Can You Propagate Store-Bought Mushrooms?

Wondering if you can re-grow mushrooms you purchased at the grocery store? You absolutely can. They can be propagated from store-bought with a bit of research, time, and luck.

If you buy mushrooms frequently, whether you’re getting them at the store or from the farmers market, it’s no wonder why you may want to cultivate more of your own. Perhaps one of the only downsides of a mushroom-packed diet is that they tend to be expensive, especially if you eat them often. They also expire fairly quickly, possibly requiring you to purchase them more often.

Fortunately, they can be cloned at home, mostly with materials you probably already have lying around. Buying mushrooms at the farmers market may be pricey, but growing them at home certainly is not. So why not give it a try?

The Short Answer

Good news: you can propagate store-bought mushrooms at home, using materials that are affordable and that you may already have. Oyster mushrooms are one of the easiest types to grow, and you can usually find them at the store. Because the process is easy and inexpensive, it’s worth a shot.

The Long Answer

Propagating store-bought mushrooms at home is not only possible but also is pretty straightforward. We’ll cover the basics of how to propagate, list the materials needed to encourage the process at home, walk you through the steps of how to make it happen, and even tell you how to preserve your home-grown harvest.

How Do They Grow?

But first, some crucial background information. In the wild, when you see mushrooms, you are seeing the fruiting bodies of a fungus. The mycelium of the fungus, which is essentially a network of fungal thread below ground, sends up these fruiting bodies to release spores.

The fruiting bodies release spores through various mechanisms, and in the right conditions, the spores form new mycelium. This is how they reproduce. A single spore is all it takes to make mycelium.

Mycelium in Stems

While spores can be purchased, if you have mushrooms in hand, you actually already have access to mycelium. You are already one step ahead in the process. This is the tissue you hope to grow when cloning mushrooms from the local grocery.

Mycelium should exist in the stems, and sometimes you can even see the mycelium at the bottom. This will look somewhat like a stringy web where the base of the stem meets the substrate in which it was cultivated.

So, which species should you try? Oysters are a great place to start. They are widely cultivated, because oyster mushrooms grow easily. You should be able to find them at most grocery stores, and most people are familiar with oysters.

Shoppers may also be familiar with the names “button,” “cremini,” and “portobello.” These are actually all the same species, Agaricus bisporus, harvested and sold at different life stages. These shrooms are possible to propagate at home as well.

Though we’ll be discussing oysters going forward, don’t count out this common produce aisle species, especially if you find some that have visible mycelium on the bottom of the stems.

What You’ll Need

To propagate your grocery oysters, there are a few things you’ll need. First and foremost, grab your favorite fungi. If you happen to see a package of oysters with a chunk of mycelium attached, even better.

Next, you’ll need substrate. This is the material in which the oysters will grow. Straw, coffee grounds, cardboard, and even hamster shavings are all commonly used for at-home mushroom growing. What matters most is that the substrate contains cellulose-based material, and it needs to be sanitized, which will be one of your first steps.

You will also need some sort of container, in which you’ll put your clean, prepared substrate, and your oyster stems. New oysters will grow in the container you choose. There are a lot of options, including a plastic tub, a cardboard box, or a plastic bag.

Finally, give some advanced thought as to where you will put your container while the mycelium is colonizing and expanding. Ideally, it should be placed somewhere dark and at fairly consistent room temperature, without any blowing air. 

How to Re-Grow from Store-Bought

Once you gather what you need, you will be ready to get started. The first step is to sterilize your substrate. There are multiple ways to do so, and most involve heating the material to a degree that kills any organisms that may compete with your mycelium. 

A tried and true method is to use your oven. You can place the substrate on a baking sheet, cover it with aluminum foil, and cook it at 170°F (77°C) for about three hours. You can also sterilize substrate in a pressure cooker, whether you cover it with water and boil it or steam it in a bag. 

If your sterilization method involves water, wait for the substrate to cool, and then drain. Now you have clean substrate. Your next step will be layering the moist material in your container with the cut up stem pieces.

Dampen the substrate if it’s dry, and add a layer to the bottom of your container. Now, you want to gather the stems. Wash your hands thoroughly, or wear gloves when preparing, and use a clean knife.

Cut up pieces of stem that are no smaller than ¼ inch. You can disregard (or eat!) the caps. Spread out your stem pieces on the substrate, and then cover them with another damp layer.

As the mycelium is growing, you cannot let the substrate dry out. An easy way to prevent this from happening is to cover your container with some plastic wrap or a plastic bag. Poke some holes in the plastic, encouraging just a little bit of airflow. 

Place your prepared container in a dark spot away from any drafts, like in a closet, up on a shelf, or under the sink. Your next step is to remain patient while the mycelium colonizes the substrate. If the substrate begins to dry, you can mist it with fresh water. 

In a few weeks, you should see the mushrooms starting to form. At first, you will see primordia, or pinning, which is when a white mass forms. You will see this mass begin to take the shape of small, initial structures, called pins.

At this stage, your harvest is starting to come together. Adjust your plastic covering so that it just barely covers the whole container in a tent shape, leaving room for the oysters to flourish. Make sure that airflow is possible.

Over the next couple of weeks, you’ll see the fungi grow larger, and then they will be ready to harvest. Use a clean knife to slice them off when they’re ready. Since mushrooms have a short life cycle and expire quickly, you’ll want to harvest and eat them frequently.

How to Store

If you aren’t able to eat your harvest right away, place them in a paper bag in your fridge, and they’ll be good for a few days. Ideally, leave them attached to the fruiting substrate until they are at the perfect size, harvest, and eat right away.

What shape and size is ideal for harvest? It depends on the species, but for oysters, you will want to pluck them just as their caps uncurl, regardless of size. They should be at least about two inches wide at this point, but sometimes smaller specimens will form. Though this is a good rule of thumb, it’s okay if you harvest slightly early or late.

If you aren’t going to be able to use a lot of the mushrooms in a narrow window of time—perhaps you are leaving town for a few weeks—you can harvest as many as possible and preserve them. Because they decay rapidly, you can dehydrate using a dehydrator or freeze them.

Place dehydrated mushrooms in an airtight container and keep in a dark spot. They should be good to use for about a year. If you’d rather keep them in the freezer, blanche the them and then promptly freeze them in a single layer, where they should also be good for about a year.

Grow More

If you dig the idea of growing mushrooms at home, propagating them from the market is not the only way. You can grow shiitakes, lion’s mane, and many other species at home via multiple methods.

Inoculating straw beds in your garden with grain spawn, following the instructions on a fruiting block kit, and even using spawn plugs to grow mushrooms from logs are all options. Even if you’re a total beginner, there’s a trouble-free alternative: spray-and-grow blocks that are nearly fool-proof.

There’s no need to limit yourself to common produce section species, either. You can attempt to cultivate as described above with many types, including those that you’ve foraged, though the results will vary. If there’s a specific mushroom you want, research the best way to grow it. There’s a good chance you can do so at home.