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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! 

  • Contains no harmful chemicals, weeds, diseased soil or pests.
  • Pathogen free.

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 regular cube: 40x25x25mcm, large cubes are 40x40x40mm.

  • Regular size are tapered to fit into netcups
  • Small indents for cuttings and seeds.
  • Can easily be broken up by hand or with a scissor.
  • Available in 24 or 72 packs for better value.

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!

Customer Reviews

Based on 74 reviews
Susan I.
Great product and service

This Rockwool product is great. Easy to use and I'm enjoying being able to propagate my aquarium plants with this fantastic product. Urban Plant Growers provide a great, fast service and delivery

Mary W.
Replace regularly

These rock wool cubes work so well and if replaced each time you replant, they don’t go moudly. Best fit for the UPG trays.

Deborah S.
Best rock cubes on the market

There are many rock cubes out there but Urban Plant Growers cubes are of the highest quality and frankly, all my seeds grow better in these than anything else. Recommend you buy a large pack so save money and time.

Mindy N.
Plants succeed every time!

This has transformed the way I grow seedling, never had a plant fail. I either leave them in the hydroponic bay or remove them with their little rock wool core intact and transfer them successfully to the garden.


Good but tends to go green after a while.