The classic Grodan Gro-Blocks have been a mainstay of professional hydroponic horticulture since their initial release in 2004. Grodan Gro-Blocks provide the foundation your plants need for healthy root development and vigorous growth.

Grodan Gro-Blocks – The Classic Stone Wool Solution

Grodan’s Gro-Blocks are used in grow rooms and greenhouses worldwide. Trusted by hydroponic growers for over a decade, Grodan Gro-Blocks allow professional cultivators to grow more top quality produce with fewer inputs. The homogeneity of Grodan Gro-Blocks provides growers with a solid, consistent base for optimizing crop production. Cultivators can easily achieve a great balance of oxygen to nutrients and drive rapid plant growth. Grodan  Gro-Blocks are clean, disease and pest free, lightweight, and easy-to-use. Professional growers love Grodan Gro-Blocks because they allow efficient use of water and nutrients throughout the growth cycle.

  • Effortless start-up of propagation. Grodan Gro-Blocks are perfect for propagating young plants under a wide range of propagating conditions. The Grodan Gro-Blocks are easy to saturate and water is distributed uniformly throughout the block, for reliable root development and plant growth
  • Excellent root growth throughout the block. The Grodan stone wool ensures uniform distribution of water and nutrients throughout the block, encouraging the roots to penetrate deeply into the block.
  • Greater firmness for better handling. During the propagation stage, blocks generally will be manually or mechanically handled several times. Due to the greater firmness of the Grodan Gro-Blocks, this handling is no problem and the Grodan Gro-Block will maintain its shape and structure. The stable firmness of the blocks becomes particularly important when the blocks are placed, spaced and picked up several times during propagation.
Grodan  Gro-Blocks: Available in Sizes to Suit Your Grow

Grodan 3” and 4” Gro-Blocks

Grodan  3” and 4” Gro-Blocks are ideal for supporting small plants throughout their lifecycle or for the early vegetative stage of larger plants before transplanting on to a Big Mama or Gro-Slab. Both size blocks are available in standard and shallow depths.

Grodan Hugo 6” Gro-Block

Grodan Hugo Gro-Blocks can support many species throughout their lifecycle. The Hugo comes with a pre-fabricated hole that’s perfectly sized to accommodate 1.5” Grodan A-OK Starter Plugs™. Be sure not to rush the propagation period and allow your seedlings or cuttings sufficient time to fully exploit the stone wool in the Grodan A-OK Starter Plug™ before transplanting.

Grodan Big Mama 8” Gro-Block

Our massive Grodan Big Mama 8” Gro-Blocks are the go-to for cultivators with the loftiest growing ambitions, able to support very large plants and even small trees throughout their lifecycle! Simply sit a plant, well-established in a Grodan 3” or 4” Gro-Block, directly on top of the Big Mama and the roots will quickly colonize their spacious new home. Big Mamas are not recommended for flood and drain — manual top feed or drip irrigation only. Adequate irrigation is critical to keep the Big Mama within the proper WC range.

Saturate Grodan Gro-Blocks in a nutrient solution of roughly 1.5 EC and 5.5 pH with a course spray or submerged in the solution for up to 2 minutes.
Do not over saturate the blocks or leave soaking for extended periods of time.

2. Measure wet weight
Measure the weight of the block at saturation. Compare this weight to the weight of the blocks throughout the growing cycle. When the WC of the block is 55% to 65% apply the first irrigation.

3. Transplant
Insert the well rooted Grodan Starter Plug into the hole of the saturated Gro-Block

4. Irrigation
We recommend using a pressure compensated drip irrigation system.Grodan White GR-4 and Grodan White GR-10 Gro-Blocks – insert 1 drip stake per blockGrodan White Jumbo and Grodan White Hugo Gro-Blocks – insert 2 drip stakes per block.Volume of irrigation should be 3% to 6% of growing media volume (for example, Grodan White Hugo is 100 mL to 200 mL)Irrigation Volumes (suggested flow rate is 0.5 gph (2 lph):

Shot Size % of Substrate Volume
Small 2%
Standard 3%
Large 4 – 6%

For more information on irrigation for Grodan Gro-Blocks, download Grodan Irrigation Strategy.

Gro-Blocks Dimensions (in) Dimensions (cm) Blocks/Package Blocks/Carton Blocks/Pallet
Grodan D 4 Small 3″ 3 x 3 x 2.6 7.6 x 7.6 x 6.6 8 384
Grodan D 5.6 Large 3″ 3 x 3 x 4 7.6 x 7.6 x 10.1 8 256
Grodan D 6.5 Small 4″ 4 x 4 x 2.6 10.1 x 10.1 x 6.4 6 216 2,592
Grodan D 8 Medium 4″ 4 x 4 x 3.1 10.1 x 10.1 x 8 6 192 2,304
Grodan D 10 Large 4″ 4 x 4 x 4 10.1 x 10.1 x 10.1 6 144 1,728
Grodan Hugo 6 x 6 x 6 15.2 x 15.2 x 14.2 64 512
Grodan Hugo (unboxed) 6 x 6 x 6 15.2 x 15.2 x 14.2 512
Grodan Big Mama 8 x 8 x 8 20.3 x 20.3 x 20.3 18 216