Grodan Rockwool Gro-Slab with Holes 8" x 36" x 3", Case of 12
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Our take on the Grodan Rockwool Gro-Slab with Holes 8" x 36" x 3", Case of 12
Grodan Gro-Slab is a 3-inch-thick rockwool slab with pre-cut planting holes, sized 8 x 36 inches, sold in a case of 12. The vertical fiber orientation spreads water evenly across the slab and re-saturates quickly, which suits drip-fed hydroponic setups with several plants per slab. It is an inert, single-season growing medium, so it is replaced between crops rather than reused indefinitely. No current price was provided for this listing, so compare case prices across stores before buying.
- Pre-cut holes save planting time
- Vertical fiber orientation spreads water and nutrients evenly
- High re-saturation capacity after dry-back
- 3-inch thickness gives roots room on a 36-inch slab
- Case of 12 covers a full run of slabs
Grodan Rockwool Gro-Slab with Holes 8" x 36" x 3", Case of 12 prices at every store
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Grodan Rockwool Gro-Slab with Holes 8" x 36" x 3", Case of 12 price history
Lowest price we've seen: $102.05 on Nov 7 at HTG Supply. Tracked across 1 store since Nov 7.
What reviewers say
Growers who use Grodan slabs report even moisture across the slab and quick rooting after transplant. Complaints center on slabs drying unevenly at the ends and on the bulk of buying by the case.
- Water distributionPraisedGrowers say water and nutrients spread evenly through the slab.
- Rooting speedPraisedPlants root quickly after being set into the pre-cut holes.
- Moisture at endsCriticisedSome report the slab ends dry out faster than the center.
Questions and answers
- How many plants fit in one slab?
- The 36-inch slab with pre-cut holes is typically used for 4 to 6 plants, depending on crop and spacing. Larger plants like tomatoes need more room per slab.
- Can I reuse Grodan slabs for a second crop?
- Rockwool slabs are usually treated as single-crop media in hydroponics. Reusing them risks root disease and salt buildup, so most growers replace them each run.
- Do I need a drip system for these slabs?
- Yes. Slabs are designed for drip or top-feed irrigation with drainage. Hand-watering a slab evenly is difficult.
- Is this rockwool OMRI certified?
- The listing states no OMRI certification. Check the packaging or Grodan's site if organic certification matters for your operation.
- What size is each slab?
- Each slab measures 8 x 36 x 3 inches, and the case contains 12 slabs.