Description
Same block, one extra hole. This is the standard Grodan 6" Hugo rockwool block, 150 x 150 x 140mm with the usual 36mm cavity for a propagation cube, plus a second purpose-made hole for a dripper.
Being straight with you: the dripper hole is larger than we expected and there is only one of them, so it looked like a manufacturing change nobody told us about. Grodan say marketing material explaining the benefit is coming. We are still waiting. In the meantime it grows exactly like the original.
Want the plain one instead?
The original Grodan 6" Hugo Block is the same size and the same wool, with the single 36mm hole and nothing else. If you feed from the top with a 6" FLORACAP or a bubbler rather than a dripper stake, that is the one to take.
Specification
| Block dimensions | Approx. 150 x 150 x 140mm |
| Main hole | 36mm, takes a standard propagation cube |
| Second hole | Dripper hole, one per block |
| Weight | Approx. 0.26kg dry per block, 12.59kg a box of 48 |
| Recommended run-off | 10 to 30% per feed |
| Pre-soak pH | 5.5 to 5.8 before transplanting |
Before you use them
Rockwool leaves the factory with a naturally high pH, so it has to be conditioned before anything goes in it. Soak for 24 hours in a weak nutrient solution under 1.0 EC, adjusted to pH 5.5. A small amount of root stimulant in the soak water lifts the EC and gets roots moving faster. Let it drain until damp rather than dripping. Skip this and you will see the first week of growth stall.
Which rockwool size do I need?
Rockwool works as a ladder. You start small and pot on into the next size up, each time without disturbing the roots. Here is the full range we stock and where each one sits.
| Product | Size | Where it fits | Takes |
|---|---|---|---|
| Grodan Propagation Cubes | 25mm or 36mm | Seed and cutting | Bare cutting or seed |
| Cultiwool Loose Mini Cubes | 10mm, 90L or 200L | Loose fill, any pot | Fills pots and trays |
| Cultiwool Mapito | 80L bag | Loose fill, any pot | Fills pots and trays |
| Grodan Block 3" | 7.5cm | First pot-on | 2.5cm or 3.6cm hole |
| Grodan Improved GR4 3" | 3 x 3 x 2.5" | First pot-on | Pre-formed hole |
| Grodan Block 4" | 10cm | Veg | 2.5cm or 3.6cm hole |
| Grodan Improved GR10 4" | 4 x 4 x 3.1" | Veg | Pre-formed hole |
| Grodan 6" Hugo Block | 150 x 150 x 140mm | Veg to harvest | 36mm hole |
| Grodan 6" Hugo, dripper hole (this product) | 150 x 150 x 140mm | Veg to harvest | 36mm hole plus dripper hole |
| Grodan Improved Hugo 6" | 6 x 6 x 5.8" | Veg to harvest | Pre-formed hole |
| Cultiwool 8" Big Daddy Block | 20 x 20 x 19.5cm | Full cycle, large plants | Takes an 8" cap |
| Cultiwool 25cm X-Fibre Mini Slab | 25.2 x 19.5 x 7.5cm | Under a block, full cycle | One 6" or 8" block sits on top |
| Grodan Vital Slab 1m | 100 x 15 x 7.5cm | Multi-plant, full cycle | Three to four blocks |
| Grodan Vital Slab 1.3m | 130 x 15 x 7.5cm | Multi-plant, full cycle | Four to five blocks |
Sizes are nominal. Blocks are sold as singles or in strips depending on the line.
Goes well with
- Grodan 6" Hugo Block – The original, same size, single hole.
- Octa-Mitter 360 Dripper on Stake – Adjustable 0 to 60 L/h, if you are going to use that dripper hole.
- FloraFlex 6" FLORACAP 3.0 – Sized for a 6" block. Spreads the feed across the whole top and keeps light off the wool.
- Grodan Propagation Cubes – The 36mm cube drops straight into the main hole.
- Cultiwool 25cm X-Fibre Mini Slab – Sits under a 6" block for extra root mass and a bigger buffer.
Frequently asked questions
Is this a different block to the original Hugo?
No. Same wool, same 150 x 150 x 140mm, same 36mm cube hole. The only difference is the extra dripper hole. Grow them the same way.
Do I have to use the dripper hole?
No. Feed from the top as normal and it makes no difference. If you do use it, put a dripper stake in it rather than leaving it open, so you are not channelling feed straight past the root zone.
Which cap fits a 6 inch block?
The FloraFlex 6" FLORACAP 3.0. The 8" cap is for the Cultiwool Big Daddy, so do not order that one by mistake.
Do I have to soak them first?
Rockwool leaves the factory with a naturally high pH, so it has to be conditioned before anything goes in it. Soak for 24 hours in a weak nutrient solution under 1.0 EC, adjusted to pH 5.5. A small amount of root stimulant in the soak water lifts the EC and gets roots moving faster. Let it drain until damp rather than dripping.
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Rockwool · Growing Media · Dripper Systems · Run to Waste Systems · Grow Room Irrigation

