Grodan Rockwool Stonewool 4 Inch Gro Blocks, Case of 144
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$143.86at HTG SupplyChecked Nov 7
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Grodan 4-inch Gro Blocks are unwrapped stonewool cubes for hydroponic growing, sold in a commercial case of 144. Each block has a pre-formed top hole sized for Grodan A-OK Starters and Macroplugs, so a seedling or plug drops in and roots through. They work as either an intermediate step before a larger slab or as the final container. The Improved formulation with an advanced wetting agent is the main draw over plain rockwool: more even water content and EC across the block, which means more uniform crops and faster rooting-in. Growers pick them for cleanliness and speed versus coco coir or expanded clay, but the case size and the need to soak and pH-adjust before use make them a poor fit for a single-plant hobbyist.
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Lowest price we've seen: $126.54 on Nov 7 at HTG Supply. Tracked across 1 store since Nov 7.
Growers who use Grodan blocks in propagation trays report fast, even rooting and consistent blocks from cube to cube. The main complaints are the commitment of a full case and the prep work before planting.
These Grodan 4-inch Gro Blocks are made of rockwool (also called stonewool), a soilless growing substrate. Grodan has made rockwool in Denmark since 1969. Rockwool is an alternative to coco coir and expanded clay in hydroponic growing.
Each block can be used as an intermediary or final container for planting. A pre-formed hole on top fits Grodan A-OK Starters and Macroplugs snugly. The blocks are treated with an advanced wetting agent for crop uniformity, with more even water content (WC) and electrical conductivity (EC) distribution. They are designed for faster rooting-in and rooting-through, which speeds up the vegetative phase and time to harvest.
The blocks come unwrapped, and the product may differ from the image.