Testing Out Mushroom Grow Kits: Harvest in 14 Days!

Mushroom grow kits are a lot of fun because these immune–boosting treats grow very fast (as quickly as two weeks!). We’ll show you how it works by demonstrating two oyster mushroom kits, which are great for beginners because they grow SO fast—in as little as two weeks from preparation to picking.

About Mushroom Grow Kits

Most people often start using store-bought “ready-to-fruit” kits with complete instructions for beginners. You can grow the mushrooms in 14 days and harvest your shrooms at the peak of perfection. 

Mushrooms are powerhouses of goodness and great at fighting off diseases. Plus, they’re delicious in any meal—even breakfast with eggs; in fact, they’re the breakfast of champignons. (Get it?)

Please buy mushroom spores and kits from reputable sources only. A few U.S. suppliers that have good reputations are: 

1. North Spore
2. Forest Origins
3. 2FunGuys

How Mushroom Kits Work

We’ll demonstrate two easy-to-grow methods for Oyster Mushrooms because this type grows so quickly. You can watch the video and follow the instructions below!

1. Oyster Mushroom Kit (using straw)

For this kit, we’re using a large pot of around 2.5 gallons, or you could use two pots of half this volume each. The growing medium is straw, pressed into pellets, and ready to be rehydrated.

• Prepare the pot: Clean and sterilize the pot with a dilute household bleach solution. Cover the drainage holes with a circle of cut-to-size cardboard pushed to the bottom of the pot. Using scissors, cut holes into the sides—three holes around a half-inch in diameter. Space them evenly around the circumference and also evenly from bottom to top.
• Prepare the straw and grain: Break up the grain containing the mushrooms’ spawn. Empty the straw pellets into the pot, then add the broken-up grain kernels to the straw pellets and mix well to distribute evenly. Make sure to use very clean hands so you don’t introduce unwanted germs! It’s best to do this outside to make a mess.
• Water: Measure about a gallon of water and slowly trickle-pour half over the spawn mix. Allow the water to become fully absorbed—around half an hour—then add the rest slowly. Once the straw pellets have fully rehydrated to fill the pot, push back the straw from your three holes to leave a cavity. This will keep this area moist and protected so the mushrooms can properly develop.
• Make the lid: The lid will stop everything from drying out. A simple way to make one is to cut out a round of stiff cardboard to fit it, then wrap it in clear food or plastic wrap.

Now it’s prepared, we need to offer warm conditions for the mycelium—or mushroom ‘roots’—to grow. Room temperature is ideal, but keep the pot away from direct sources of heat. If it’s the summer, you could keep the pot outdoors, somewhere sheltered and out of direct sunlight.

To keep things going, simply mist-spray the holes a couple of times a day. This will prevent the straw from getting too dry and offer the moist environment that mushrooms need.

And here it is after two weeks, with the straw now totally white with mycelium. At this stage, our kit’s ready to produce its first flush of mushrooms!

Continue misting the holes twice daily, and within a week or two, you should notice small clusters of primordia—the beginnings of the fruiting bodies—the mushrooms—that we’ll be picking. At this stage, misting becomes even more important, as you really don’t want these to dry out. They’ll soon swell into full-sized mushrooms, and this shouldn’t take more than about a week after spotting the primordia.

The best time to harvest oyster mushrooms is before the caps have fully flattened out, when they dump lots of spores everywhere! Twist-free the whole cluster at once—the mushrooms will be different sizes, and that’s fine—and trim any stump out with a sharp knife right back to fresh straw. Continue misting, and new mushrooms will sprout from the harvested hole eventually. They should keep cropping every few weeks for up to around ten weeks.

2. Coffee Grounds Kit (using grounds and straw)

I hate waste, and your daily cup of Joe creates quite a bit of it in the form of these coffee grounds. Try a kit that uses coffee grounds mixed with a little straw to create the ideal growing medium for our mushrooms. Let’s get it started.

Cut open the front of the box and cut out a cross into the front of the bag. Soak the bag overnight, let it drain off, and pop it back into the box. Mist the front of the box that’s cut open with water twice a day. Keep the kit on a windowsill or work surface out of direct sunlight and, again, avoid direct sources of heat. 

And here you can see the primordia—about seven days after opening your kit and starting it off. These grow very quickly—doubling in size almost every day! Again, harvest the mushrooms when the caps have just started to open out but haven’t yet flattened out. Flattened-out mushrooms don’t store for quite as long and aren’t quite as firm and flavorsome. To harvest, simply twist and pull them away with your hands like this.

Growing Additional Harvests

You can also grow a follow-on flush of mushrooms. Usually, you can grow 2 to 3 more harvests.

To do this, allow the kit to rest for two days following harvest, then just soak the block in water just as you did when you started it off. Weigh it down if necessary. Lift it out, allow the excess moisture to drain off, then pop it back into the box and mist regularly, as before. 

The second crop should follow within a couple of weeks or so. And once you’ve had that harvest, repeat the process once more!

Interested in growing mushrooms without a kit? See our “How to Grow Mushrooms” plant page!