Grodan Improved Gro-Slab, 36 x 6 x 3, case of 12

Wide-Steering-Range Stonewool Slab for Crop Uniformity, 36x6x3in

Achieving consistent water content and electrical conductivity across every slab in a run is one of the harder parts of steering a stonewool crop, since small differences in wetting behavior compound across a growing area. Grodan Improved Gro-Slab uses an Advanced Wetting Agent and a vertical fiber orientation to keep water content and EC distribution more uniform slab to slab, giving growers a wider, more predictable steering range.

This 36in x 6in x 3in slab ships in a case of 12 without pre-cut holes, suited to growers who cut their own planting openings to match a specific block or plug size.

Key Features & Benefits

• Advanced Wetting Agent — improves water distribution uniformity throughout the slab and from slab to slab.
• Vertical fiber orientation — supports fast, even root penetration and uniform stem development.
• High resaturation capacity — the slab rewets quickly if it's allowed to dry down between irrigation cycles.
• No pre-cut holes — growers cut planting openings sized to their own blocks or plugs rather than a fixed hole size.

Who Should Use This Slab

Growers who want to cut their own planting openings, to match a specific starter block or plug size rather than a fixed pre-cut hole, are the best fit for this uncut slab format. It suits both commercial stonewool operations and growers transitioning from another substrate.

About Grodan

Grodan pioneered engineered stone wool growing media in 1969 and operates today as part of ROCKWOOL Group, supplying stonewool substrate for professional greenhouse and controlled-environment growers.

Frequently Asked Questions

What does Grodan's Advanced Wetting Agent do?

It's designed to improve how evenly water and nutrient solution distribute throughout the slab and from one slab to the next in the same run, which is what gives growers a wider steering range. Without it, wetting behavior can vary enough between slabs to create uneven crop development across a growing area.

How do I cut a planting hole in this slab?

Since this slab ships without pre-cut holes, cut an opening sized to your specific starter block or plug using a clean blade, positioning it based on your plant spacing plan. Cutting your own hole lets you match the opening exactly to the block size you're using instead of working around a fixed cut.

What does 'vertical fiber orientation' mean for root development?

The stonewool fibers run vertically through the slab, giving roots a more direct path downward as they grow out of the starter block. This supports faster, more uniform root penetration than a fiber structure with no consistent orientation.

Can this slab be resaturated quickly if it dries out?

Yes, the slab's high resaturation capacity means it rewets quickly if it's allowed to dry down between irrigation cycles. That said, consistent irrigation scheduling is still the more reliable way to manage water content across a run.

Is this the same slab as Grodan's pre-cut Gro-Slab options?

It uses the same Advanced Wetting Agent and fiber technology as Grodan's pre-cut slabs, just without holes already cut, so growers can size their own openings. Growers who want a ready-to-transplant slab without cutting should look at Grodan's pre-cut Gro-Slab options instead.