What a 36 Inch Grodan Rockwool Slab Changes About Flower
The slab is where a block crop goes to finish. Each one runs 36 x 6 x 3 in and a case holds 12. Dry weight of that case is about 15.4 lbs. Fibres lie horizontally rather than vertically, which spreads water sideways along the length instead of dropping it straight through. That is what lets three or four plants share one slab and still see comparable moisture at each station. These arrive without pre-cut holes, so spacing is yours to set with a knife. The honest limit is that unholed slabs take longer to set up than the pre-cut version, and on a big room that time adds up.
Setting Up a Stone Wool Grow Slab Under Existing Blocks
A stone wool grow slab needs saturating before anything sits on it. Drain slits get cut at the low end once the wool has taken up water. Blocks then go on top and roots find the slab within a few days. From there the slab holds the buffer while the block holds the plant. Vine crops like tomatoes and cucumbers use the same format, which is why the size has stayed unchanged for decades. Drippers, hand watering and flood benches all work, though a slight fall along the length makes drainage far more predictable. Because the wool is inert and pathogen free, there is no sterilising step and no residue from the previous crop to chase. Pargro is the value tier, so slab-to-slab uniformity is good rather than exceptional.
Key Features
- 36 inch length: One slab carries three or four stations, which cuts the number of drip lines needed.
- Horizontal fibre structure: Spreads water along the slab so moisture stays comparable at every plant.
- No pre-cut holes: Plant spacing is set by your own layout rather than by the factory.
- Case of 12: Roughly 15.4 lbs dry, enough slabs to lay out a full bench row.
- Inert basalt wool: No nutrient contribution and no pathogens, so nothing needs sterilising first.
- Blocks transplant on top: Rooted cubes sit straight onto the slab at flip with no root disturbance.
Technical Specifications
| Specification | Value |
|---|---|
| Brand | Grodan |
| Product Line | Pargro Quick Drain |
| Part Number | 328464 |
| Format | Slab, no pre-cut holes |
| Dimensions | 36 x 6 x 3 in |
| Case Count | 12 slabs |
| Case Weight | About 15.4 lbs dry |
| Material | Basalt stone wool, inert |
| Fibre Orientation | Horizontal |
| Drainage | Quick drain, cut your own drain slits |
| Typical Crops | Stone wool block crops, tomatoes, cucumbers and other vine crops |
| Suitable Systems | Drip irrigation, hand watering, flood benches |
| Nutrient Contribution | None, the substrate is inert |
