Grodan Gro-Block Improved Large 4 GR10 w/ hole (4x4x4) (PRO-unwrapped)

What Arrives in a Case of Grodan 4x4x4 Blocks

This is a full case of Grodan Improved four inch blocks rather than a single block. One hundred and forty-four blocks come in twenty-four strips of six, and a pallet holds twelve of those cases. Each block is four inches cubed with a pre-cut hole in the top, sized to take a rooted starter plug. The strips arrive unwrapped in the carton, which is the PRO packaging rather than the retail format. That matters in two directions. Unwrapped stone wool has no film holding water at the sides, so it dries from every face rather than only the top. Exposed faces in the light will grow algae in a wet room. Against that, the root mass stays visible and the cost per block is lower. There is also no plastic to strip and discard on a hundred and forty-four units. Growers running a tight irrigation schedule generally prefer the exposure. The material is stone wool and the grade is GR10, from the Improved range that Grodan developed with research partners.

Wetting Agent, Dry Back and Conditioning Before Use

The Improved range is built around a wetting agent worked into the wool itself. Two things follow from that. Water and nutrient spread laterally through the block instead of channelling down one path. That is what keeps a corner from staying dry while the centre floods. Re-wetting is considerably easier too. A block allowed down to a low water content takes a feed back up evenly rather than shedding it. That second property is the whole basis of steering in stone wool. A controlled drop in water content between irrigations is the lever a grower actually pulls. A substrate that will not re-wet cleanly takes that lever away. Condition the blocks before anything goes into them. Stone wool leaves the factory alkaline, which is why it gets a soak in pH-adjusted water. Skipping it locks up iron and other elements in the first week. The case ships at around 26 lb in a carton of roughly 16.5 by 24.5 by 24.3 inches.

Key Features

• Case contents: A hundred and forty-four blocks, in twenty-four strips of six
• Block size: Four inches cubed, with a pre-cut hole for a starter plug
• Packaging: PRO unwrapped strips in a carton, with no film on each block
• Unwrapped trade-off: Faster drying and visible roots, but algae on lit faces
• Pallet: Twelve cases to a pallet at this block size
• Grade: GR10, from the Grodan Improved range
• Wetting agent: Worked into the wool, spreading water and feed laterally
• Re-wetting: A dried block takes a feed back up evenly rather than shedding it
• Steering: Controlled water content between irrigations is the working lever
• Before use: Condition in pH-adjusted water, as Grodan direct

Technical Specifications