Grodan Gro-Block Improved GR22.5 Jumbo 6" x 6" x 4" (64/Case)

The Grodan Gro-Block Improved GR22.5 Jumbo 6" x 6" x 4" (64/Case) is a professional stone wool growing block engineered for precise root-zone management in hydroponic, indoor, greenhouse, and controlled-environment growing systems. Grodan Improved technology combines an optimized stone wool fibre structure with an Advanced Wetting Agent to promote more uniform water distribution, stable EC management, and efficient root development throughout the entire substrate volume.

Each GR22.5 Jumbo block measures 6 × 6 × 4 in (15 × 15 × 10 cm) and provides approximately 2.25 L of stone wool substrate volume. Each case contains 64 blocks, making this large-format block ideal for commercial growers who want precise irrigation control and a substantial root zone without the added height of a 6-inch-tall block.

What Is the Grodan GR22.5 Jumbo Used For?

The Grodan Gro-Block Improved GR22.5 Jumbo provides a larger stone wool root zone for established young plants after the propagation stage.

A rooted starter plug or young plant can be placed into the block, allowing the roots to expand throughout the stone wool while the grower precisely controls irrigation, nutrient concentration, EC, pH, moisture content, and dry-back.

Its 6 × 6 in footprint combined with a 4 in height provides substantial horizontal root-zone volume while maintaining a relatively low profile.

Key Benefits

• Professional Grodan improved stone wool growing block.
• 6 × 6 × 4 in nominal dimensions.
• Metric dimensions of approximately 15 × 15 × 10 cm.
• Approximately 2.25 L of substrate volume per block.
• 64 blocks per case.
• Grodan Advanced Wetting Agent for improved initial saturation.
• Optimized fibre structure for crop uniformity.
• More even water content throughout the block.
• More uniform EC distribution within the root zone.
• Supports rapid and uniform root development.
• Provides strong vegetative and generative crop-steering potential.
• Designed for precise irrigation and fertigation strategies.
• Suitable for indoor cultivation, greenhouses, hydroponics, and controlled-environment agriculture.

What Is Different About Grodan Improved?

The Grodan Improved range was developed to provide growers with greater control over water content, EC, and root-zone conditions.

An optimized fibre structure combined with Grodan’s Advanced Wetting Agent improves initial saturation and helps water distribute more evenly throughout the height and width of the block.

More uniform water content and EC allow irrigation strategies to influence plant development more predictably while helping roots make efficient use of the available substrate volume.

How Does the Advanced Wetting Agent Help?

Grodan’s Advanced Wetting Agent is designed to improve the way irrigation solution enters and spreads throughout the stone wool.

Improved initial saturation and water distribution help reduce inconsistencies in moisture levels within the block.

This gives growers more control over root-zone moisture and helps maintain more stable conditions for nutrient and water uptake.

Uniform Water Content and EC Distribution

The Grodan Improved fibre structure is designed to provide more consistent water content (WC) and electrical conductivity (EC) throughout the block.

Uniformity is particularly valuable in precision cultivation because it allows irrigation volume and frequency to be adjusted more predictably.

This helps growers use irrigation events and dry-back periods as part of their crop-management strategy.

Enhanced Root Development

Grodan Improved blocks are engineered so roots can establish and expand throughout the available substrate volume.

A more uniform distribution of water and air encourages roots to colonize the block instead of concentrating primarily in isolated wet areas.

Effective use of the full substrate volume can help improve access to water, nutrients, and oxygen throughout the root zone.

Greater Crop-Steering Control

The GR22.5 Jumbo is designed for growers using precise irrigation strategies to influence plant development.

Because water content and EC can be managed consistently throughout the block, growers can adjust irrigation timing, frequency, and volume according to the desired vegetative or generative response.

This makes the GR22.5 particularly suitable for professional cultivation systems where root-zone steering is an important component of crop management.

Why Choose a 6" x 6" x 4" Growing Block?

The 6 × 6 × 4 in format provides a large horizontal root zone while maintaining a lower profile than a 6 × 6 × 6 in block.

Its approximately 2.25 L substrate volume offers considerably more rooting capacity than smaller 4-inch blocks while still allowing responsive irrigation and dry-back management.

This combination makes the Jumbo block suitable for established plants that require more root space without necessarily requiring the additional substrate volume of the taller Grodan Hugo block.

Ideal Applications

The Grodan Gro-Block Improved GR22.5 Jumbo 6" x 6" x 4" (64/Case) is suitable for:

• Hydroponic cultivation
• Drip irrigation systems
• Precision fertigation
• Indoor horticulture
• Commercial greenhouse production
• Controlled-environment agriculture
• Vegetative plant development
• Flowering and fruiting crops
• Root-zone steering strategies
• Transplanting rooted propagation plugs
• High-performance horticultural production
• Professional commercial growing operations

Product Specifications

How Do You Use the Grodan GR22.5 Jumbo Block?

Before transplanting, fully hydrate and condition the Grodan block according to your crop and nutrient program.

Once the block has reached the desired moisture, EC, and pH conditions, place the rooted propagation plug or young plant into the opening at the top of the block.

During cultivation, adjust irrigation frequency and volume according to plant size, crop stage, environmental conditions, water content, EC, and desired dry-back.

Because the GR22.5 has a relatively large substrate volume, irrigation strategy can be adjusted progressively as the root system expands throughout the block.

Can Rooted Starter Plugs Be Transplanted Into the GR22.5 Jumbo?

Yes. The Grodan GR22.5 Jumbo is designed to receive rooted starter plugs or young plants.

Once the starter plug has developed a healthy root system, it can be placed into the larger Grodan block so the roots can continue expanding throughout the stone wool.

Can the GR22.5 Jumbo Be Used With Drip Irrigation?

Yes. The GR22.5 Jumbo is particularly well suited to drip irrigation and precision fertigation systems.

Its improved water distribution allows growers to manage irrigation events, nutrient delivery, EC, and dry-back with a high degree of control.

What Is the Difference Between the Grodan Jumbo and Hugo Blocks?

The Grodan GR22.5 Jumbo measures 6 × 6 × 4 in (15 × 15 × 10 cm), while the Grodan GR32 Hugo measures approximately 6 × 6 × 6 in (15 × 15 × 14.2 cm).

The Jumbo provides a lower-profile root zone with approximately 2.25 L of substrate, making it more responsive to irrigation adjustments.

The taller Hugo provides additional substrate volume and therefore a larger moisture and root-zone buffer.

What Is the Difference Between Grodan Improved and Standard Stone Wool Blocks?

Grodan Improved blocks incorporate an optimized fibre structure and Advanced Wetting Agent technology specifically designed to improve initial saturation, water distribution, EC uniformity, and root development.

These characteristics provide growers with greater control over irrigation and root-zone conditions throughout the production cycle.

Who Is the Grodan GR22.5 Jumbo Best For?

The Grodan Gro-Block Improved GR22.5 Jumbo is particularly suitable for growers who need a large professional stone wool block with precise control over moisture, EC, nutrient delivery, and root-zone development.

The 64-block case is well suited to commercial greenhouses, indoor cultivation facilities, hydroponic producers, controlled-environment agriculture operations, and professional horticultural growers.

Frequently Asked Questions

How many Grodan GR22.5 Jumbo blocks are included in one case?
Each case contains 64 blocks.

What are the dimensions of the GR22.5 Jumbo?
Each block measures 6 × 6 × 4 in, approximately 15 × 15 × 10 cm.

What is the approximate substrate volume?
Each block provides approximately 2.25 L of stone wool substrate volume.

What does Grodan Improved mean?
Grodan Improved combines an optimized stone wool fibre structure with an Advanced Wetting Agent to support more uniform water content, EC distribution, and root development.

Can rooted starter plugs be transplanted into the Jumbo block?
Yes. Rooted propagation plugs and young plants can be transferred into the GR22.5 Jumbo for continued root development.

Can the GR22.5 be used with drip irrigation?
Yes. It is particularly well suited to drip irrigation and precision fertigation systems.

Is the GR22.5 Jumbo smaller than the Grodan Hugo?
Yes. Both have a 6 × 6 in footprint, but the Jumbo is approximately 4 in high, while the Hugo is approximately 6 in high.