated using a Thermostatically controlled heating mat. On the base of the tray I use dampened Vermiculite or Perlite which spreads the heat evenly in tray and holds water to keep the propagator humid. Seeds germinate quickly in a heated propagator which is essential if your growing area is a bit cold. I try to manitain the propagator around 24c and above 85% Relative Humidity. I find this gives me good results especially for chillies and peppers. Hanging above the propagator is a 110w fluorescent twin lamp (2 x 55w bulbs) which doesn't use loads of electricity and brings on the seedlings extremely well once they pop up.
Once the lid is closed the humidity soon builds up inside. Now all I can do is wait and see. Hopefully in 1-2 weeks I'll be ready to transplant them!
The seedlings have been in the propagator for 2 weeks and have established well into their propagation cubes. Now they are ready for planting into larger rockwool blocks, jiffy coco coir blocks or pots.
I usually decide to transplant the seedlings when the first 'true' leaves are through (after the first 2 round dicotyledons) and/or the propagation cube has roots growing out of it. Notice how the roots growing out of this rockwool cube are very white and healthy.
The plants final hydroponic system usually determines what they are transplanted into. I mainly use 4 inch rockwool blocks which are the most flexible choice as they are suited to nearly all systems. The picture shows the transplant blocks prior to soaking.
The Jiffy coco coir blocks allready contain nutrient so only need to be soaked in water although a root stimulator can be used. After soaking squeeze off the excess solution that the coir will hold.
