Grodan Improved Gro-Block GR4, 3 x 3 x 2.5 in with Hole, Unwrapped, Case of 384

Grodan Improved Gro Block GR4 Small, 3 in with Hole

Rooted cuttings and seedlings move into this block once they outgrow a plug or starter cube. Each GR4 Small measures 7.5 x 7.5 x 6.5 centimeters, which is 3 x 3 x 2.5 inches. A pre-formed hole in the top accepts the plug without cutting. The blocks in this case come unwrapped, so the sides are bare stone wool. That suits growers who run blocks tight on a bench and steer by weight. Grodan's Advanced Wetting Agent spreads water and EC evenly over the full height of the block. Even moisture from top to bottom helps roots use the whole volume instead of one wet corner. In Grodan's trials, the rooting-in phase ran several days faster. The block keeps its firmness and shape through the propagation stage. Grooves on the underside give excess solution a path to drain. Stone wool is inert, so the grower controls every nutrient that reaches the roots. A case of 384 fills several propagation trays at once.

Saturating a Rockwool Block Before Transplant

Mix a light nutrient solution and adjust it to pH 5.5 to 6.5. Fill a tub deep enough to cover the blocks completely. Drop the blocks in and let them sink, which takes about 10 to 15 seconds for this size. Leave them under until the bubbling stops. Do not soak them longer than 20 minutes. Lift them out and set them on the bench with the grooves running toward the drain. For overhead saturation, space the blocks close together but not touching. Pass over them 6 to 8 times with a coarse spray at a steady pace. Splitting the water into 3 or 4 lighter sessions works better than one heavy soak. Weigh a few blocks from different spots to confirm saturation. A fully wet GR4 Small weighs about 11.5 ounces, or 325 grams. Set the rooted plug into the hole and water it in lightly.

Key Features

• 3 x 3 x 2.5 in Block: GR4 Small size at 7.5 x 7.5 x 6.5 cm.
• Pre-Formed Hole: Accepts a starter plug without cutting.
• Unwrapped: No shrink wrap on the sides, for tight bench spacing.
• Advanced Wetting Agent: Even water content and EC over the full block height.
• Case of 384: Enough blocks to fill several propagation trays.

Technical Specifications