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Products > Growing Media > Grodan Rockwool

Rockwool is made from molten rock spun into fibers like cotton candy. It's then pressed into different shapes and cut into cubes and slabs. The cubes and slabs feel like a sponge and will not breakdown. The small Multiblocks and Miniblocks can be used for starting cuttings or seeds. After the plants grow out of the small blocks, you can place them in the holes in the larger growing locks. From there you can place them on a slab for larger plants. Although the rockwool can be heat sterilized after use and re bagged, most hobby growers just throw them away after use. The Grodan Growcubes are small squares of rockwool about the size of a sugar cube. They are used for filling pots or mixing with Hydroton for added moisture. The Granulated rockwool is also for filling pots and is less expensive than the Growcubes but does not have the same aeration.


Growing Blocks are used for small plants in a flood / drain tray

Multiblocks are used for seedlings and cuttings

Miniblocks for seedlings and cuttings

Granulated for filling pots

Hugo Blocks for larger plants, best with a drip system

Slabs for large plants watered by drip irrigation.

Growcubes in a pot

Need a full case of Rockwool?

Learn More About Rockwool.

  What's Availability?  
Description Availability Price

Grodan Multiblocks AO 36/40 1.4"x1.4"x1.5", 98 Per Sheet

Multiblocks are designed for cuttings or seed propagation and fit in the holes cut in the larger Rockwool cubes. The blocks come in sheets cut to fit in a standard 10" x 20" propagation tray. The blocks are tapered or V shaped to create an air space below... More Details

Item Number: 111003

Grodan Multiblocks AO 36/40 1.4"x1.4"x1.5", 98 Per Sheet
Usually ships in 24 hours $9.64

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Grodan Miniblocks Delta 40/40 1.5"x1.5"x1.5", 15 Per Strip, Pack of 3 Strips

These cubes measure 1.5" x 1.5" x 1.5" and work very well for seedling and cutting propagation. Each cube is wrapped in plastic on four sides to help hold in moisture. Pack of 45. To root cuttings, use the 10 x 20 inch tray, insert and dome. The cubes fit... More Details

Item Number: 111040

Grodan Miniblocks Delta 40/40 1.5"x1.5"x1.5", 15 Per Strip, Pack of 3 Strips
Usually ships in 24 hours $6.61

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Grodan Delta 4 Gro-Blocks 3x3x2.5 With Hole, Strip of 8

3 x 3 x 3 inch Growing Blocks with holes for smaller cubes. Used as a second stage from smaller cubes. The 1-1/2 inch round hole will accept the small cubes that come in a sheet or the wrapped cubes that come in a strip. Growing blocks are great for ebb a... More Details

Item Number: 111043

Grodan Delta 4 Gro-Blocks 3x3x2.5 With Hole, Strip of 8
Usually ships in 24 hours $4.16

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Grodan Delta 5.6 Gro-Blocks 3x3x4 With Hole, Strip of 8

3 x 3 x 4 inch Growing Blocks with holes for smaller cubes. Used as a second stage from smaller cubes. The 1-1/2 inch round hole will accept the small cubes that come in a sheet or the wrapped cubes that come in a strip. Growing blocks are great for ebb a... More Details

Item Number: 111044

Grodan Delta 5.6 Gro-Blocks 3x3x4 With Hole, Strip of 8
Usually ships in 24 hours $6.24

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Grodan Delta 8 Gro-Blocks 4x4x3 No Hole, Strip of 6

4 x 4 x 3 inch Growing Blocks without holes. Used as a second stage from smaller cubes, just place the small cube on top. Growing blocks are great for ebb and flow hydroponic systems or for use as mid stage for plants eventually going on to Rockwool slabs... More Details

Item Number: 111046

Grodan Delta 8 Gro-Blocks 4x4x3 No Hole, Strip of 6
Usually ships in 24 hours $5.99

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Grodan Delta 8 Gro-Blocks 4x4x3 With Hole, Strip of 6

4 x 4 x 3 inch Growing Blocks with holes for smaller cubes. Used as a second stage from smaller cubes. The 1-1/2 inch round hole will accept the small cubes that come in a sheet or the wrapped cubes that come in a strip. Growing blocks are great for ebb a... More Details

Item Number: 111047

Grodan Delta 8 Gro-Blocks 4x4x3 With Hole, Strip of 6
Usually ships in 24 hours $5.99

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Grodan Delta 10 Gro-Blocks 4x4x4 With Hole, Strip of 6

This is the most popular size rockwool cube. 4 x 4 x 4 inch Growing Blocks with holes for smaller cubes. Used as a second stage from smaller cubes. The 1-1/2 inch hole will accept the small cubes that come in a sheet or the wrapped cubes that come in a st... More Details

Item Number: 111048

Grodan Delta 10 Gro-Blocks 4x4x4 With Hole, Strip of 6
Usually ships in 24 hours $7.01

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Grodan Hugo Gro-Block 6x6x5.5, One Cube

The largest rockwool block. 6 x 6 x 6 inch Growing blocks with 1-1/2 inch hole for smaller cubes. Used for growing real big plants. These cubes work best with a drip system. In a flood system the top half can dry out quickly and lead to salt buildup so ri... More Details

Item Number: 111016

Grodan Hugo Gro-Block 6x6x5.5, One Cube
Usually ships in 24 hours $2.71

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Grodan Expert 15/75 6"x3"x36" Slab, One Slab

6 x 3 x 36 inch rockwool slab. Growing Slabs are a great choice for vegetable crops or almost any plant that needs extra support at the base. Slabs come wrapped in U.V. resistant plastic that makes a good container for the roots to thrive. A 3 foot slab c... More Details

Item Number: 111024

Grodan Expert 15/75 6"x3"x36" Slab, One Slab
Usually ships in 24 hours $5.80

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Grodan Expert 20/75 8"x3"x36" Slab, One Slab

8 x 3 x 36 inch rockwool slab, most popular size. Growing Slabs are a great choice for vegetable crops or almost any plant that needs extra support at the base. Slabs come wrapped in U.V. resistant plastic that makes a good container for the roots to thri... More Details

Item Number: 111026

Grodan Expert 20/75 8"x3"x36" Slab, One Slab
Usually ships in 24 hours $7.53

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Grodan Classic 30/75 12"x3x36" Slab, One Slab

12 x 3 x 36 inch rockwool slab. Growing Slabs are a great choice for vegetable crops or almost any plant that needs extra support at the base. Slabs come wrapped in U.V. resistant plastic that makes a good container for the roots to thrive. A 3 foot slab ... More Details

Item Number: 111028

Grodan Classic 30/75 12"x3x36" Slab, One Slab
Usually ships in 24 hours $11.34

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Macro Plugs, Bag of 32

The Clone Plugs fit in the round holds in the 3 and 4 inch growing blocks. They are slit so you can open them up and place your cutting inside. This will keep the cloning gel in place and help with rooting. Learn About Rockwool ... More Details

Item Number: 111001

Macro Plugs, Bag of 32
Usually ships in 24 hours $5.04

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Growcubes 2 Cubic Foot bag

Growcubes are an ideal hydroponic substrate for growing many crops. Ideally suited for top irrigation (watering can or drip system), the product also performs well under ebb & flow applications. Easy to use and environmentally friendly, growcubes provide ... More Details

Item Number: 111051

Growcubes 2 Cubic Foot bag
Usually ships in 3 to 5 days. $31.73

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Grodan Water absorbent (WA-20) 3.5 cubic feet (compressed) 45 lbs

AgroDynamics Granulate Granulated rockwool can be used alone or as an amendment to organic based mixes. For example, the addition of water absorbant granulate to peat mixes at 25-50% volume, increases water holding capacity and aeration, improving plant g... More Details

Item Number: 111036

Grodan Water absorbent (WA-20) 3.5 cubic feet (compressed) 45 lbs
Usually ships in 3 to 5 days. $66.97

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Grodan Water repellent (WR-20) 3.5 cubic feet (compressed) 45 lbs

AgroDynamics Granulate Granulated rockwool can be used alone or as an amendment to organic based mixes. For example, the addition of water absorbant granulate to peat mixes at 25-50% volume, increases water holding capacity and aeration, improving plant g... More Details

Item Number: 111037

Grodan Water repellent (WR-20) 3.5 cubic feet (compressed) 45 lbs
Usually ships in 3 to 5 days. $73.02

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