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Rockwool Cubes

Number of Cubes

What would happen if you heated up basalt (a naturally occuring volcanic rock) to the point where it becomes liquid and decided to spin it like fairy floss? You would end up with an awesome hydroponic soilless substrate! These rockwool cubes are exactly that, with the outcome being a super light, and absorbant hydroponic growing substrate that maintains perfect aeration and moisture levels at all stages of plant growth.


Rockwool is the ideal growth medium for germinating most types of seeds, propagating cuttings or even growing transplants. High success rates mean you spend less time struggling and more time growing!

These mats are made by Grodan - the market leader in rockwool.  The substrates from Grodan are the only stone wool growing media awarded an EU Ecolabel



Dimensions of each cube: 4cm (h) x 2cm (w) x 2cm (l)

  • Tapered cubes to fit into netcups
  • Small indents for cuttings and seeds.
  • Can easily be broken up by hand or with a scissor.
  • Available in 12, 36 or 72 packs for better value.
  • When basalt is turned into rockwool, it multiplies in volume by 68x, making it incredibly resource efficient.
  • Contains no harmful chemicals, weeds, diseased soil or pests.
  • Pathogen free.

Compatible products

You can use them in a range of Urban Plant Growers products including:

We've got an awesome blog post on hydroponic growth mediums that might help you learn more!


How to use rockwool cubes

To use these simply soak them in water for 10 minutes before planting two or three seeds (its always good to have a backup) per rockwool cube. The cubes can be partially submerged in water, or bottom irrigated with a trickle of water to keep them moist. Note that they don't need much water as they're super absorbent!

When the roots start to grow out of the cubes, then you can place the cubes within another growth medium, soil, or directly in water and let them grow!