Grow Mushrooms On Compost For A Flavorful Feast

Want to start growing flavorful fungi but intimidated by the process? Don't be—you probably already have what you need to grow mushrooms on compost.

by Rachael Dupree
PHOTO: Field & Forest Products

There are many reasons people get into mushroom growing.

For some, it offers a delicious array of alternatives to—let’s face it—bland grocery-store mushrooms. For others, it’s an exciting new foray into growing your own food.

But if you think that mushrooms can only be grown on freshly cut logs tucked away in a shaded corner of your farm, think again. Mushrooms are skilled decomposers, so when looking for new ways to grow them, look no farther than your compost pile.

Rot Away

To understand growing mushrooms on compost, you first have to understand the role of mushrooms in nature, says Mary Kozak of mushroom spawn supplier Field and Forest Products.

Fungi are decomposers, and each species of mushroom “eats” different materials that vary in stages of decomposition.

High on the rot chain are primary decomposers—mushrooms such as shiitakes and oysters—which get their nutrition from newly dead or just-cut trees. A little further down are litter decomposers, such as wine cap stropharia. These subsist on leaf litter and wood chips.

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Down from that are mushrooms such as blewits that thrive on garden or yard refuse material. And at the bottom, you have the compost mushrooms that can be grown on finished compost.

The type of mushrooms you want to grow in conjunction with your compost will depend on composting and culinary goals. If you are looking to break down raw materials, select a mushroom a little higher on the rot chain. But compost mushrooms can be “planted” in a bed of finished compost much like you would other garden vegetables.

Bear in mind that cultivation can get more complex farther down the rot chain.

“The most successful and easiest way [to grow mushrooms] is on logs or straw outdoors because nature has already done the semi-selecting of the substrate,” Kozak says.

However, if you’re looking to try a new mushroom-growing method or explore the broad range of flavors that mushrooms can provide, it’s worth experimenting with species farther down the decomposition chain.

Starting at Rot Bottom

When aiming to grow mushrooms on compost, you’re looking for a category of mushrooms called secondary decomposers. According to mushroom-growing great Paul Stamets in his book Growing Gourmet and Medicinal Mushrooms, these move in after the fungi higher up in the rot chain have done their jobs.

You can find the best-known of the compost-grown mushrooms in every supermarket across the country: the white button, crimini or portobello (Agaricus bisporus). (Yes, these are all the same species of mushroom. Think twice before you spend a little extra on the brown variety.)

The mushroom at the grocery was likely grown indoors in a giant warehouse. But in nature, it can be found on well-manured grounds, rich soils, meadows, grasslands, forest edges and roadsides.

To best replicate this environment on your own farm, and thus explore flavors that the grocery store can’t compete with, Stamets recommends mixing clumps of grain spawn into compost and forming into outdoor rows. However, there’s one caveat to success. You need mushroom-growing experience.

“In order to have a reasonable crop, you have to have compost that has ability to select against [competitor fungi] that also like it, and then provide a healthy growing environment,” Kozak says.

This mushroom is simply not easy to grow.

But that’s OK. If you’re a beginning mushroom grower or looking to carve out a niche at your local farmers’ market, you still have compost-growing options. Kozak whole-heartedly recommends feasting your eyes (and stomach) upon portobello’s cousin, the almond agaricus (Agaricus subrufescens).

A Button of a Different Flavor

The thing that makes the almond agaricus shine is its flavor. That’s exactly why 2 Angels Mushroom Farm, a sustainable mushroom-cultivation operation in Chattanooga, Tennessee, added it to its menu of farm-raised and wild-crafted mushrooms.

The first fruiting offers big, bulky mushrooms. They have a distinct almond aroma and flavor that pair well with chicken or cornmeal. As a bonus, someone with minimal mushroom-growing experience can easily tackle it.

Unlike Agaricus bisporus, almond agaricus grows well in a broad range of composts. This means it will thrive in the diverse range of homespun composts. And while it’s a warm-weather lover, it’s hearty enough to survive as temperatures dip toward freezing.

Plant this species after the last frost of winter—in May or June in northern climates or earlier in southern climates. Simply bury chunks of spawn in a 5-inch layer of compost, then mulch and water. You’re likely to get three to five flushes throughout the season.

Find Your Fungus Path

With these growing instructions in mind, your foray into growing the almond agaricus can take several different forms.

Angela Miller, who owns 2 Angels Mushroom Farm with her husband, takes two different approaches—one grown in a bed placed around a chestnut tree and one intercropped with their cucumbers. Both yield fantastic results.

Growing in the shade of a tree helps keep moisture of the bed in tact. But growing the mushrooms as a companion crop has mutual benefits for the cucumbers.

“They break down large organic compounds, which are too big for plant roots to absorb, into a simple form that is bioavailable to the roots of nearby plants,” Miller says. “The action of fungi improves our soil while feeding our plants. That’s a win-win for any gardener. Our cucumber production doubles when paired with this mushroom.”

mushrooms on compost by tomatoes
Field & Forest Products

Kozak has also planted the almond agaricus under greenhouse tomatoes. This can extend the harvest season of this flavorful mushroom. Seeing the scattering of pearls and white round balls pop up at the base of your crop—the first sign of mushrooms—is very exciting, she says, even for the seasoned mushroom grower.

Get Compost Ready

The almond agaricus is pretty laid-back when it comes to it’s compost requirements. But there are things you can do to make sure you get the best harvest possible.

First, as a safety measure, Kozak recommends shying away from animal-based manures unless you are certain that your compost has reached a temperature that rids it of pathogens. That being said, Miller says they’ve found the most success with well-aged rabbit manure. The key term there, however, being “well-aged.”

You also want to create a fairly moist growing medium, Kozak says. Mushrooms obviously love a damp environment. But too much moisture creates a structure that doesn’t allow for air flow.

“The moisture content should be around 65 to 72 percent,” Kozak says. “Squeeze a handful as hard as you can and you should get one to two drops.”

If you find your compost is too dry, introduce hydration gradually. Spray and turn the pile over a period of time.

As long as you have properly heated your compost heap and have maintained proper moisture, your home compost should do the trick. Are you less confident in your compost-making abilities? You can always purchase compost for your mushroom beds from a reliable source.

A Chain Reaction

As you move farther up the rot chain, there are more mushrooms to consider growing in conjunction with your compost pile. They, of course, come in a broad range of flavors and growing ease. But here are a few to consider.

Wine Cap Stropharia (Stropharia Rugosoannulata)

Aka garden giant or king stropharia, this mushroom has a crisp texture and slightly nutty flavor, and it makes a great garden companion crop. For the beginning mushroom grower who wants to grow outdoors, it’s a shoe-in.

As a litter decomposer, wine cap grows well on wood chips or sawdust as a perennial or straw as an annual. While the mushroom can be grown in a bed all its own, you can also scatter the substrates among perennial beds or under fruit trees to increase soil fertility and suppress weeds.

When using wood chips or sawdust, clear the area of weeds and sod, spread the material a few inches deep, and then gently rake in the sawdust spawn. For straw, select a bale of oat or wheat straw (not hay, as it’s too rich a substrate), and soak in water for several days.

Pack the hydrated straw into the bed about an inch deep and layer with sawdust spawn, repeating for a few layers. Cover with plastic mulch to retain the moisture for a few weeks, and then remove to let the fruiting begin.

A study recently performed by the mycologists at Field and Forest Products found that plants intercropped with the wine caps grew with increased vigor. If you were to grow the mushrooms in a separate bed, resulting material “eaten” by the mushrooms is a great form of organic matter that can be used in garden beds as a soil amendment, as well.

Wood Blewit (Clitocybe Nuda)

If you’re looking for a beautiful mushroom, add some color to your compost pile or garden row with wood blewit’s varying shades of pink, blue and lavender.

It’s a dense mushroom with an earthy flavor. While in its natural environment, you’ll spy wood blewit growing among the forests’ decaying leaf litter. This mushroom’s preference for slightly decayed organic matter makes it a great candidate for growing on garden refuse—both in a compost pile or straight in the garden.

Because of the longer wait period for these mushrooms, it’s best to put them in a semi-permanent location. Harvest them when they are fairly dry to help preserve the shelf life, which can be up to two weeks when picked in optimal conditions.

If you plant in a semi-wild location, be aware of colorful impostors that could potentially pop up in your mushroom bed.

Cortinarius violaceus grows in similar conditions to the wood blewit, though it doesn’t have as distinct a smell and feels different. If you suspect this lookalike is trying to move its way in, take a spore print. The Cortinarius violaceus print is brown while the wood blewit print is white.

Shaggy Mane (Coprinus comatus)

Also known as the shaggy inky cap, this mushroom is more suited to a well-attentive grower, but with its crisp, asparagus-like flavor, it offers another diverse option for your mushroom repertoire.

You can grow this mushroom in a home compost pile or manure-enriched soils. The shaggy mane appears to thrive in the ammonia environment of active compost piles, though they won’t survive when the pile reaches its hottest point.

Harvest the mushrooms at a young age—early in the morning—because they quickly “melt” from a process called autodigestion. For this reason, they also don’t have a shelf-life—you have to eat them immediately. While this makes it impractical for the market grower, it can be a fun project for a hobbyist.

You probably already know your garden is full of interesting science-experiment potential, but introduce mushrooms to your beds and compost pile that are lower down on the rot chain, and the wonders of nature truly come to life.


Sidebar: Wood Blewit Production

Unlike the almond agaricus and wine cap, the wood blewit requires a somewhat more patient grower. Field and Forest recommends two methods for production:

Fall — Easy Growing

The easiest method for planting wood blewit is to start in the fall.

As you’re cleaning up garden waste, layer the spent plants with chunks of spawn, adding in a layer of finished compost every third layer of so to hold in moisture. You call also bury the spawn in a composted hay bale or large layer of grass clippings that has been well-hydrated, let it sit out overwinter, then spread out the material into the garden as a thick layer of mulch in the spring.

While both of these methods are low intensity, what you gain in ease, you pay for in time. Don’t expect to see your first fruiting for at least a year.

Spring — Maximum Results

For a quicker, more plentiful harvest, grow your wood blewits in their own bed.

Layer compost materials with spawn at least 8 to 10 inches deep. Spent oyster mushroom straw works great as a substrate, as does composted straw, composted grass and leaves, and vegetable matter. Then mulch the bed, and keep it well-hydrated.

This story originally appeared in the November/December 2019 issue of Hobby Farms magazine.

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