What is insect frass? A straightforward UK guide (and yes, it’s basically insect poo)
“Insect frass” is one of those gardening terms that sounds technical until someone explains it properly. In plain English, frass is the material left behind when insects are reared and fed. When it’s prepared for gardeners, it’s used as a natural fertiliser and soil input because it provides nutrients and organic matter in a practical, easy-to-apply form.
This post explains what frass is, what it isn’t, and why it’s become such a talked-about option for UK gardeners.
What does “frass” actually mean?
“Frass” is simply the name for insect waste. In the context of gardening products, it usually refers to a dry, granular material collected from insect rearing systems.
Exactly what’s in it can vary depending on the insects and how the system is managed, but frass products commonly include:
- insect droppings
- fine organic material from the rearing environment
- small amounts of shed insect skins (a normal part of insect growth)
The important point is this: frass is used in gardens because it’s a stable, manageable way to return natural nutrients and organic matter to soil or compost.
Is insect frass the same as “insect poo”?
More or less — that’s why “insect poo fertiliser” has become a common search phrase.
But most frass sold for gardening isn’t only droppings. It’s typically a blend of waste and fine organic residues from the rearing process. That’s not a bad thing; it’s simply what “frass” usually means in real-world use.
If you’re explaining it to someone at the allotment: yes, it’s basically insect poo — just processed and prepared for gardening.
Is insect frass safe to use in gardens?
For normal home gardening, frass is generally treated like other organic fertilisers: sensible handling and sensible application.
A few commonsense habits go a long way:
- apply to soil/compost, not directly onto leaves
- wash hands after use
- avoid breathing in dust when pouring (especially indoors)
- store it dry and sealed
If you’re using frass around edible crops, it’s also worth keeping it as a soil application rather than something that sits on leaves.
Why do gardeners use insect frass?
Most people choose frass for one of three reasons.
It’s a practical “soil-first” fertiliser
Frass tends to be used for steady, measured feeding rather than dramatic quick fixes. For gardeners who want consistent growth without pushing plants too hard, that’s a feature, not a drawback.
It plays nicely with compost and soil-building
Compost is fantastic for structure and long-term soil health, but its nutrient strength can vary. Frass can sit alongside compost as a more consistent, repeatable input.
It’s tidy and easy to apply
Compared with some traditional organics, frass is often popular simply because it’s clean, easy to measure, and straightforward to store.
If you want the practical “how” (timing, methods, mistakes to avoid), this pairs with:
https://syntects.co.uk/how-to-use-insect-frass-fertiliser
What is insect frass used for?
Frass is most commonly used for:
- pots and containers, where nutrients wash out faster
- vegetable beds and raised beds, alongside compost
- houseplants, where light, careful feeding matters
- borders and ornamentals, as a steady seasonal support
We’ve also covered the broader “what it does” here:
https://syntects.co.uk/what-does-insect-frass-do-for-plants
(If that URL doesn’t exist on your site yet, we’ll publish it to match the blog we just wrote.)
What to look for when buying insect frass fertiliser
Because frass is a category, not a single standardised product, it’s worth looking for:
- clear provenance (who made it, and where)
- consistent texture and dryness (easy to spread, less likely to clump)
- practical usage guidance you can actually follow
- a supplier that talks plainly about what it is (and doesn’t overpromise)
Flytiliser: insect frass for home gardens and bulk use
If you’re looking for an insect frass fertiliser from Syntects, Flytiliser is available in two formats depending on scale:
- Flytiliser (500g): https://syntects.co.uk/product/flytiliser
- Flytiliser (1 ton): https://syntects.co.uk/product/flytiliser-insect-frass-fertiliser-1-ton
For the full overview guide, see:
https://syntects.co.uk/insect-frass-fertiliser-uk-guide
FAQs
Does insect frass smell?
Most gardeners choose it partly because it’s generally easier to handle than some traditional organic fertilisers. Like anything organic, it should be stored dry and sealed.
Can you use insect frass on houseplants?
Yes, but apply lightly and pay attention to light levels (many indoor plants need less feeding in winter). We’ll publish a dedicated indoor guide next.
Is frass a replacement for compost?
Not really. Compost is your structure and soil-building foundation; frass is a more measured fertiliser input that can complement it.






