Instead of using jars or bottles, many mushroom growers prefer to use spawn bags instead. A spawn bag is a polypropylene bag fitted with 0.2 – 0.5 micron filter on it for air exchange. Spawn bags make a lot of sense when you are growing mushrooms because the bags can hold a large volume, easily be sterilized, and can be discarded after use.

Spawn bags are cheap and efficient and allow for a wide range of activities. Some people run their whole process from spawn bags, while others only use them for certain steps. The biggest downside to using them at all is their waste. The bag are non-biodegradable and are non-recyclable in most areas.

What Kind of Spawn Bags are Best?

There are a lot of different kinds of spawn bags out there, but you need to get the right ones. First and foremost you need to get bags with 0.5 micron filters or smaller. Some bags have larger filter pores and these are less effective at stopping contamination. Be sure to check before you purchase.

The next thing you need to look at is the material. You want the bags to be made out of polypropylene. There are a few reasons for this, but most important is that polypropylene can be sterilized in an autoclave or pressure cooker without melting. When checking the material also make sure the thickness is correct. You want 3 mil polypropylene typically for durability.

Spawn bags also come in many sizes. My personal recommendation is that it is better to have more small bags than it is to have fewer larger ones. This makes it easier to fruit your blocks and helps cut down on contamination issues. The additional surface area you get for having more small bags also helps speed up the growing process slightly, though it more work to inoculate more bags.

If you do end up getting larger bags, make sure you get ones that are longer and taller. This will mean there are more areas for you to fruit mushrooms from. This also makes it easier to hang your bags if that is your preferred way to fruit them.

Where Can I Get Spawn Bags

Unfortunately most stores won’t have spawn bags for you to pickup. In most cases you will have to purchase these online. Since mushroom farming is becoming a more and more popular hobby, spawn bags have become more easily available online.

A pack of 50 spawn bags with 0.5 micro filters on them can be purchased on amazon for less then $40. This is insanely cheap and makes most home growing operations viable and cost effective. These bags make roughly 8lb blocks when packed.

Pack of 50 Spawn Bags with 0.5 micron filters

Using Spawn Bags

If you decide to use spawn bags over grow bottles, you’ll need at least one more piece of equipment: an impulse sealer. This is a heat sealing device that will help you seal your bags to prevent contamination.

Many people will tell you to seal your bags before you sterilize them and then inject your liquid culture into the bags. This is wrong for multiple reasons. First, sealed bags can rupture in an pressure cooker making them worthless. Second, you should never inject through a bad without an injection port, it opens the bag up to contamination. Instead tape your bags shut with autoclave tape for sterilization. You can seal them after they are inoculated in a clean area, like a glovebox or flow hood.

Spawn Bags and Your Setup

Spawn bags are best used when you are scaling up your home cultivation efforts, and why wouldn’t you? Even though they do present some waste problems, they are the cheapest and most efficient way to get a lot of mushrooms going at once. Everyone should try using spawn bags at least once and see if they make sense for your home setup.