Rockwool Starter cubes - 25mm Rockwool Starter cubes - 25mm
Once the roots start to emerge through the bottom of the cubes they can be transplanted into a larger rockwool cube or any other medium. As these cubes are smaller, than the 36mm cube, roots appear faster and can be quickly potted up. The 25mm cube trays contain 150 starter blocks, nearly twice the number you get in the 36mm trays.

Below is a guide to rockwool covering:

1) General note about rockwool
2) Good for beginners?
3) Preparation
4) Tip
5) Storage
6) Warning

1) General note about rockwool

Like an artist with a blank canvas rockwool cubes offer the grower an inert, sterile platform from which to work your magic. Cubes are supplied in trays that can be easily cut with scissors, so if you only need to use part of your tray you can cut the tray as required, saving the remaining part tray for a later date.

2) Good for beginners?

Experience has told us that sometimes beginners struggle with rockwool to achieve the ‘taking rate’ they’d desire using rockwool cubes. However once you’ve got the hang of them you won’t look back. Rockwool is used as loft insulation due to its ability to hold air. Horticultural grade rockwool is refined but used for exactly the same reason –
its ability to hold air. If you wish to produce lots of seedlings or cuttings for hydroponic production they are the one.

3) Preparation

If you are just doing a moderate number of cubes there is an easy way to prepare your cubes.

1: Fill a sink with water,
2: Get the acidity level correct: add a couple of drops of pH down acid and test the pH, repeat until the water has a pH of 5.5-6.0,
3: Throw in the cubes to soak.
4: Leave overnight and
5: Drain in the morning.
6: Gently shake and squeeze each cube to remove excess water.

Now the cube is ready to accept your seed or cutting.

Some growers, using tap water, choose to leave the water they use to soak cubes for a day before use, allowing the chlorine in the water to escape.

4) Tip

Some growers like to add a little something to the water that the cubes are soaked in – just to help the new seeds or cuttings on their way e.g. Nitrozyme or Superthrive

5) Storage

Rockwool cubes arrive dry and provided they are stored in dry conditions will last indefinitely. Before use they need soaking in pH adjusted water, preferably overnight.

6) Warning

Rockwool is itchy, it contains fibreglass! Handle with care avoiding throwing the dust into the air you are breathing. A simple water sprayer can be handy to keep particles from been thrown into the air when handling trays and cubes.