Grodan Rockwool Cubes

Rockwool Cubes For Germination & Propagation

Rockwool cubes are rooting blocks that hold a tremendous amount of water for their size, which provides a buffer against power outages. On average they also hold at least 18% oxygen between the fibres providing a tremendous amount of oxygen to the root zone, as well as making it incredibly difficult to overwater the plants.

These Grodan Rockwool rooting block cubes are ideal for raising seedlings and cuttings. Clean, sheer weight and supplied in their own plastic tray for easy handling, these continue to be one of the most popular growing mediums we sell. Once roots start to emerge through the cubes, you will need to plant them on into larger Grodan Transplanting Cubes or some other medium. There are 2 sizes of cube available: Large Cuttings Seed Cube = 3.6cm (one and a half inch) and Small Cuttings Seed Cube = 2.5cm (one inch)

Uses of Rockwool Cubes

Primarily growers use rockwool cubes as growing media for two main purposes in their hydroponics systems: germinating seeds and propagating new cuttings. Typically the 1.5” cubes are used for starting seeds or propagating cuttings. Some of the larger cubes (up to 4”) are used as a growing medium for compact plants as well, but on a much smaller scale.

How to use Rockwool Cubes

1. Prepare the rockwool cubes for use, making sure to soak them in pH-adjusted water to bring their pH down between 5.5 and 6.5.
2. To Plant Seeds:
• Insert 2 seeds in the hole on the top of the rockwool cube. Use a toothpick or other similar object to press the seeds down to the bottom of the hole.
• Pinch the hole closed.
• Place the cubes in a nursery tray and cover them with a humidity dome to lock in moisture.
• Maintain at 70 – 80°.
• Keep rockwool cubes moist by watering sparingly every couple of days or misting them with a spray bottle when they start to dry out.
• Remove from the humidity dome and place under the sun as soon as seeds sprout.
• Cut the tops off the seed in each cube (if you planted 2 per cube) that isn’t the strongest or tallest. Do not pull them out as it may dislodge the healthier plantlet at the same time.
• Transplant when plantlets reach 2-3” in height.
3. To Propagate Cuttings
• Water the stock plant well the night before beginning the propagation process.
• Remove a 3-4” leaf stem cutting from the main stem of the plant, cutting it off as close to the main stem as possible without damaging the node.
• Dip cut ends in rooting hormone.
• Plant the cutting in the rockwool cube making sure it doesn’t poke out the bottom of the cube.
• Fill a nursery tray part way full with perlite or vermiculite.
• Set rockwool cubes on top of growing media.
• Cover the nursery tray with a humidity dome to lock in moisture.
• Maintain close to 80°.
• Crack humidity dome when roots begin to emerge, gradually increasing the day after.
• Remove the humidity dome a couple of days after roots first appear.
• Transplant when roots begin to poke out the bottom of the cubes.