If you’re trying to save money but still want fresh, good-quality food, learning how to grow oyster mushrooms at home is a great place to start. You don’t need fancy equipment or loads of space—just some cardboard, straw, and a bit of time. I’ve used this method myself many times, and it’s one of the simplest, most affordable ways to grow your own mushrooms.
This guide is for anyone—students, people on low incomes or benefits, or anyone trying to eat well without spending loads. Oyster mushrooms are quick to grow, taste great, and can be grown in a tiny space using materials you probably already have lying around.
Why Use Cardboard and Straw?
Cardboard and straw are cheap (or free), and they work really well for growing mushrooms. Cardboard makes a great base for creating your own mushroom spawn, and straw is a reliable material to grow mushrooms on once your spawn is ready. You don’t need to sterilise anything or work in a lab—this is a low-tech, no-fuss way to grow food.
Step 1: Make Mushroom Spawn Using Cardboard
What is spawn?
Think of spawn as the seed you use to grow mushrooms. Normally, people buy spawn or grow it using sterilised grain, but I make it using cardboard and pieces of oyster mushrooms. It’s cheap, simple, and works well.
What you’ll need
- Clean cardboard (no tape or printed ink)
- A container with a lid (like a food tub or bucket)
- Boiling water
- 70% isopropyl alcohol or alcohol-based hand sanitiser
- Oyster mushrooms (shop-bought, foraged, or home-grown)
How you create spawn
- Tear the cardboard into small pieces and place them in your container.
- Pour boiling water over the cardboard to soak and pasteurise it. Put the lid on and let it cool.
- Once cool, squeeze out any extra water—the cardboard should be damp, not dripping.
- Tear the mushrooms into small bits.
- Layer the mushrooms and cardboard like a lasagne—start with cardboard, then mushrooms, and repeat.
- Press the layers down gently and close the lid.
Keep the container somewhere dark and warm (around 18–23°C). Every few days, open the lid and fan in some fresh air. After about 2–3 weeks, the cardboard should be covered in white fuzz (that’s the mycelium), and your homemade spawn is ready.
Preparing a grow bucket with pasteurised straw and cardboard spawn
Once your spawn is ready, you can move on to growing the mushrooms.
Step 2: Grow the Mushrooms on Straw
What you’ll need:
- Straw, chopped into short pieces (about 5cm)
- Another clean container or a mushroom grow bag
- Boiling water or hydrated lime (for pasteurising)
What to do:
- Pasteurise the straw just like you did with the cardboard—soak it in boiling water, then let it cool and drain.
- Layer the straw with your cardboard spawn in a clean container or grow bag.
- This container should have small holes or filtered patches for air. If it doesn’t, poke a few holes and cover them with micropore tape.
Keep it warm and dark again for a couple of weeks. Once the straw is fully colonised and covered in white mycelium, it’s time to fruit your mushrooms.
Fruiting: The Fun Part
Move your container somewhere cooler—kitchens usually work well. If your container has holes, mushrooms will start pushing out on their own. If not, cut an ‘X’ in the bag to give them space.
Spray the area around the holes 3–4 times a day to keep humidity high. After 1–2 weeks, you’ll start to see pins (baby mushrooms) forming. Let them grow for about 5–7 days until the caps start to flatten out. That’s the best time to harvest. Just twist the whole cluster off.
Keep the bag moist and you’ll usually get a second flush, sometimes even a third.
Final Thoughts
I’ve been teaching about growing mushrooms this way for years, and it still amazes me how much you can grow with so little. If you're on a budget and want better food, this is a simple place to start. Plus, there’s something really satisfying about eating mushrooms you grew yourself from a bit of cardboard and a leftover tub.
