How to Grow Your Own Mushrooms

Mushrooms, the fruit of certain types of fungus, will provide a steady supply of fresh, nutritious ingredients, and they're gaining popularity.

As the weather turns colder and you cook up the last of your fall harvest, you may want to consider what you can grow indoors to supplement your winter menu with a steady supply of fresh ingredients. Mushrooms are an increasingly popular option.

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Mushroom basics

It is estimated that there are at least 10,000 species of mushrooms in North America. Of those, about 250 are known to be edible. An equal number are known to be poisonous.

Mushrooms are the fruit of certain types of fungus. Not all fungi produce mushrooms. For those that do, the mushrooms’ primary function is producing reproductive spores. The spores germinate into masses called mycelium. Just like plants, fungi need food and moisture, and most need sunlight to grow. When conditions are just right, the mycelium sends out “pins.” After several days — up to a week, depending on the variety — the pins develop into mushrooms.

Some varieties of mushrooms are easier to grow than others because they are less picky about temperature and humidity. The North American Mycological Association (NAMA) recommends novice growers start with oyster mushrooms because they are the easiest to grow.

There are many techniques for growing mushrooms. NAMA recommends starting out with a kit, which will provide you with everything you need and detailed instructions. There are many resources online and on the NAMA website for ordering kits, as well as supplies you need.

Aside from kits, there are many techniques for home-cultivation of mushrooms. In the spring and summer, you can grow them outdoors in your garden. To bring the process indoors you may have to get a little creative, but growing mushrooms is a great project to do with your kids. The rewards are worth the effort.

What you need to grow your own

There are many types of mushrooms to choose from, and nearly as many growing methods. Below are some basic steps for starting your own indoor mushroom patch.

Decide on a mushroom species. What kind of mushroom do you want to grow? In addition to oyster mushrooms, commonly cultivated species include shiitake, crimini, portobello, lion’s mane, and enoki. Once you’ve decided, order the spawn (the mushroom equivalent to seeds) from a mushroom supplier. Again, many resources are on the NAMA website, or simply do an internet search for “mushroom spawn.”

Growing material. What kind of material (called substrate) do you want to grow your mushrooms on? What you use may be dictated by the mushroom species you’ve chosen. Some common substrates are straw, sawdust, woodchips, logs, even toilet paper rolls. If you choose logs, woodchips, or sawdust, make sure the wood is from a hardwood variety, not a pine or evergreen. If you plan on growing mushrooms regularly, it’s good to choose a substrate that is readily available and within your budget.

Growing container. You can grow mushrooms in a variety of containers, from a simple plastic bag, to a cardboard box, an aluminum roasting pan, half a milk carton lined with a plastic bag, or a laundry basket, convenient for its pre-made holes.

Let’s assume you’re going to grow oyster mushrooms using straw for your substrate and a laundry basket for your growing container. If this size seems too ambitious, start with the milk container and adjust the process accordingly.

The first step is to pasteurize your substrate. This serves two purposes:

1. It kills any micro-organisms, molds, or bugs that may compete with or contaminate the mycelia.
2. It introduces moisture into your substrate, which the mycelia need to grow.

Chop the straw into smaller pieces. This increases the surface area on which the mycelia grow, and makes it easier to handle.

To get started, gather the following items:

• Clean growing container
• Substrate
• Spawn
• Large pot
• Thermometer
• A clean, waterproof container large enough to hold however much substrate you need to fill your container (a cooler works well)
• A screen or large rack
• A tarp or large piece of cardboard
• Agricultural lime (calcium carbonate)
• Agricultural gypsum (calcium sulfate)
• Plastic large enough to cover your growing container

Fill the pot with water and heat it to 180 degrees. While you’re waiting, fill your container with your substrate a little at a time, pushing it down as you go. Sprinkle 1/4 cup of lime and 1/8 cup of the gypsum (available at your local garden center or hardware store) over the straw and mix it in. Pour the water over the straw until it’s just covered, cover the container, and let it sit for 1 ½ hours. (There are also several methods for cold pasteurization.)

Arrange the screen or rack over the cardboard or tarp by placing it on “legs” — anything that will hold it above the ground and allow air to circulate to cool and dry the straw. Drain the water from the container and remove some of the straw, spreading it out to cool. Hot substrate will damage your spawn.

When the straw is cool to the touch and squeezing a handful yields just a couple drops of water, place a 2-inch-thick layer in the bottom of your container. Arrange a layer of spawn on top of the straw (inoculation). Cover with more straw and another layer of spawn, repeating the process until your container is full. Cover your container with plastic (a trash bag will work) to create humidity.

Spawn run

Place the container in a dark room with a constant temperature of about 75 degrees. After about a week you should see white mycelium starting to cover the straw. This is called the spawn run. Check your container again after another week. Once the mycelium has completely covered the straw, which may take up to three weeks, you are ready for the next step.

Primordia

Your mycelium now needs a little air and light and continued humidity. Move your container into a room where it will receive indirect light. Several times a day lift the plastic off the container or make several cross cuts in the plastic to promote air circulation. With a spray bottle, mist the container once a day. If you used a plastic bag for your container, make several cross cuts to allow the mushrooms out — and air and mist in. After about a week your substrate should be covered with primordia, which look like tiny pins.

Enjoy the fruits of you labor

Once pins appear, you are at the fruiting stage. Continue to mist and expose your culture to fresh air and light. It may take as long as a week for the pins to turn into full-sized mushrooms, but it can happen quickly so keep an eye on them. Pick your mushrooms before the outer edges turn up, when they’re past their prime.

Mushrooms have many health benefits

Mushrooms, both culinary and medicinal, have many health benefits. Understanding their medicinal potential is an active area of research. When exposed to light, mushrooms are the only non-animal food source of vitamin D. They also provide vitamin B-12, selenium, and a variety of antioxidants that protect against cancer and heart disease, and help regulate blood sugar. They improve gut health, immune function, and possibly oral health. Substituting mushrooms for meat can also be an effective and satisfying way to lose weight and keep it off.

Similar to tomatoes, the nutritional benefits of mushrooms are most available when they are cooked. With a little planning and effort, you could soon be harvesting the rewards of this versatile fungi.

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