Grodan Gro-Blocks are 1.5-inch square rockwool starter cubes for germinating seeds and rooting cuttings before transplant. The Improved version uses a denser fiber blend and a hydrophilic treatment so water spreads evenly through the block instead of channeling down one side. That gives more uniform moisture and nutrient levels across a tray of seedlings, which matters when you run hundreds of cubes at once. They are a bulk commercial format: a case of 2,250 suits propagators and small farms more than a home gardener starting a few seeds.
In stock
Lowest price we've seen: $476.43 on Nov 7 at HTG Supply. Tracked across 1 store since Nov 7.
Buyers rate these blocks highly, with the even wetting and consistent block size standing out. Few complaints, mostly about the bulk quantity and the prep work rockwool needs.
Grodan Gro-Blocks are 1.5-inch square rockwool cubes. This improved version has a new density and new hydrophilic technology. It is sold as a case of 2,250 cubes.
The blocks distribute water and nutrients uniformly throughout, which supports better water distribution and root development. They saturate fully with no dry spots, and EC control improves while using less water. They re-wet more easily, which makes it simpler to raise water concentration in the substrate. Water holding capacity is excellent.