Cultivation supplies
by Unicorn Bags
The Mushroom Spawn Bag with Injection Port is a sterile, autoclavable polypropylene bag designed to give your mushroom spores or liquid culture the cleanest possible environment to colonise substrate. Made by Unicorn Bags — the name most growers recognise in the cultivation supply world — these bags come in two sizes (T4 and T10) and feature Tyvek filter patches with the smallest pore size available, keeping contaminants out while letting your mycelium breathe. If you've ever lost a batch to mould or bacteria sneaking in through a dodgy seal, you already know why a proper spawn bag matters.
Both bags are built from the same 3.0 mil polypropylene and use identical Tyvek filter ports. The difference is capacity, and picking the right one depends on how much substrate you're working with per batch.
| Spec | T4 (SH0136) | T10 (SH0137) |
|---|---|---|
| Dimensions | 10 x 7.5 x 45 cm | 12 x 10 x 45 cm |
| Substrate capacity | Just under 1 kg | Approximately 2 kg |
| Filter type | Tyvek (smallest pore size) | Tyvek (smallest pore size) |
| Material thickness | 3.0 mil polypropylene | 3.0 mil polypropylene |
| Autoclave safe | Yes — up to 120°C | Yes — up to 120°C |
| Reusable | Yes | Yes |
The T4 is your go-to for single-strain small runs or if you're working in a tight space — a cupboard, a small shelf, a corner of the spare room. Under 1 kg of substrate fits neatly, and the smaller footprint means you can run several bags side by side without them crowding each other.
The T10 doubles your capacity to around 2 kg of substrate, which means faster colonisation across a larger volume and — ultimately — a bigger yield per bag. If you already know what you're doing and want fewer bags to manage per cycle, the T10 saves time. We'd pick the T10 for anything beyond a first experiment, honestly. The extra substrate volume gives mycelium more room to establish before fruiting, and that usually translates to healthier flushes.
| Spec | Value |
|---|---|
| Brand | Unicorn Bags |
| Material | 3.0 mil polypropylene |
| Filter type | Tyvek (T) — smallest pore size |
| Injection port | Self-healing, airtight seal |
| Autoclave rating | Up to 120°C / steam sterilisation |
| Reusable | Yes |
| T4 dimensions | 10 x 7.5 x 45 cm |
| T4 capacity | ~1 kg substrate |
| T10 dimensions | 12 x 10 x 45 cm |
| T10 capacity | ~2 kg substrate |
| SKU (T4) | SH0136 |
| SKU (T10) | SH0137 |
Complete your cultivation setup: pair these spawn bags with a Spore Syringe for inoculation and a Magic Mushroom Grow Kit if you want a side-by-side comparison between bag cultivation and an all-in-one kit. A Still Air Box or laminar flow hood will also dramatically cut your contamination risk during inoculation.
We've been selling grow supplies since 1999, and the single biggest reason people fail at home cultivation hasn't changed in 25 years: contamination. One ungloved finger, one sneeze near an open jar, one bag that wasn't properly sealed — and you're watching green mould eat your mycelium instead of the other way around. It's demoralising, and it's almost always preventable.
The Mushroom Spawn Bag with Injection Port tackles this head-on. The Tyvek filter patch allows gas exchange (your mycelium needs to breathe) while blocking airborne contaminants. The injection port creates an airtight seal the moment you pull your syringe out — no fumbling with micropore tape, no exposed substrate. You load your grain or substrate, autoclave the entire bag at up to 120°C to sterilise it, let it cool, inject your spores or liquid culture through the port, and walk away. The bag does the rest.
The honest limitation? These bags don't come with substrate or spores — you need to source those separately. And while the bags themselves are reusable after autoclaving, the injection port can only take so many punctures before the self-healing seal starts to weaken. We'd say 2-3 uses per bag is realistic before you want a fresh one. Still, at this price point, that's not exactly a hardship.
Grain jars work, but they're heavy, breakable, and a pain to sterilise in bulk. Monotubs are great for fruiting but not designed for the colonisation stage. A mushroom spawn bag sits in the sweet spot: lightweight, autoclavable, self-sealing, and collapsible for storage. You can stack a dozen in a cupboard and barely notice them. Try that with mason jars.
Compared to cheaper no-name bags, Unicorn Bags have earned their reputation for a reason. The 3.0 mil polypropylene feels noticeably thicker in hand — there's a stiffness to it that cheaper bags lack, which matters when you're handling a bag full of hot, wet substrate fresh out of a pressure cooker. Thin bags tear. These don't. The Tyvek filter is also a step above the synthetic filter patches you'll find on budget alternatives — tighter pore size means better contamination resistance.
The question we get most about spawn bags: "Can I skip the pressure cooker?" Short answer — no. Not if you want consistent results. Some people try steam sterilisation in a stock pot with a loose lid, and it works sometimes, but "sometimes" isn't what you want when you've spent weeks waiting for colonisation. A proper pressure cooker hitting 120°C at 15 PSI is the standard for a reason. If you're serious about growing, it's the single best investment after the bags themselves.
One more thing we've noticed over the years: people tend to over-inoculate. More spores doesn't mean faster colonisation — it means more moisture inside the bag, which can actually slow things down or create conditions for bacterial contamination. Stick to 2-4 cc per bag. Less is more here.
Yes. These Unicorn spawn bags work with any species that colonises grain or supplemented sawdust substrate — from oyster mushrooms to cubensis strains. The Tyvek filter and polypropylene construction are species-agnostic. Just match your substrate to the species you're growing.
The T stands for Tyvek, which is the filter material used on the bag's gas exchange patch. Tyvek filters have the smallest pore size available in Unicorn's range, providing the tightest contamination barrier while still allowing enough air exchange for healthy mycelial growth.
The bags withstand autoclaving and are technically reusable. Realistically, expect 2-3 cycles before the injection port's self-healing seal starts to degrade. The polypropylene itself holds up well, but the port is the weak point after repeated punctures.
Not strictly, but it helps enormously. The injection port minimises exposure compared to open-air transfers, so a Still Air Box (a plastic tub with arm holes) is a solid budget alternative. Work quickly, wipe the port with alcohol, and you'll be fine in most home environments.
For the T4 (approximately 1 kg capacity), 2 cc of spore solution or liquid culture is sufficient. For the T10 (approximately 2 kg), 3-4 cc works well. Move the needle around inside the bag as you inject to distribute the solution evenly across the substrate.
Yes. The 3.0 mil polypropylene is rated for steam sterilisation up to 120°C, which is exactly what a standard 15 PSI pressure cooker reaches. Run them for 60-90 minutes depending on substrate volume. Just make sure the bags aren't pressed directly against the cooker walls — use a trivet or rack.
Rye grain and wild bird seed are the two most popular choices for spawn production. Some growers use brown rice flour for smaller runs. The bag itself is just the vessel — match your substrate to your mushroom species and preferred tek. Grain spawn in these bags can later be transferred to bulk substrates like coco coir or straw.
Last updated: April 2026
Medical disclaimer. This content is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before use of any substance.
