Grodan Delta 6.5 with Hole, 4" x 4" x 2.5" - Case of 36
Grodan Delta 6.5 with Hole, 4" x 4" x 2.5" - Case of 36 - Hydroponics

Grodan Delta 6.5 with Hole, 4" x 4" x 2.5" - Case of 36

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Grodan Delta 6.5 with Hole, 4" x 4" x 2.5" - Case of 36

Grodan Delta 6.5 with Hole, 4" x 4" x 2.5" - Case of 36

$238.81 $139.92

Grodan Delta 6.5 with Hole, 4" x 4" x 2.5" - Case of 36

$238.81 $139.92

The Foundation for uniform and perfectly controllable propagation of plants.


Grodan Delta is the basis for an easy to steer propagation process, that results in uniform, good quality plants. Each block guarantees uniform water and nutrient distribution. Grodan Delta scores high in saturation and firmness, which means it always performs well in highly mechanized propagation processes.


Grodan Delta is a reliable propagation block for vegetable crops, and is used worldwide. The excellentwater distribution, degree of saturation and firmness safeguard the results under diverse growing conditions.

Delta Technology

Delta Technology ensures uniform distribution of water and nutrients throughout the block. Newly transplanted plants benefit thanks to the good availability of water and nutrients, which encourages the roots to penetrate deeply into the substrate slab.

What is Rockwool?

Grodan Stonewool (rockwool) is made from molten rock spun into cotton candy-like fibers and then compressed into cubes, blocks, or slabs. Where other rockwool brand manufacturers cut all sizes from one batch of wool, Grodan is unique by making different types of fibers. The purpose is to support the requirement of the plant in the different plant stages. Grodan has a tremendous capacity for absorbing nutrient solution while retaining plenty of oxygen for rapid plant growth. Grodan comes in graduated sizes. Seedlings started in cubes are easily transferred to blocks and then onto slabs, if desired. Seedlings or cuttings started in the Grodan cubes can also be transplanted into more traditional planters and growing mediums.

Grodan Delta Gro-Blocks come in a variety of sizes to cater to the needs of all growers

  • Delta 3" & 4" Blocks
    • Delta 4 w/ Hole - 3" x 3" x 2.5"
    • Delta 4 w/out Hole - 3" x 3" x 2.5"
    • Delta 5.6 w/ Hole - 3" x 3" x 4"
    • Delta 6.5 w/ Hole - 4" x 4" x 2.5"
    • Delta 10 w/ Hole - 4" x 4" x 2.5"
  • Delta Hugo Block - 6" x 6" x 6"
  • Delta Big Mama Block - 8" x 8" x 8"
Grodan Delta Product Line

3" & 4"

Whether starting your seeds and cuttings in A-OK Starters or Mini-Blocks it is a good idea to transplant into a 3" or 4" block. You know it's time to transplant to the Gro-Block when roots coming out of the starter are about 1" long. Just place your Mini-Block on top of the 3" or 4" block without the hole, or your Macroplug/A-OK into the 3" or 4" block with the hole and watch your plant flourish.


Hugo is large enough to grow out most vegetables and some fruits for the entire life span of the plant. Hugo's holes are the perfect size for any 1.5" A-OK starter plug or Macroplug. When your starter has outgrown its home, showing three leaves, or roots reaching one 1" below the cube, Hugo is happy to receive the transplant. Hugo is sold individually with instructions on the wrapping. Hand water or use with drippers or in Ebb & Flow (Flood) systems.

Big Mama

Big Mama is made for growing the largest plants and even small trees. If you want to grow a mother plant or just want to make a statement she will make you proud. Big Mama does not have pre-drilled holes because we recommend she be used in conjunction with a well rooted plant from a minimum 3" Gro-Block. Big Mama is sold with instructions on the wrapping. Big Mama DOES REQUIRE top feeding, so either hand water or use drippers.

Usage Instructions


  • Saturate the Grodan Gro-Blocks with pH 5.5-6.5 water when starting cuttings
  • When transplanting, use the same strength nutrient solution to soak the new media as you were feeding the plant.
  • If submerging the blocks to saturate, keep them submerged in the solution until bubbling stops


  • If using a drip irrigation system, use one drip stake per Grodan Gro-Block. Irrigate as needed to keep the block moist but not saturated.
  • If using an ebb and flow system, irrigate when the Grodan Gro-Block is approximately half its fully saturated weight.
  • If hand watering, keep the block moist but not full saturated.
  • Do not over saturate the block after the initial soak as this can slow plant growth


  • Place a rooted cutting, grown in Grodan starter, into the hole of the Grodan Gro-Block
  • Do not water for several days until the plant has rooted into the Grodan Gro-Block but do not allow the block to go completely dry
  • If needed, lightly mist once per day to keep the top of the block moist
  • Do not allow the block to sit in standing water

Transplanting for Larger Plants

  • For smaller short term crops, Grodan Gro-Blocks are all you need. To grow larger plants, you can transplant Gro-Blocks on to Grodan Slabs Grodan loose media, or soil
  • Prior to transplanting, make sure that the plant is well established with multiple roots appearing on the bottom of the Grodan Gro-Block
  • When transplanting to a container or outdoor garden, make sure the new media is very wet at the time of initial transplant

Grodan Delta Gro-Blocks Questions & Answers

Q: What is stone wool?
A: Stone wool is a mineral wool made of volcanic rock. Stone wool consists of 5% solid material in the form of stone fibres. The remaining 95% is made up of pores.

Q: How is stone wool made?
A: The basic materials for our stone wool are basalt and limestone. These are melted to form lava in an oven with a temperature of 1,500°C. The lava is then poured over a number of fast-rotating discs. Thanks to the centrifugal force, the drops fly off the discs and lengthen to form fibres. The process can be compared with candy floss being made at a fair. The fibres are then compressed to form a sturdy mass, from which the slabs and blocks are then cut.

Q: Why is stone wool suited for growing vegetables?
A: Our stone wool growing media are designed for Precision Growing in a greenhouse. Precision Growing focuses on ‘root zone management', or in other words, steering of the root environment. Everything that happens in the stone wool substrate has an impact on the functioning of the root environment and therefore the development of the plant. So, we continually investigate how our products, tools and user advice can respond perfectly to changing circumstances, so that the plant is given the very best care, without wasting resources.

Lead Time This product ships in 1 Business Day
Prop 65 No
EACH - Weight(lb) 25.42
EACH - Height(in) 24
EACH - Length(in) 24.5
EACH - Width(in) 16.5
Total Sold 0
Weight (lb) 24.13
Height (in) 24
UPC 856372001448
Width (in) 17
Brand Grodan
OMRI Certified No
Grow Media Rockwool
Select Rockwool Type Delta 6.5 w/ Hole - 4 x 4 x 2.5 - Case of 36

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