In this article, we'll help to demystify exactly what mushroom spawn is and cover some considerations that might sway your choice when growing mushrooms outdoors.
What is mushroom spawn?
Spawn is the living fungal culture, called mycelium, grown onto a nutritious material or substrate. It provides the backbone to any mushroom growing operation. Think of it as the equivalent of seeds for a mushroom farm. Unlike seeds, though, mushroom spawn is already alive so care must be taken in storing and handling it.
Another big difference between spawn and seeds is that mushroom spawn relies on selecting particular genetics and cloning to achieve consistent production of a particular cultivar of mushroom. Farmers apply a similar method to growing apples by grafting wood instead of planting seeds. The grafts ensure that each plant will produce the same delicious variety of apples via the same set of genetics.
Seeds (and spores for that matter!) are a genetic grab-bag dependent on two individual sets of genetic material, while spawn is a single genetic culture that can be propagated indefinitely from the same 'master'. The 'master' cultures are kept on agar petri dishes in our laboratory.
What about spores?
It's true that mushrooms naturally grow from spores. However, those mushrooms are the success stories of an odds game played by each particular mushroom species. Each mushroom produces thousands of spores in a scatter shot approach to reproduction. With more spores floating in the wind, dispersed by rain, and moved about by insects and other creatures, the chances are better that they'll find the perfect environment to grow. The vast majority of spores dispersed will never germinate to become mushrooms. At North Spore we've selected for productive strains of edible fungi to maximize the success rate for people who use our spawn!
What are the different types of spawn?
We produce 100% of our spawn in our labs at our facility in Westbrook, Maine. Many of our cultures were isolated and grown from wild New England foraged mushrooms. To make spawn, we start by taking mushroom cultures from our culture bank and growing them out on our blend of sterilized organic millet and rye berries. That initial batch is called 'master spawn' and we use it to inoculate each bag of the next generation which includes three distinct types of spawn - and lots of mushroom species for each type! They are: grain spawn, sawdust spawn, and plug spawn. Each is distinguished by the substrate the mycelium is grown on and they all have particular uses, trade offs, and benefits.
Grain Spawn is grown on a blend of organic millet and wheat berries.
Plug Spawn is made with hardwood dowels about the diameter of a pencil and 1" long.
Sawdust Spawn is formulated with hardwood pellets and organic soy hulls
Considerations when choosing spawn
Some factors to consider in making a choice between spawn include:
+ Scale: How big or small is your inoculation project? Are you growing for home, your community, or commercially?
+ Resources: What resources are available to you for getting set up, including your time, equipment, and space?
+ Who will be inoculating: Are you flying solo and free to mosey, do you have a crew to zip through, or maybe you've got a few kids who want to help?
+ Investment: Are you looking to try out something new with low commitment, or are you all in for grabbing the gear and growing for years to come?
Grain spawn is most often used for commercial indoor operations, but has a few applications for outdoor growing, too! We recommend sticking to oyster species for these applications, since they're vigorous enough to compete with other microbes.
Though you won't be using grain spawn for growing on logs, it's a solid option for inoculating straw beds, bales, and less commonly wood chips. If you inoculate at a higher rate it could be successful for some container growing, as well. As a grain product, it's richer in nitrogen than wood based substrates. So, it can give your grow some added nutrition, especially useful for conditioning straw bales ahead of transplanting vegetables.
On the other hand, that nutrient density makes it more prone to contamination - other competitor fungi, microbes, and even larger creatures in outdoor spaces are eager to eat this rich food. That means in most cases, sterile technique and sterilized or pasteurized materials are encouraged for the best success.
A single 6 lb. bag can inoculate 100-130 pounds of pasteurized straw or a 16 square foot space. Details on making mushroom beds can be found in our Mushroom Bed Pamphlet
This is the type of spawn you'll see in our Outdoor Log Kits sold at garden centers, co-ops, and farmers' markets. They are locally produced wooden dowels that we've grown mushroom mycelium on and we pack them up in 100, 500, or 1,000 count bags for different project sizes.
Plug spawn is only used for inoculating logs in the traditional drill & fill method outlined in our log walkthrough. It's one of the best ways to get started growing mushrooms because the process is straightforward, a package is relatively inexpensive, and even kids can enjoy inoculating! One the log is drilled, all you need is a hammer and wax and you're good to grow.
What's more, as log kits, they're ideal for gifting. Opt for a voucher to be redeemed at your convenience.
While plug spawn excels for its ease of use and accessibility, it tends to be slower than sawdust spawn both in the time it takes to inoculate and the incubation period until fruiting.
Plug spawn is ideal for small to medium sized projects and a 100 count bag can inoculate 1-4 logs. Our log inoculation calculator can help you figure out exactly what numbers you need for your project.
For a full rundown on how to use plug spawn, see our Plug Spawn Pamphlet
Used much like plug spawn for log inoculations, though there are some distinct divergences. Sawdust spawn requires an inoculation tool to insert the spawn into the drilled holes. Combined with our angle grinder adapter and specially designed mushroom log drill bit, the inoculation process becomes a breeze to whizz through. The speed and efficiency gained from using sawdust spawn make it great for medium to large scale projects and it's the go-to method for commercial operations.
As you scale up, sawdust spawn is cheaper than plug spawn. It's also more reliable and colonizes faster. If you plan on inoculating logs for consecutive years, the investment in tools is offset by the lower cost of spawn.
If you're not attached to the traditional drill & fill style of growing on logs, sawdust spawn also offers a few more options. You can sandwich it between smaller sections of logs to grow in stacks via the totem method, use it to inoculate beds or make mycelial mulch, and even grow in a variety of types of containers! We love sawdust spawn for it's versatility.
One 5.5 lb. bag will inoculate a 4'x4' or 16 square foot space.
Some mushroom inoculation inspiration in 5 slides: