Speedgrow 75 x 75 x 65mm Propagation Cube – 38 x 35mm Large Hole Earthwool Starter Block

The Speedgrow 75 x 75 x 65mm Propagation Cube with 38 x 35mm hole is a professional-grade Earthwool starter block designed for seedlings, rooted cuttings and young plants moving from propagation into the next stage of growth.

Manufactured by Agra-Wool International, the Speedgrow range uses mineral fibres produced from basalt and bonded using ECOSE technology, an organic binder technology designed to create an open, root-friendly growing structure.

The generous 38mm diameter x 35mm deep planting hole is designed to accept larger propagation plugs, including compatible 38 x 35mm Speedgrow plugs, allowing young plants to be transplanted into a larger rooting volume with minimal disturbance.

With a compact 75 x 75 x 65mm format, this cube provides considerably more root space than a propagation plug while remaining small enough for efficient nursery, hydroponic and controlled-environment growing applications.

Key Features

• 75 x 75 x 65mm propagation/start block
• Large 38mm diameter x 35mm deep hole
• Manufactured by Agra-Wool International
• Part of the Speedgrow Earthwool growing media range
• Mineral fibre substrate manufactured from basalt
• ECOSE organic binder technology
• Open fibre structure encourages root development
• Excellent balance between moisture retention and aeration
• Provides additional rooting volume after propagation
• Suitable for seedlings and rooted cuttings
• Compatible with 38 x 35mm propagation plugs
• Designed for controlled nutrient management
• Suitable for hydroponic and professional horticultural applications
• Lightweight and easy to handle
• Can progress into larger grow blocks or slabs

From Propagation Plug to Established Plant

One of the primary purposes of the Speedgrow 75mm cube is to provide an intermediate rooting stage between a small propagation plug and a larger growing system.

A typical progression is:

Seed or Cutting → Propagation Plug → 75mm Speedgrow Cube → Grow Block, Slab or Final Growing System

Once roots are established in a compatible propagation plug, the complete plug can be inserted into the 38 x 35mm opening.

This means there is no need to remove the young plant from its existing propagation media and unnecessarily disturb its developing root system.

Roots can instead continue growing outward from the original plug and into the larger Speedgrow block.

Large 38 x 35mm Planting Hole

This version features the large-hole configuration.

Hole Dimensions

Diameter: 38mm
Depth: 35mm

Speedgrow also manufactures smaller-hole blocks, so checking the hole specification is important when matching starter cubes with propagation plugs.

The 38 x 35mm version is particularly useful when transplanting compatible larger propagation plugs into the block.

Earthwool Growing Media

Speedgrow blocks are manufactured from Earthwool mineral fibre, produced using basalt-based mineral material formed into fine fibres.

The resulting structure provides a combination of:

Water retention + drainage + root-zone aeration

Unlike a conventional potting mix, the mineral substrate itself gives the grower a high degree of control over the water and nutrients supplied to the plant.

This makes mineral fibre blocks particularly useful for hydroponic cultivation and other controlled feeding systems.

Open Structure for Root Development

A successful propagation substrate needs to hold sufficient moisture without eliminating the air spaces required by developing roots.

Speedgrow's open fibre structure is designed to provide both.

As roots move through the block, the mineral fibres provide minimal physical resistance while retaining moisture and maintaining air-filled pore space throughout the root zone.

This makes the cube suitable for developing a dense root system before the plant progresses into its final growing environment.

ECOSE Binder Technology

Speedgrow Earthwool uses ECOSE binder technology rather than a conventional binder system.

The binder is based predominantly on naturally derived organic raw materials and holds the mineral fibres together to create a stable propagation block.

This is one of the distinguishing characteristics of the Speedgrow Earthwool range.

Designed for Controlled Feeding

Mineral fibre growing media allows growers to control what reaches the root zone through the irrigation solution.

This can make it easier to manage:

• Nutrient concentration
• Root-zone moisture
• Irrigation frequency
• pH
• EC
• Dry-back
• Fertigation strategy

The block therefore works particularly well in cultivation systems where precise root-zone management is important.

Specifications

How to Use Speedgrow 75mm Propagation Cubes

1. Prepare the Cube

Wet the block evenly before transplanting.

The aim is to achieve consistent moisture throughout the cube rather than leaving dry areas within the substrate.

2. Insert the Propagation Plug

Place the established propagation plug into the 38 x 35mm hole.

The plug should sit securely without being compressed or forced into the opening.

3. Allow Roots to Establish

Maintain appropriate moisture and environmental conditions while the roots expand from the original plug into the surrounding Earthwool.

Avoid repeatedly saturating the block simply because the upper surface appears dry. Root-zone moisture should guide irrigation decisions.

4. Begin Controlled Feeding

Introduce an appropriate nutrient program according to crop requirements and the stage of plant development.

Monitor nutrient strength and pH according to the requirements of your crop and cultivation method.

5. Transplant or Grow On

Once the cube has developed a strong root system, it can be moved into the next stage of the growing system.

Depending on the setup, this may include:

• Larger Speedgrow grow blocks
• Hydroponic slabs
• Drip irrigation systems
• Flood and drain systems
• Larger containers
• Other compatible hydroponic growing media

Ideal for Hydroponic Propagation

The 75mm Speedgrow cube is particularly useful for growers who want more root volume before placing a plant into its final hydroponic system.

Applications can include:

• Hydroponic propagation
• Indoor horticulture
• Greenhouse propagation
• Drip irrigation
• Fertigation
• Nursery production
• Seedling establishment
• Rooted cuttings
• Vegetative establishment
• Mineral fibre slab systems

75mm Cube vs Small Propagation Plug

A small propagation plug is ideal for germination and initial rooting, but its limited volume eventually restricts further root expansion.

The 75mm Speedgrow cube provides the next step.

The young plant remains inside its original plug while the surrounding block provides substantially more substrate for root development.

This staged approach allows growers to use space efficiently during early propagation before increasing the root-zone volume as each plant develops.

Why Choose the 38 x 35mm Hole?

The larger hole is particularly useful when your propagation system already uses 38mm-class plugs.

Instead of attempting to fit a larger plug into a small planting hole, the appropriately sized opening allows the propagation plug to transfer directly into the block.

For growers standardising a propagation system, matching plug and starter-block sizes can make transplanting faster and more consistent.

Why Choose Speedgrow Propagation Cubes?

Speedgrow combines the control associated with mineral fibre cultivation with a modern Earthwool manufacturing process.

The 75 x 75 x 65mm large-hole block is particularly useful as an intermediate stage because it gives developing plants additional rooting volume without immediately moving them into a large block or final container.

For growers already using Speedgrow 38mm propagation plugs, the matching 38 x 35mm hole also creates a straightforward plug-to-block progression.

Frequently Asked Questions

What size is this Speedgrow cube?

The block measures 75mm long x 75mm wide x 65mm high.

What size is the planting hole?

The large planting hole measures approximately 38mm in diameter x 35mm deep.

Is this rockwool?

Speedgrow describes its growing medium as Earthwool, a mineral fibre substrate produced using basalt-based mineral material and ECOSE binder technology. It performs the same general horticultural role commonly associated with stone wool or rockwool growing blocks.

Who manufactures Speedgrow?

Speedgrow is manufactured by Agra-Wool International.

What fits into the 38 x 35mm hole?

It is designed for compatible larger propagation plugs, including 38 x 35mm Speedgrow plug formats.

Can I put a rooted cutting in the cube?

Yes. The block is suitable for young rooted plants and cuttings, particularly where the cutting has first established in a compatible propagation plug.

Can seedlings be used?

Yes. Seedlings established in a compatible plug can be transplanted into the 75mm block for further root development.

Is the cube reusable?

Mineral fibre blocks are primarily intended as growing media for an individual crop cycle. Whether reuse is practical depends on root contamination, sanitation and the intended application.

Can I use the cube in hydroponics?

Yes. Controlled hydroponic cultivation is one of the primary applications for this style of mineral fibre growing block.

Does it contain nutrients?

Treat the block as a controlled growing substrate rather than a complete fertiliser program. Once plants require feeding, provide an appropriate nutrient solution according to crop requirements.

Can I place it on a larger grow block?

Yes. Once sufficiently rooted, the starter block can be incorporated into a larger compatible mineral fibre growing system.

Can it be used on a slab?

Yes. Starter blocks of this type are commonly used as an intermediate propagation stage before plants are established onto larger mineral fibre slabs.

Should I remove the propagation plug before transplanting?

No. A major advantage of using compatible plugs and starter blocks is that the entire rooted propagation plug can be transferred into the cube, helping minimise root disturbance.

Speedgrow 75 x 75 x 65mm Propagation Cube – 38 x 35mm Large Hole Earthwool Starter Block

The Speedgrow 75 x 75 x 65mm Propagation Cube with 38 x 35mm hole is a professional-grade Earthwool starter block designed for seedlings, rooted cuttings and young plants moving from propagation into the next stage of growth.

Manufactured by Agra-Wool International, the Speedgrow range uses mineral fibres produced from basalt and bonded using ECOSE technology, an organic binder technology designed to create an open, root-friendly growing structure.

The generous 38mm diameter x 35mm deep planting hole is designed to accept larger propagation plugs, including compatible 38 x 35mm Speedgrow plugs, allowing young plants to be transplanted into a larger rooting volume with minimal disturbance.

With a compact 75 x 75 x 65mm format, this cube provides considerably more root space than a propagation plug while remaining small enough for efficient nursery, hydroponic and controlled-environment growing applications.

Key Features

• 75 x 75 x 65mm propagation/start block
• Large 38mm diameter x 35mm deep hole
• Manufactured by Agra-Wool International
• Part of the Speedgrow Earthwool growing media range
• Mineral fibre substrate manufactured from basalt
• ECOSE organic binder technology
• Open fibre structure encourages root development
• Excellent balance between moisture retention and aeration
• Provides additional rooting volume after propagation
• Suitable for seedlings and rooted cuttings
• Compatible with 38 x 35mm propagation plugs
• Designed for controlled nutrient management
• Suitable for hydroponic and professional horticultural applications
• Lightweight and easy to handle
• Can progress into larger grow blocks or slabs

From Propagation Plug to Established Plant

One of the primary purposes of the Speedgrow 75mm cube is to provide an intermediate rooting stage between a small propagation plug and a larger growing system.

A typical progression is:

Seed or Cutting → Propagation Plug → 75mm Speedgrow Cube → Grow Block, Slab or Final Growing System

Once roots are established in a compatible propagation plug, the complete plug can be inserted into the 38 x 35mm opening.

This means there is no need to remove the young plant from its existing propagation media and unnecessarily disturb its developing root system.

Roots can instead continue growing outward from the original plug and into the larger Speedgrow block.

Large 38 x 35mm Planting Hole

This version features the large-hole configuration.

Hole Dimensions

Diameter: 38mm
Depth: 35mm

Speedgrow also manufactures smaller-hole blocks, so checking the hole specification is important when matching starter cubes with propagation plugs.

The 38 x 35mm version is particularly useful when transplanting compatible larger propagation plugs into the block.

Earthwool Growing Media

Speedgrow blocks are manufactured from Earthwool mineral fibre, produced using basalt-based mineral material formed into fine fibres.

The resulting structure provides a combination of:

Water retention + drainage + root-zone aeration

Unlike a conventional potting mix, the mineral substrate itself gives the grower a high degree of control over the water and nutrients supplied to the plant.

This makes mineral fibre blocks particularly useful for hydroponic cultivation and other controlled feeding systems.

Open Structure for Root Development

A successful propagation substrate needs to hold sufficient moisture without eliminating the air spaces required by developing roots.

Speedgrow's open fibre structure is designed to provide both.

As roots move through the block, the mineral fibres provide minimal physical resistance while retaining moisture and maintaining air-filled pore space throughout the root zone.

This makes the cube suitable for developing a dense root system before the plant progresses into its final growing environment.

ECOSE Binder Technology

Speedgrow Earthwool uses ECOSE binder technology rather than a conventional binder system.

The binder is based predominantly on naturally derived organic raw materials and holds the mineral fibres together to create a stable propagation block.

This is one of the distinguishing characteristics of the Speedgrow Earthwool range.

Designed for Controlled Feeding

Mineral fibre growing media allows growers to control what reaches the root zone through the irrigation solution.

This can make it easier to manage:

• Nutrient concentration
• Root-zone moisture
• Irrigation frequency
• pH
• EC
• Dry-back
• Fertigation strategy

The block therefore works particularly well in cultivation systems where precise root-zone management is important.

Specifications

How to Use Speedgrow 75mm Propagation Cubes

1. Prepare the Cube

Wet the block evenly before transplanting.

The aim is to achieve consistent moisture throughout the cube rather than leaving dry areas within the substrate.

2. Insert the Propagation Plug

Place the established propagation plug into the 38 x 35mm hole.

The plug should sit securely without being compressed or forced into the opening.

3. Allow Roots to Establish

Maintain appropriate moisture and environmental conditions while the roots expand from the original plug into the surrounding Earthwool.

Avoid repeatedly saturating the block simply because the upper surface appears dry. Root-zone moisture should guide irrigation decisions.

4. Begin Controlled Feeding

Introduce an appropriate nutrient program according to crop requirements and the stage of plant development.

Monitor nutrient strength and pH according to the requirements of your crop and cultivation method.

5. Transplant or Grow On

Once the cube has developed a strong root system, it can be moved into the next stage of the growing system.

Depending on the setup, this may include:

• Larger Speedgrow grow blocks
• Hydroponic slabs
• Drip irrigation systems
• Flood and drain systems
• Larger containers
• Other compatible hydroponic growing media

Ideal for Hydroponic Propagation

The 75mm Speedgrow cube is particularly useful for growers who want more root volume before placing a plant into its final hydroponic system.

Applications can include:

• Hydroponic propagation
• Indoor horticulture
• Greenhouse propagation
• Drip irrigation
• Fertigation
• Nursery production
• Seedling establishment
• Rooted cuttings
• Vegetative establishment
• Mineral fibre slab systems

75mm Cube vs Small Propagation Plug

A small propagation plug is ideal for germination and initial rooting, but its limited volume eventually restricts further root expansion.

The 75mm Speedgrow cube provides the next step.

The young plant remains inside its original plug while the surrounding block provides substantially more substrate for root development.

This staged approach allows growers to use space efficiently during early propagation before increasing the root-zone volume as each plant develops.

Why Choose the 38 x 35mm Hole?

The larger hole is particularly useful when your propagation system already uses 38mm-class plugs.

Instead of attempting to fit a larger plug into a small planting hole, the appropriately sized opening allows the propagation plug to transfer directly into the block.

For growers standardising a propagation system, matching plug and starter-block sizes can make transplanting faster and more consistent.

Why Choose Speedgrow Propagation Cubes?

Speedgrow combines the control associated with mineral fibre cultivation with a modern Earthwool manufacturing process.

The 75 x 75 x 65mm large-hole block is particularly useful as an intermediate stage because it gives developing plants additional rooting volume without immediately moving them into a large block or final container.

For growers already using Speedgrow 38mm propagation plugs, the matching 38 x 35mm hole also creates a straightforward plug-to-block progression.

Frequently Asked Questions

What size is this Speedgrow cube?

The block measures 75mm long x 75mm wide x 65mm high.

What size is the planting hole?

The large planting hole measures approximately 38mm in diameter x 35mm deep.

Is this rockwool?

Speedgrow describes its growing medium as Earthwool, a mineral fibre substrate produced using basalt-based mineral material and ECOSE binder technology. It performs the same general horticultural role commonly associated with stone wool or rockwool growing blocks.

Who manufactures Speedgrow?

Speedgrow is manufactured by Agra-Wool International.

What fits into the 38 x 35mm hole?

It is designed for compatible larger propagation plugs, including 38 x 35mm Speedgrow plug formats.

Can I put a rooted cutting in the cube?

Yes. The block is suitable for young rooted plants and cuttings, particularly where the cutting has first established in a compatible propagation plug.

Can seedlings be used?

Yes. Seedlings established in a compatible plug can be transplanted into the 75mm block for further root development.

Is the cube reusable?

Mineral fibre blocks are primarily intended as growing media for an individual crop cycle. Whether reuse is practical depends on root contamination, sanitation and the intended application.

Can I use the cube in hydroponics?

Yes. Controlled hydroponic cultivation is one of the primary applications for this style of mineral fibre growing block.

Does it contain nutrients?

Treat the block as a controlled growing substrate rather than a complete fertiliser program. Once plants require feeding, provide an appropriate nutrient solution according to crop requirements.

Can I place it on a larger grow block?

Yes. Once sufficiently rooted, the starter block can be incorporated into a larger compatible mineral fibre growing system.

Can it be used on a slab?

Yes. Starter blocks of this type are commonly used as an intermediate propagation stage before plants are established onto larger mineral fibre slabs.

Should I remove the propagation plug before transplanting?

No. A major advantage of using compatible plugs and starter blocks is that the entire rooted propagation plug can be transferred into the cube, helping minimise root disturbance.