What You Need To Know About Spawn Bags & Jars
So you have started your research into mushroom growing and you have heard about mushroom grow bags and spawn jars. But what are they really? And how do they stack up against each other?
What is a Mushroom Grow Bag?
A mushroom grow bag is designed for growing mushrooms. Many kinds of mushrooms can be grown in a bag, but it depends on what type of substrate is put in the bag. There are several brands and types, but all good grow bags have several features in common.
Features of mushroom grow bags:
- Polypropylene - Grow bags are made of polypropylene plastic designed to withstand high temperatures. The plastic is durable, flexible, clear enough to make monitoring growth easy, and relatively low-cost. Some bags are being developed using “greener” materials, but none have been able to withstand pressure sterilization. Which brings us to the next feature:
- Autoclavable - The reason temperature resistance is essential is that both the substrate and the inside of the bag must be sterilized before inoculation. A convenient sterilization method is to stick the bag and its contents in an autoclave—except that most plastic bags would melt in such conditions. “Autoclavable” just means that the bag can be safely used in an autoclave. An autoclave is a machine that uses steam under pressure to kill bacteria. Many beginners use pressure cookers as a cheaper alternative, as they can be easily adapted to achieve similar conditions.
- Filter Patch - A filter patch is a small bag area that allows air through a fine mesh. The mesh is constructed with pores small enough that airborne bacteria and the spores of unwanted fungal species (weeds) can’t get through. Unlike a vegetable garden, a mushroom set-up can’t be weeded; the weeds must be kept out from the beginning, or the batch must be abandoned. Mushroom grow bags need filter patches because while it is vital to keep out weeds, the mycelium must be able to breathe (another thing, besides the need for food, that fungi have in common with animals).
Why Use Mushroom Grow bags?
It’s possible to grow mushrooms without bags. Of course, some substrates, such as logs, don’t need and can’t fit in bags. However, even substrates often used with bags, such as coffee grounds or sawdust, don’t require them. Alternatives include wide-mouth glass jars and plastic buckets and tubs (these are sometimes available from restaurants at no cost), provided the containers in question can be sterilized and fitted with air filters.
There are also low-temperature sterilization methods and ways to grow mushrooms that don’t require sterilization at all—such methods dramatically broaden the range of set-ups that can be used.
Some growers seek to grow bags specifically to prevent plastic waste since the bags are generally single-use. While this may be true on the surface level, there are hundreds of fungal species that consume plastic, including oyster mushrooms. In addition, there are also oxo-biodegradable bags on the market that can break down in any environment; an excellent insurance policy against plastic waste.
Grow bags offer certain features that are difficult to access otherwise:
- It’s easy to cut holes in a bag, allowing the fungus to fruit out in all directions instead of just upwards. But it’s different for a glass.
- The clear plastic makes it easy to monitor the mycelium as it colonizes the substrate. With buckets, it’s harder to tell when colonization is complete and when the fungus is ready to fruit.
- In spawn bags, the spent substrate—or the fully colonized spawn—is easy to remove from a bag. Because the mycelium tends to hold the substrate together in a clump, getting the clump out of a jar or even a bucket can be a real challenge.
- The flexible bag makes it easy to mix the spawn thoroughly through the substrate; just squeeze. The same can’t be said of a hard-sized container.
- Start-up costs are low, even for large operations, since bags are cheap.
Growing With Glass Jars
Everyone knows that mushroom growing bags work great. But unless opting for biodegradable bags, these one-use Polypropylene (PP) or High-Density Polyethylene (HDPE) bags are far from the most environmentally friendly way to grow unless the grower also has a plastic eating mushroom compost. Luckily, growers can grow their mushrooms in small, reusable bottles.
Why Grow In Bottles?
Growing in bottles isn’t a new concept.
In Japan, cultivators have been using bottle culture techniques for decades, and the popularity also seems to be rising in the USA. That’s probably because these methods provide several distinct advantages.Better For The Environment
Mushroom grow bags are one-use only, requiring a dedicated space for a compost with specialized plastic eating fungi. Bottles, on the other hand, can be used over and over for several years. Growers are always trying to develop ways to produce less waste, such as re-suing bags or even using containers like 5-gallon buckets. Unfortunately, none of these methods work nearly as well growing in bottles.Mechanization
This won’t impact home growers or small-scale farmers, but large-scale operations can see considerable improvements in efficiency and labor costs through the mechanization offered by bottle growing.Consistency
Growing mushrooms in bottles can result in highly uniform fruits, making it easier to harvest, package, and market your mushrooms. When grown this way, they are also quite suitable for shipping to long distances and sold into other markets.
Admittedly, these are some pretty HUGE advantages. It sounds like a no-brainer, right?
Well, before you jump over to Ali-Baba and start ordering your machines, you might want to consider some of the disadvantages of bottle culture.Species Are Limited
While not all mushrooms can be cultivated in bottles, some of them can be grown in bags.High Start-Up Costs
The costs associated with starting a bottle mushroom farm are sky-high. It requires several expensive machines, plus the outrageous initial cost of all the bottles.
This could easily add up to several hundred thousand dollars. In other words, you’d better have some serious cash and be quite sure of the market before starting this kind of operation.
On the other hand, bag cultivation can be started on a tiny scale- all you need is a small pressure cooker and some relatively cheap grow bags!
Bottle cultures typically produce smaller fruit bodies than those grown in bags.
Maitake, for example, can be grown in both bottles and bags. However, the Maitake clusters or “fronds” will be more significant when using the bag method, and the overall yield will also likely be higher.Slower Colonization Times
Compared to bags, it generally takes much longer for bottles to colonize before fruiting. This is because bags can be thoroughly mixed after colonization. In contrast, the bottles are inoculated by pouring spawn or liquid culture in the center of the substrate (usually in an open hole) and cannot be mixed without risking breaking the jar.Single Flush
When grown in bottles, the mushrooms are usually only harvested once, with no second flush. This is because the amount of substrate does not support a significant second flush, and it is found to be not worth pursuing in most cases.
Have you made your choice yet? If your choice is bags, then we’re cooking with gas! We‘re the number one source for mushroom grow bags. Check out our collection here and if you need you can look at our tutorials here.