Growing your own mushrooms at home doesn’t require a fancy setup or green thumb—all you need is a cardboard box, some basic supplies, and a little patience. This method is affordable, eco-friendly (it reuses cardboard!), and perfect for beginners in the U.S. who want to enjoy fresh, homegrown mushrooms without a lot of hassle. Let’s dive into the step-by-step process, plus pro tips to ensure your fungi thrive.
What You’ll Need (Easy to Find in U.S. Stores)
Before you start, gather these supplies. Most are available at grocery stores, garden centers, or online retailers like Amazon or Lowe’s:
-
Cardboard box: A medium-sized box (12x18x6 inches works great) made of plain cardboard—avoid boxes with wax coatings or colored ink (these can be toxic to mushrooms).
-
Mushroom spawn: Choose a beginner-friendly variety! Oyster mushrooms are the best pick—they grow quickly and tolerate home conditions well. Look for “grain spawn” or “sawdust spawn” (not just spores, which are harder to grow).
-
Cardboard strips or sheets: Tear up extra plain cardboard to layer with spawn.
-
Water: Distilled or tap water (let tap water sit overnight to dechlorinate if possible).
-
Spray bottle: For misting (any basic spray bottle from the dollar store works).
-
Plastic bag or plastic wrap: To create a humid environment.
-
Dark, cool spot: A closet, basement, or under the sink (ideal temperature: 65–75°F/18–24°C).
-
Sharp knife or scissors: For cutting the box later.
Step-by-Step Guide to Growing Mushrooms in a Cardboard Box
Step 1: Prepare the Cardboard
First, you need to soften the cardboard so the mushroom mycelium (the “roots” of the mushroom) can easily grow through it. Tear the extra cardboard into strips or small sheets (about 2–3 inches wide). Soak them in water for 10–15 minutes until they’re fully saturated. Squeeze out excess water—they should be damp but not dripping (if water drips when you wring them, squeeze harder).
Line the bottom of your cardboard box with a 1-inch layer of the damp cardboard strips. This creates a base for the spawn.
Step 2: Layer Spawn and Cardboard
This is where the magic starts! Sprinkle a thin layer (about ¼ inch) of mushroom spawn over the base layer of damp cardboard. Make sure the spawn is evenly distributed—this helps the mycelium spread uniformly.
Add another layer of damp cardboard on top of the spawn, pressing down gently to ensure good contact between the spawn and cardboard. Repeat this process: cardboard → spawn → cardboard, until you fill the box about ¾ full. Finish with a top layer of damp cardboard (no spawn on top).
Pro Tip: Don’t pack the layers too tightly—mycelium needs a little air to breathe. Press just enough to keep the layers from shifting.
Step 3: Create a Humid Environment
Mushrooms love humidity—they need 80–90% humidity to grow. Cover the top of the box tightly with plastic wrap or place the box inside a large plastic bag. Poke 5–6 small holes in the plastic (use a toothpick or fork) to allow a little fresh air in—this prevents mold growth.
Step 4: Let the Mycelium Grow (Incubation Period)
Now, place the box in your dark, cool spot (65–75°F). This is the “incubation phase,” where the mycelium will spread through the cardboard. You don’t need to mist or check it often—just leave it undisturbed for 7–14 days.
After about a week, check for white, thread-like growth on the cardboard—that’s the mycelium! Once the mycelium has spread through most of the cardboard (it will look like the box is filled with white fuzz), you’re ready to move to the next step.![]()
Step 5: Trigger Mushroom Growth (Fruiting Phase)
Now it’s time to get those mushrooms to pop! First, remove the plastic wrap. Use a sharp knife to cut 2–3 slits in the side of the box (each about 2 inches long and 1 inch wide) where the mycelium is most visible—this gives the mushrooms a place to grow out.
Move the box to a spot with indirect light (a windowsill with a sheer curtain works great—avoid direct sunlight, which can dry out the mushrooms). Now you need to maintain humidity:
-
Mist the cardboard and the inside of the box 2–3 times a day. The cardboard should stay damp, but not soaking wet.
-
You can cover the top of the box loosely with plastic wrap (leave a 1-inch gap on one side) to trap humidity, but make sure there’s some air flow.
Step 6: Harvest Your Mushrooms
In 5–7 days, you’ll see small mushroom “pins” (baby mushrooms) growing from the slits. They’ll grow quickly—usually doubling in size every day! Harvest them when the caps are fully open but before the gills underneath start to turn dark (for oyster mushrooms, this is when the caps are flat or slightly curved).
To harvest, gently twist the mushrooms at the base or cut them with a sharp knife. Don’t pull them—this can damage the mycelium, which might grow more mushrooms later!
Pro Tips for Success (U.S. Climate Considerations)
-
Choose the right spawn: Oyster mushrooms are perfect for beginners, but you can also try shiitake or lion’s mane if you want to experiment. Buy spawn from reputable U.S. suppliers like Field & Forest Products or Mushroom Mountain.
-
Control temperature: If your home is too warm (over 75°F), place the box in the basement or near an air conditioner. If it’s too cold (under 65°F), put it near a warm vent (but not directly on it).
-
Avoid mold: Mold is the biggest enemy! If you see green, black, or blue fuzz, remove that section of cardboard immediately. Make sure there’s air flow (don’t seal the box completely) and don’t over-mist.
-
Second harvest: After harvesting the first crop, mist the box regularly for another 1–2 weeks. You might get a second smaller crop of mushrooms!
Final Thoughts
Growing mushrooms in a cardboard box is a fun, affordable way to enjoy fresh produce at home—perfect for apartment dwellers, busy parents, or anyone new to gardening. With just a few supplies and some basic care, you’ll be eating your own homegrown mushrooms in 2–3 weeks. Give it a try, and let us know how your mushroom-growing journey goes!
