In this guide, I will show you how to grow oyster mushrooms in outdoor straw beds. I used store-bought sawdust spawn from North Spore to make my oyster mushroom straw beds. This is a fantastic, fairly simple process that I would recommend for any fungi farmer beginners. Fruiting time is rather quick, and you can grow oyster mushrooms in straw beds during the spring, summer, and fall. Keep in mind that various Pleurotus species (oyster mushrooms) have different fruiting range temperatures. Thus, cooler fall weather temperatures favor certain species fruiting. In contrast, some oyster mushrooms prefer warmer summer temperatures. For this project, I prepared golden oyster mushroom straw beds, a good summer-fruiting species. However, you can apply these general methods to any oyster mushroom species.
Materials You Will Need to Grow Oyster Mushrooms in Straw Beds
- Organic Wheat Straw, enough to fill one laundry basket and one milk crate, loosely compact
- One or two laundry baskets and/or three-four milk crates (optional), thoroughly cleaned/disinfected
- Coco coir, about 0.5 cubic feet (optional)*
- Pulverized lime or hydrated lime, 3-5 cups
- One mixing tub (optional, see below for details)
- Scissors/something to chop straw
*Note: Although oyster mushrooms can grow in a pure straw substrate, straw has a low nitrogen content. Thus, for optimal results, it is useful to supplement straw with other substrate materials. See Grocycle’s article here for a comprehensive guide to mushroom substrates.
Preparing Your Straw Substrate to Grow Oyster Mushrooms
If you are cultivating oyster mushrooms outdoors, you are not required to treat your substrate. However, if you are growing mushrooms indoors, chances of substrate contamination are much higher. Thus, people will pasteurize or sterilize their growing substrate for indoor cultivation. Regardless, I decided to go the extra mile and do cold water lime pasteurization for my substrate. I found this simple but effective process at GroCycle. First, I placed several handfuls of pulverized lime in a large plastic tub filled with clean, potable water. Then I chopped up my straw into various lengths, including 3-4″ bits, and put them in the tub. For the whole tub, I probably filled it with 66 to 75% straw: 25 to 33% coco coir. I let the substrate soak for 24 hours, weighing it down with a bag of soil. During this time, the lime raises the pH of the substrate, killing contaminants.
Next, drain the water from your straw/coco mix. I took handfuls of substrate and squeezed until only a few drops of water came out. This took me maybe three hours to do. North Spore has a slightly more high tech but also more efficient way to drain your straw. I placed the drained substrate into one laundry hamper and one milk crate, both cleaned with an all-purpose cleaner. For outdoor straw beds, it is optional to use these containers. I chose to use them to keep my beds contained. Of course, they’re also good for transporting if your straw beds will end up in a different location from your prep location. I let the straw bed mixture sit outside overnight as I was short on time.
Assembling Your Oyster Mushroom Straw Beds
When you are ready to proceed, gather your oyster spawn, straw or straw/coco mix, containers (if using), and a water mister or small watering can. The basic layering methods I am about to discuss I obtained from North Spore. Remember, your substrate is already wet (if you pasteurized your substrate), so you only want to moisten the spawn. If transporting your spawn to another location for your straw beds, keep it in a cooler with an icepack.
To start, pick a shady location out of direct sunlight for your oyster mushroom straw beds. Once you’ve settled on a good spot, loosely disperse your first layer of straw or straw/coco on the ground or in your laundry bin. You want good coverage but to also have the straw distributed so there are a lot of air pockets. The fungi you are growing needs some good ol’ oxygen. Then you will break your spawn up into small bits and add your first layer of spawn to your straw bed. Next, mist or lightly water to moisten your spawn layer. If you skipped the pasteurization step, no worries! Just be sure to water every layer of straw and spawn. I would water each layer as I add them, rather than all at once.
Here I have half-way completed my straw bed. There are alternating layers of straw/coco and spawn, with the spawn layer currently on top. Some of my hunks of spawn are on the large side. There is no wrong size. You can stretch out your spawn to more containers or larger straw beds with smaller chunks. However, if you are new to this process, it is better to err on the side of using more spawn then less. I would avoid putting spawn directly against the container side holes if using a container. The spawn is more likely to dry out and go to waste.
The final top layer needs to be, you guessed it –more straw. Protect the young spawn babies from drying out! Mist or water this top layer, especially if you skipped the pasteurization step. During the first two weeks, it’s crucial to keep the straw beds moist but not oversaturated. If the beds dry out, the fungus will die. If the beds are over-watered, mold and bacteria will take over. During hot, dry days, mist the beds thoroughly, once daily.
Watch for Signs of Life and Harvest
Now this is the ooh-ahh part that makes all your efforts worth it. OK, harvesting and eating your own mushroom crop definitely makes it all worth it. But watching these babies grow is a sight to see, people! I prepared my oyster mushroom straw beds on July 24. Only twelve days later, on August 4, young fruiting bodies were first sighted. I honestly didn’t think they’d fruit that fast, and they were not in a location I could check daily, but almost daily.
This is the same straw bed only two days later (August 6), and ready to harvest! A collection of mushroom or fungus fruiting bodies ready to harvest is called a flush. Often, you can get multiple flushes from your inoculated substrate.
This is my larger straw bed, the same day that the straw bed above was ready to harvest. This one has younger fruiting bodies, not yet ripe for picking.
The very next day, my larger straw bed’s oyster mushrooms were ready to harvest!
There was a small learning curve to know when to harvest the oyster mushrooms. In the image directly above, I waited one more day to harvest. All the larger fruiting bodies looked slightly less fresh (but still worth eating). The tiny fruiting bodies did not get any larger, and they started to shrivel a bit. Again, they’re still usable, just not at peak harvest. Twenty days after my first flushes, both my straw beds produced second flushes. I was a day or two late to pick them, but they were still perfectly good. Sixteen days after the second flush, my smaller straw bed produced a third flush (nothing yet seen in the larger straw bed). These also appeared to be a day or two past peak harvest. Noticing a pattern? Stay on top of your flushes! They wait for NO ONE. Not even their inoculation parents! I digress.
If you’re interested in a method of growing oyster mushrooms indoors, check out my article about that here.