Cultiwool CRB Propagator Plugs — Commercial-Grade Rockwool Starter Cubes for Seedlings and Cuttings
Best for: Growers starting seeds or rooting cuttings who want reliable, uniform propagation without faffing about
Our thoughts
Cultiwool CRB plugs are the workhorse of propagation. Made in the Netherlands to commercial standards, they give seedlings and cuttings exactly what they need — consistent moisture, proper aeration, and a clean environment to develop strong roots. One we sell a lot of for growers scaling up their propagation game.
Cultiwool CRB propagator plugs are compressed stone wool starter cubes designed to give your cuttings and seedlings the very best start in life. Made from high-quality, inert rockwool, they provide a sterile growing environment with no harmful bacteria or contaminants. The plugs balance water retention and aeration perfectly, allowing roots to develop strong and fast — then transplant seamlessly into larger Cultiwool growing cubes or your chosen hydroponic system. It's propagation media that actually does the job.
How it compares
Cultiwool CRB sits in the commercial-grade, affordable bracket of propagation plugs.
- Same reliability as premium brands like Grodan at a lower price point
- Superior to organic alternatives (Rapid Rooter, etc.) for hydroponic consistency
- Better air-to-water ratio than loose rockwool or peat-based alternatives
- Fits neatly into Cultiwool grow blocks for seamless system progression
In short: you get commercial-standard propagation without paying commercial-standard money.
Usage guidance
Preparing your plugs
Soak your Cultiwool plugs in your chosen nutrient solution (pH 5.5–6.5 works well). Let them absorb fully — they should feel saturated but not waterlogged.
Seeding
Drop 1–3 seeds into the centre of each plug and push them down 1–2 inches. Keep them in darkness until germination occurs, then bring into light as required.
Rooting cuttings
Insert cuttings into the pre-slit centre and keep moisture consistent. Rockwool holds water at the base, so roots always have access to what they need.
Transplanting
After 3–4 true leaves appear, the plug drops straight into a larger Cultiwool cube or into soil/coco. No handling damage, no transplant shock — the whole plug moves with the plant.
Technical specifications
- Material: High-quality compressed stone wool (rockwool)
- Available sizes: 25mm × 25mm × 40mm tall or 36mm × 36mm × 40mm tall
- Composition: Inert, sterile, no harmful contaminants
- Air-to-water ratio: Optimised for balanced moisture and aeration
- pH: Neutral (adjusts to your nutrient solution)
- EC: Nil (inert medium)
- Packaging: Available in 2,700-plug boxes or smaller individual trays (150 plugs)
- Design: Pre-slit centre for easy seed/cutting insertion
- Manufacturing: Netherlands
Who this is for
- Growers scaling up from random propagation methods to a proper system
- Hydroponic growers building complete Cultiwool setups
- Commercial propagators or anyone running multiple batches
- Seedling and cutting propagators who want consistency without guessing
- Growers who need high-density propagation in limited space
Particularly well suited to anyone who wants reliable, uniform results across dozens or hundreds of plugs at once.
Our take
These are proper propagation plugs — clean, consistent, and engineered to do one job well. The water pools at the base, air flows through the structure, roots develop strong, and transplanting is stress-free. That's exactly what you want from starter media.
Good time to buy while clearance stock lasts. Worth picking up if you're building a propagation setup or scaling one you've already got running.
