Grodan Improved Gro-Slab, 36 x 6 x 4 with three 4 x 4 pre-cut holes

Wide-Steering-Range Pre-Cut Stonewool Slab, 36x6x4in, 3x4x4in Holes

A slab that arrives without a planting hole still needs one cut before transplant, which adds a step and a chance for an inconsistent cut across a large planting. Grodan Improved Pre-Cut Gro-Slabs ship with the Advanced Wetting Agent technology and pre-cut holes already sized and positioned, so growers can transplant directly into the slab without cutting their own openings.

This 36in x 6in x 4in slab has three 4in x 4in pre-cut holes for direct transplant.

Key Features & Benefits

• Advanced Wetting Agent — retains moisture more evenly and reduces the risk of individual slabs drying out between irrigation cycles.
• Pre-cut holes — sized and positioned for immediate transplant without on-site cutting.
• Vertical fibrous structure — lets roots penetrate the slab easily as they grow out of the starter block.
• Wide irrigation range — growers can vary water volume within roughly a 55% to 78% day-level range while maintaining steerability.

Who Should Use Pre-Cut Gro-Slabs

Growers who want to transplant directly into the slab without cutting their own holes, especially across a large planting where consistent hole placement matters, are the best fit for the pre-cut format.

About Grodan

Grodan has built engineered stone wool growing media since 1969 as part of the ROCKWOOL Group. Its pre-cut Gro-Slab format applies the same Advanced Wetting Agent technology used across the Improved product line, with holes already cut for direct transplant.

Frequently Asked Questions

What does the Advanced Wetting Agent do on this slab?

It's designed to retain moisture more evenly throughout the slab, reducing the risk of individual slabs drying out faster than others in the same run. This supports the wider irrigation range the slab is built for.

How much can I vary irrigation volume with this slab?

The slab is built to handle water volume varying within roughly a 55% to 78% day-level range while still supporting precise crop steering. Growers should still monitor individual slab behavior rather than assuming every slab in a run performs identically.

What hole configuration does this slab have?

Configurations vary by size: one version has three 4in x 4in pre-cut holes in a 36in x 6in x 4in slab, while another has three 6in x 6in pre-cut holes in a 36in x 8in x 3in slab. Both ship ready for direct transplant without on-site cutting.

Can this slab be resaturated quickly if it's underwatered?

Yes, if a slab is allowed to dry down more than intended, it can be resaturated quickly at any point in the cycle. That said, consistent irrigation scheduling remains the more reliable way to manage water content across a run.

Why does vertical fiber orientation matter for root penetration?

A vertical fibrous structure gives roots a more direct downward path as they grow out of the starter block into the slab, supporting faster and more uniform root penetration. This is a structural property of the slab rather than an added treatment.