Fertilizers & nutrients
by Plagron
Plagron Seedbooster Plus is a germination and early growth stimulant that can speed up the sprouting process by up to 40%. Formulated with protease and cellulolytic enzymes alongside sorbus aucuparia extract, this concentrated tonic gives your seeds a fighting chance from day one — and can even breathe new life into older seeds that have been sitting in a drawer for a bit too long. Seven drops per litre of water. That's all it takes.
Plagron Seedbooster Plus addresses the single most frustrating moment in any grow: waiting for your seeds to pop. You've spent good money on genetics, prepared your medium, set up your tent — and then you're just staring at soil for days, wondering if anything's happening down there. This product shortens that anxious window considerably. Plagron claims up to 40% faster germination, and from what we've seen behind the counter over the years, growers who use it tend to report visible shoots within a couple of days rather than the usual four to seven.
The formula contains protease and cellulolytic enzymes that break down the seed coat more efficiently, helping moisture reach the embryo faster. There's also an extract of sorbus aucuparia (rowan berry), which is naturally rich in sorbic acid — a compound that helps protect against mould and bacterial pathogens during that vulnerable pre-sprout phase. When seeds fail, it's often not because the genetics are bad. It's because something got to them first. Seedbooster Plus stacks the deck in your favour.
One honest limitation: this won't resurrect truly dead seeds. If your beans have been stored in heat or humidity for years and the embryo is gone, no stimulant will bring them back. But for seeds that are viable yet sluggish — maybe a year or two old, stored in decent conditions — it genuinely makes a difference. We'd call it cheap insurance for expensive genetics.
The enzymatic action in Plagron Seedbooster Plus targets the seed coat directly. Protease enzymes break down proteins in the outer shell, while cellulolytic enzymes work on the cellulose structure. Together, they soften the seed casing so water penetrates more quickly and evenly. The NPK ratio of 5-4-7 provides a light nutritional boost — just enough to fuel the initial root tip and cotyledon development without overwhelming a tiny seedling.
The sorbus aucuparia extract does double duty. It delivers micronutrients to the emerging root system while its natural antimicrobial properties create a less hospitable environment for the mould spores and bacteria that thrive in warm, moist germination conditions. Think of it as a bodyguard and a lunch box rolled into one.
You can continue using the Seedbooster Plus solution right through until the first true leaves appear. After that, you'd switch to a dedicated root stimulator or vegetative feed. Plagron's own Power Roots is the obvious next step if you're staying within their product line.
| Specification | Detail |
|---|---|
| Brand | Plagron |
| Product type | Germination and early growth stimulant |
| NPK ratio | 5-4-7 |
| Active ingredients | Protease enzymes, cellulolytic enzymes, sorbus aucuparia extract |
| Bottle size | 10 ml |
| Dosage | 7 drops per 1 litre of water |
| Application period | From sowing until first true leaves appear |
| SKU | HS0554 |
Using Plagron Seedbooster Plus is straightforward — the whole bottle lasts a surprisingly long time given you only need 7 drops per litre. The liquid itself is thin and slightly amber-coloured, with a faint earthy smell that's barely noticeable once diluted.
A 10 ml bottle contains roughly 200 drops. At 7 drops per litre, that gives you about 28 litres of working solution — more than enough for dozens of seeds across multiple germination rounds. Store the bottle in a cool, dark place between uses. The cap seals tightly, which helps, but don't leave it on a windowsill baking in the sun.
We've been selling seeds and grow supplies since 1999, and the germination phase is where most first-time growers lose confidence. You plant a seed, nothing happens for three days, and suddenly you're convinced you've done something wrong. Nine times out of ten, the seed is fine — it just needs more time. But that uncertainty is real, and it leads people to dig up seeds to "check on them," which usually kills the taproot. A product like Plagron Seedbooster Plus doesn't just speed things up; it gives you something concrete to do during the wait. You're actively feeding the process rather than just hoping.
The other thing we see a lot: growers with a handful of older seeds from a strain that's been discontinued. Those seeds are irreplaceable, and the germination rate on 2-3 year old beans drops off noticeably. Seedbooster Plus won't guarantee a 100% success rate on old stock, but it tilts the odds. If you've got five seeds left of something special, spending a few quid on a germination stimulant is a no-brainer compared to losing three of them to a slow start and opportunistic mould.
Most growers germinate with nothing more than water and a warm spot. And honestly, that works fine for fresh seeds in good conditions. The question is whether the margin Seedbooster Plus provides is worth it to you. Here's a practical comparison based on what we've observed:
| Factor | Plain water | Plagron Seedbooster Plus |
|---|---|---|
| Typical germination time | 3-7 days | 2-4 days (up to 40% faster) |
| Pathogen protection | None | Antimicrobial sorbus aucuparia extract |
| Nutritional support | None until feeding begins | NPK 5-4-7 from sowing |
| Old seed viability | Hit or miss | Improved — enzyme action softens aged seed coats |
| Cost per litre of solution | Essentially free | Minimal — 7 drops from a 10 ml bottle |
| Ease of use | Just add water | Shake, count 7 drops, done |
If you're popping a single seed of a common strain, plain water is perfectly fine. But if you're running multiple seeds, working with older genetics, or just want the peace of mind that comes with giving your plants every advantage from the start, Seedbooster Plus earns its spot on the shelf.
Once your seedlings show their first true leaves, it's time to switch to a dedicated root stimulator. Plagron Power Roots picks up exactly where Seedbooster Plus leaves off, driving root mass development through the vegetative phase. If you're building a full Plagron feed schedule, pair both with Plagron Alga Grow for a complete organic start.
It can improve germination rates on older seeds that are still viable by softening the aged seed coat with enzymatic action. Truly dead seeds — where the embryo has deteriorated from heat or moisture damage — won't respond to any stimulant. If your seeds are 1-3 years old and were stored in cool, dry conditions, Seedbooster Plus is well worth trying.
At 7 drops per litre, a 10 ml bottle yields roughly 28 litres of working solution. Even if you're watering multiple times during the germination phase, one bottle covers dozens of seeds across several grows. It's one of the most economical germination products available.
Plagron doesn't specify pH adjustment for Seedbooster Plus, and at such a low concentration (7 drops per litre), it has minimal impact on your water's pH. If you're germinating in rockwool, which is pH-sensitive, it's good practice to check — but for soil, coco, or paper towel germination, don't overthink it.
Stop once the first true leaves appear — those are the serrated, pointed leaves, not the initial round cotyledons. At that point, your seedling is ready for a root stimulator or light vegetative feed. Continuing Seedbooster Plus beyond this stage won't harm anything, but it's no longer the right tool for the job.
Yes. It works with soil, coco, rockwool, perlite, and even the paper towel method. The enzymes and nutrients are delivered through the water, so the medium doesn't matter. Just make sure you're using the correct dilution: 7 drops per litre, no more.
Plagron lists it as containing natural enzymes and plant extracts (sorbus aucuparia). However, it also carries an NPK of 5-4-7, and Plagron doesn't market it under their organic line. If you're running a strictly certified organic grow, check the specific certification requirements for your setup.
During the germination phase, Seedbooster Plus is all you need. Adding other nutrients or stimulators at this stage risks overloading a seed that hasn't even developed roots yet. Save the rest of your Plagron lineup — Power Roots, Alga Grow, and so on — for after the first true leaves appear.
Last updated: April 2026
