Plagron Growmix 50L — Pre-Fertilised Peat Substrate Ready to Grow
Best for: Growers who want a proper growing medium with nutrients already built in, so you're not second-guessing feeding schedules for the first three weeks
Our thoughts
This is the middle ground done right. You get a quality peat-based substrate pre-loaded with nutrients for three weeks, plus worm castings for biological activity and perlite for breathing room. No overthinking, no starvation phase, no guesswork. One we recommend a lot for growers who want a solid foundation without the faffing.
Plagron Growmix is a ready-to-use growing medium built from a blend of white peat, black peat, fibrous peat, perlite, and Plagron worm castings. It arrives pre-fertilised with a balanced NPK formulation (12-14-24) that keeps plants fed for the first three weeks of growth, giving you a clean entry point into the growing cycle. The worm castings boost biological activity without you having to think about it, whilst the perlite ensures the medium stays light and aerated—essential in UK conditions where moisture can be a problem. This is the sweet spot between basic peat and over-complicated mixes.
How it compares
Growmix sits right in the middle of the Plagron range—and that's the point.
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vs. Lightmix: Lightmix feeds for one week only; Growmix gives you three weeks. If you want fewer early feeding decisions, Growmix wins.
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vs. Allmix: Allmix is pre-fertilised for six weeks and certified organic. Growmix is shorter-window, non-organic, and leaves you room to adjust feeding earlier if needed.
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vs. Coco alternatives: Peat-based means it holds moisture better than coco and is more forgiving for beginners. Works best with standard nutrients from week three onwards.
In short: more control than Allmix, more nutrition than Lightmix, more familiar than coco.
Usage guidance
Growmix is designed for potting and re-potting, right through the growing cycle.
Weeks 1–3
Use straight from the bag. Water as normal. The pre-loaded nutrients do the work. Don't feed yet—you'll overshoot.
Week 3 onwards
Begin your normal feeding schedule. Plagron Terra Grow (vegetative phase) and Terra Bloom (flowering phase) work best, but any balanced nutrient will do. The medium is neutral enough that you're in control from here.
Water retention and drainage
The perlite keeps it fluffy; the peat holds moisture. You won't get waterlogging, but you won't have coco-level drain-through either. Let the top inch dry between waterings—standard practice.
Common mixing practice
Some experienced growers blend Growmix 50/50 with Allmix for larger crops, balancing cost and nutrient window. Works cleanly.
Technical specifications
- Volume: 50 litres per bag
- Composition: White peat, black peat, fibrous peat, perlite, Plagron worm castings
- pH: 5.7–6.7 (1:1.5 ratio)
- EC: 1.0–1.7 mS/cm (1:1.5 ratio)
- Pre-fertilisation: 1.8 kg/m³ mineral fertiliser (NPK 12-14-24)
- Nutrient window: 3 weeks
- Pallet quantity: 60 bags
- Dimensions per bag: 67cm H × 36cm W × 25cm D
- Certification: RHP certified
- Available variants: With or without added perlite
Who this is for
- First-time growers who want nutrients sorted for the first month
- Experienced growers scaling up production and buying in bulk (60-bag pallet)
- Anyone tired of deciding between over-fed and under-fed substrates
- Growers in UK climates where peat's moisture retention beats coco's quick drain
- Plagron ecosystem users building a full nutrient lineup
Our take
Growmix nails the three-week goldilocks window. You're not micromanaging nutrition from day one, but you're not locked into six weeks of pre-feed either. The worm castings are a genuine plus—they do real work—and the perlite means it breathes properly in damp conditions.
If you're after a proper peat-based substrate that doesn't require immediate feeding decisions, this is worth picking up. Does exactly what a growing medium should do, and gives you the flexibility to take over from week three. Good time to buy while stock lasts.
