How Do Mushrooms Grow?

Neither plant nor animal, fungi are unique organisms. By learning more about their biology - how, where, and when do mushrooms grow - you'll gain insight into some common questions and be better equipped to start growing mushrooms yourself!

In the early years of North Spore, when we were still a fledgling mushroom business, countless days were spent standing behind folding plastic tables hawking colonized grain, sawdust, and wooden dowels - different types of mushroom spawn.

There, we met face to face with a public hardly aware of the diversity of fungi living all around them. In most cases, folks were skeptical, even mycophobic. What context did they have for fungi? Foraging and eating mushrooms are common in cultures across the world- look at these farms in Thailand! But most people we encountered hadn't been exposed to mushrooms beyond raw buttons in a salad bar or poisonous toadstools.

Recently, fungi have launched into the mainstream of American culture, moving beyond the unseen realm. From low-tech grows to the "wood-wide-web" to the medicinal potential of mushrooms, there's so much to learn about the kingdom fungi! To demystify these incredible organisms and get you started on your fungal discovery path, here's a primer on their biology.

What are fungi?

Fungi are everywhere. They pop up throughout our environments, appearing as mold on fruit, yeast in beer, and in our yards. Not quite a plant, and not quite an animal - they are a kingdom all their own.

It hasn't always been that way. Historically, naturalists classified fungi as a type of mysterious chlorophyll lacking plant sometimes called thallophytes. It wasn't until 1969 that scientists separated fungi into a kingdom separate from plants, based on evolutionary and biological observations. The advent of DNA sequencing more recently revealed that the fungal kingdom is more closely related to animals than plants! Mycology, as we know it today, is a very young science. Many of the terms mycologists still use today to describe fungi are vestiges of their residency in the Kingdom Plantae.

Fungi are eukaryotic organisms, meaning they are made up of cells whose DNA is contained in a nucleus bound by a membrane. So are plants and animals, but fungi diverge in some distinct ways. They do not photosynthesize like plants, so they cannot produce their own food. Instead, fungi are heterotrophs meaning they obtain nutrients from other organic material, often other organisms. Animals share this trait. However, animals ingest and then digest their food. Fungi, on the other hand, secrete digestive enzymes into their environment and then absorb the nutrients released.

The cell walls of fungi contain chitin, a strong but flexible compound also found in the exoskeletons of arthropods like beetles and crabs (and why cooking mushrooms is essential!). Though fungi lack a nervous system, their mycelial network is increasingly compared to one, acting as a biochemical conduit for interspecies communication between plants. Not only that, but they are also responsible for a significant amount of the world's decomposition, a critical component of nutrient cycling and carbon sequestration. Our terrestrial ecosystems rely on fungi's unique ability to break down lignan (a key ingredient in woody matter) and other complex organic compounds. Without fungi, our forests would never degrade, leaving heaps of woody debris piled sky-high.

The kingdom fungi is incredibly biodiverse, containing up to 12 million species, second in richness only to insects. They come in many forms: from microscopic yeasts who reproduce through a type of self-cloning called budding to the filamentous macrofungi we are more familiar with who reproduce by forming mushrooms.

While all flowering plants grow from seeds, mushrooms grow from either spores or tissue culture. Every mushroom releases thousands of spores into its environment, each carrying genetics unique to that spore. So, growing from spores is akin to planting a bunch of apple seeds - it can be unpredictable, and none will be identical to its "parent."

The mushrooms we are most familiar with, your classic cap and stem mushrooms, are members of the phylum Basidiomycota. All mushrooms in this group, including jelly fungi, puffballs, and porcini, produce their spores outside of club-like cells called basidia. Other, perhaps stranger looking mushrooms are in the phylum Ascomycota. Think morels, corals, and cups! Ascomycetes produce their spores internally, within sac-like cells called asci.

When one of these spores lands in the right environment, it'll germinate and send out a small filamentous thread called a hypha. These fungi grow from the tip of the hypha, a sort of bud of potential, extending forward in response to outside stimuli. While scientists don't totally understand this process, the dominant theory is that an organelle called the Spitzenkorper organizes and directs the growth patterns in pulses, like a microscopic architect.

The hyphae quickly begin branching, forming a dendritic network known as mycelium. The mycelium grows, gathering nutrients and water from its environment. When it encounters a compatible mycelium sprouted from another spore, it fuses and swaps nuclei forming a dikaryotic (containing two sets of nuclei) mycelium. Freshly united, this secondary mycelium grows through its environment until it runs out of food, space, or there's another signal like heavy rainfall or a change in temperature to start fruiting. Mycelium condenses into the tiniest stage of mushrooms - primordia. Mushroom growers sometimes call these pins. With the right conditions, the primordia become fully formed mushrooms complete with basidia or asci where they form spores and start the process anew.

How we can grow mushrooms is a little different. When we cultivate mushrooms, we mostly use tissue culture. At the beginning of this process, a section from a fresh mushroom is cut out and placed in sterilized media to grow, effectively cloning the mushroom. Fresh mushrooms are important - you want to use the living tissue of the mushrooms.

From there, the fungus begins sending out single-celled hyphae, which grow into mycelium. It's what you see when you get a bag of spawn. That white cob-webby stuff isn't mold, but mycelium on its growing material or substrate. That spawn is then used to inoculate new substrates. Growing from dried mushrooms is technically challenging, a topic for another post.

When do mushrooms grow?

Famous and funny mycologist David Arora titled a book All That the Rain Promises and More. Truly, a heavy rainfall is often a cue to go foraging for mushrooms. Fungi growing outside take cues from their environment to begin forming mushrooms. Changes in humidity, temperature, and moisture are major determining factors for when mushrooms grow, and each species of mushrooms has a particular preference. Just as tomatoes in Maine don't set fruit until June, mushrooms also have a sort of biological clock. As I write this in mid-summer, Chanterelles are just peeking out from leaf litter, orange beacons in the forest. After almost two months of drought and a few solid thunderstorms, the woods are alive again with fungi.

In the temperate Northeastern US, most edible mushrooms fruit between spring and fall (May-Oct.), dependent on good rainfall. On the opposite coast in the Pacific Northwest, mushroom season peaks between August and December, though Morels pop up in late spring and early summer.

Coast to coast, lots of medicinal mushrooms, including many hardier perennial polypores like Artist's Conk (Ganoderma applanatum), can be found year-round. Lots of ID guides specify when mushrooms grow in a particular region. We've compiled a list of recommended reading at the end of this article! One thing's for sure, across climates, mushrooms will follow rain.

This seasonality applies to cultivated mushrooms too! There are several different types of Oyster mushrooms commonly grown, each with some variance in growing conditions. Pink Oysters love the heat, only fruiting above 65 degrees F, whereas Snow Oysters like it a little chilly. Similarly, there are a variety of strains of Shiitakes that have been bred for different temperatures.

Mushrooms grown indoors lack the same environmental exposure as wild mushrooms or mushrooms in a garden. Typically grown in containers, these fungi concentrate their energy on colonizing their substrate until it's fully engulfed in mycelium. Once complete, the fungi runs out of food and space to keep growing. If we recall the fungal life cycle, these are both situations that trigger fruiting. Depending on the set-up, a grower may put their container into a specialized room or space with temperature and humidity controls to dial in for that specific species. On a smaller scale, martha tents and monotubs can help a home grower achieve the right conditions. Sometimes, the fungi can't wait and burst through their container. It's incredible how strong mycelium is!

Where do mushrooms grow?

Generally, mushrooms love to grow in moist, humid, shady areas, but they can also pop up in some pretty unexpected places. For a few years we found Morels growing out of cracks in the sidewalk near our Westbrook facility! If we know a little more about what type of food the fungi consume and what function it plays in its environment, we'll gain insight into where mushrooms grow.

Almost all of the fungi we can cultivate are saprophytic, meaning they're decomposers. Some specialize in digesting woody material - the only organism capable of this feat! Others break down nitrogen-rich substrates like manure. Mycorrhizal mushrooms are a bit more complex. These types of fungi partner with a plant host, exchanging scavenged nutrients in the soil for sugars. Many are very specific to their host, though a few are considered generalists.

Matsutake, a mushroom highly coveted in Japan and a major topic of the book The Mushroom Hunter, is rare to find on the East Coast. Preferring a specific type of clay soil common to colder climates, and a select few conifers (eastern hemlock, red pine, jack pine), this mushroom is a specialist. Finding mycorrhizal fungi can be more challenging, requiring some skill with plant identification and mushroom ID, though you can certainly stumble upon honey pots! Personally, we find more joy in finding just the right ecology for a particular mushroom, for all the variables to fall in line at the right time.

You can also learn so much by walking in the woods with folks who've been hunting mushrooms for a while. There are tons of local mycological clubs that you can join on forays. Here's a good resource to check if there are any in your area.

If you're considering growing indoors and wondering where to grow, there are many options. Mushrooms can easily be incorporated into your garden, your porch, or woodlot. A spot with dappled shade is ideal, though some species, like Wine Cap, tolerate a bit more sun. Inside, Spray & Grow Kits can live on your table, acting as a centerpiece while the mushrooms unfurl. A friend of mine kept hers on a shelf in her bathroom - the high humidity environment helped produce huge clusters of mushrooms! Closets and basements may be a natural choice, being dark and maybe even damp. Anywhere outside of direct sun can work, especially growing in containers like monotubs and martha tents.

How can I grow mushrooms?

There are so many different ways to cultivate edible, medicinal, or even psychedelic mushrooms (if it's legal in your area!) Where you choose to start may depend on your space, time, and resources.

If you're just dipping your toes into growing mushrooms, want to get a feel for the process before diving into a more intensive grow, or looking to grow some mushrooms quickly, try a Spray & Grow Kit. Just cut open the box, mist regularly, and you'll have mushrooms fruiting on your kitchen counter in no time! These kits are an excellent activity for your household and make for some interesting home decor.

Are you looking for something a bit more hands-on? Try growing in a monotub or martha tent. These low-tech cultivation techniques use a fruiting chamber, allowing you to adjust temperature and humidity specifically for the mushrooms you're producing. You can also grow mushrooms directly in a bag. Mitigate contamination when working indoors with a still air box. Larger indoor grows require some more infrastructure and a good grasp of aseptic technique, so we recommend reading up before getting your hands gloved.

Growing outside can be incredibly fruitful, too! If you have any wooded land, lots of perennial plant cover, or evergreen shrubs or trees, you most likely have a suitable environment for outdoor mushroom beds or logs.

Mushrooms can also be easily incorporated into your garden, benefitting the soil and surrounding plants. You can tuck them into mulch in vegetable beds or paths, inoculate containers or bales, or even bury blocks. Any way you choose to grow, you want to make sure the fungi stay moist, especially if there's a drought, and that they don't receive too much direct

Starting with species that are sure to grow, like Blue Oyster (Pleurotus spp.), Wine Cap (Stropharia rugosoannulata), and Shiitake (Lentinula edodes) is the best way to cut your teeth and keep your mushroom growing morale high.

As you learn more, feel free to experiment, and don't hesitate to us if you've got questions or to share your mycological journey!

How Do Mushrooms Grow?

What are fungi?