Plagron Megaworm — 100% Organic Worm Castings Soil Amendment
Best for: Growers building living soil or mixing their own potting blend without breaking the bank on organic amendments
Our thoughts
If you're serious about soil biology but don't want to spend a fortune, Megaworm does the job properly. It's pure worm castings, certified organic, packed with the microbes and enzymes your soil actually needs. One we recommend a lot for growers moving towards organic growing or building their own soil mixes.
Plagron Megaworm is a 100% organic worm castings soil amendment made from composted Dendrobaena Veneta earthworm castings. It works by introducing beneficial microbial activity, trace elements, and natural enzymes into your growing medium — essentially giving your soil a working immune system. Unlike synthetic amendments, Megaworm creates the conditions for plants to feed themselves properly, which is why experienced growers use it as the foundation of any soil-based setup.
How it compares
Megaworm sits in the organic, microbial-focused tier of soil amendments.
- Pure worm castings — no filler, no bulking agents, no shortcuts
- Significantly cheaper per litre than premium branded alternatives
- Lower EC than some competitors, which means less salt buildup risk
- CU-certified organic, so it works in systems where certification matters
- Multiple size options (1L to 25L) — better for small growers than bulk-only competitors
If you're comparing this to BioBizz or other premium worm humus products, the functional difference is negligible. You're paying for the Plagron name and availability, not better biology.
Usage guidance
Megaworm is a solid amendment, not a liquid, so application depends on your setup:
Mixing into potting soil
Add 100–200 litres of Megaworm per 1,000 litres of base potting mix. Start at 10% and adjust upwards based on how your plants respond. No burn risk — you can't overdose on organic matter.
Top dressing
Spread a thin layer (1–2cm) on the surface of established pots and water in. Works well mid-cycle to boost microbial activity without repotting.
Garden or outdoor beds
Use 1 litre per 3–5m² and dig or rake in. The worms are already removed, so it won't migrate — it just sits there feeding your soil.
Important — not for automated systems
Because it's solid and slow-release, don't put this in tanks or dripper systems. It's soil-only. If you're running coco or hydro, this isn't the product.
Technical specifications
- Composition: 100% worm castings (Dendrobaena Veneta earthworm)
- pH: 6.0–7.0
- EC: 1.5 mS/cm
- Active ingredients: Mycorrhiza, Trichoderma, natural enzymes, trace elements
- Form: Powdered organic amendment
- Organic certified: Yes (CU certified)
- Available sizes: 1L, 5L, 10L, 25L
Who this is for
- Growers building their own organic potting mixes and wanting proper soil biology
- Organic-certified operations or those working towards certification
- Anyone moving away from synthetic nutrients towards living soil methods
- Budget-conscious growers who don't want to compromise on soil quality
- Experienced growers who understand soil chemistry and want to dial in their own blends
Less suitable for: hydro growers, dripper systems, or anyone who needs instant nutrient availability.
Our take
This is proper organic soil biology at a sensible price. Megaworm doesn't come with marketing fluff or premium branding — it's just worm castings that do exactly what they should: feed your soil, not your plants. The microbial load is genuine, the pH is stable, and the price leaves room for decent base compost.
If you're building soil or mixing your own potting blend, worth picking up while clearance stock lasts. Does the job, day in, day out.
