Let’s face it, growing mushrooms can be complicated. You have to worry about managing cultures, sterilizing grains, making spawn, mixing substrates and trying to do it all without introducing contamination that could ruin your whole project. Of course, if you love growing mushrooms as much as I do, all those complicated terms sound like music to your ears! But if you are new to the process you might just be asking yourself: “Isn’t there an easier way to grow mushrooms from scratch?” Of course, you could always try growing mushrooms from a kit… but if you wanted to have a much more satisfying experience, you might want to consider growing mushrooms outside in a straw bed. It’s actually pretty easy to do. Using pre-made spawn, you can grow oyster mushrooms outside with:

In fact, to grow mushrooms outside, all you really need is some pre-made grain spawn, a bundle of wheat or oat straw, a sheet of poly or tarp, and water. I love growing mushrooms like this, and try to have a garden bed or two fruiting mushrooms throughout the spring, summer and fall.

Keep in mind though, although this method is easy, there’s really nothing magic about it. You’ll get mushrooms, but you aren’t going to get the same predictable results you would if you were to grow from properly colonized substrate in a highly controlled environment. But- you are very likely to succeed in growing more mushrooms than you’ll know what to do with, without going through much trouble at all. Let’s go through the process step by step.

What You’ll Need

1. Grain Spawn You can either make the grain spawn yourself, of buy pre-made grain spawn. Making your own grain spawn is certainly awesome (I highly recommend trying!) but it is not all that beginner friendly. There are many great places that you can buy pre-made grain spawn online. If you live in the USA or Canada, you can even get it from FreshCap. 2. Straw You can use either wheat straw or oat straw. The best bet is to find a local source of straw. If you live anywhere near a farm you’ll find that many farmers are almost giving it away. In my area, I can get a 40lb bale of straw for $3. If you can’t find a local source, you can always but some on Amazon. 3. A Sheet of Poly You’ll need something to put over the mushroom bed after you inoculate it so that it can stay moist and protected while it is colonizing. You could also use a tarp. 4. Some Space in the Garden Of course, you’ll also need some room in the garden. Try to find a spot that gets the least amount of direct sunlight. A perfect spot is somewhere that gets shade all day, surrounded in tall grass or bushes that can help keep the humidity up.

Choosing Your Mushroom

The kind of mushroom you choose to grow will have a huge impact on your results. Ideally, you want a species that grows fast on straw, and is resilient enough to withstand fluctuating conditions. If you live in a temperate climate, Blue Oyster is a great choice since it grows fast and fruits heavily on straw, while it is pretty good at fighting off competitors. If you live in a warmer climate, you are better off sticking to tropical species, like Pink or Yellow Oyster. Stay away from Shiitake, or the wood loving species like Lions Mane or Reishi, as chances of success with this method is low.

Time of the Year

The ideal time of year to have an outdoor mushroom garden is obviously going to depend on where you live. Living in central Alberta, I like to start the Oyster garden in late April, which will give the best chance to get a couple fruiting throughout the season. If you start your garden later in the summer or fall, you will likely only get one flush before winter. In warmer and drier climates, starting in the middle of summer will likely not produce great results, if any. Just keep in mind that most mushrooms prefer a cool and humid environment, and try to match time your grow with the proper environmental conditions.

Step 1: Clear out an area for your garden.

5 lbs of grain spawn will cover about 18-20 sqft of garden space. Make sure that the area is reasonably clean and level. If you are making the bed right on grass, you may want to consider digging out the grass or placing some landscaping fabric over it so that the grass doesn’t just take over. I decided to just use a few large pieces of cardboard to lay down under the bed. For my oyster garden bed, I chose an approximately 3 ft x 6 ft (18 sqft) area surrounded in tall grass and trees. I dug out the grass and weeds and flattened everything. I also laid down some 4 x 4’s and cinder blocks to define the edges of the garden. Nothing fancy that’s for sure, but it does the trick!

Step 2: Layer the Straw and Spawn

Place a thin layer of straw down (about 1-2” thick), covering the whole area of the garden bed. Then, take your grain spawn and sprinkle down a thin layer evenly throughout the whole bed. Make sure there are no clumps in the spawn, and try to spread it out as evenly as possible. You will want to repeat this process, layering straw and spawn, about 3-4 times until you are out of spawn. As mentioned earlier, you’ll want to use about 5 lbs of spawn of every 18-20 sqft of garden space. You can certainly use more if you wanted to, although you will see diminishing return pretty quick. Also, don’t spread the spawn too thin, as you’ll need a threshold level of spawn for it to fully colonize the straw and produce results. Once you are out of spawn, place a thin layer of straw down on top to cover the entire bed for the final layer. Make sure there is no large area of exposed spawn.

Step 3: Soak and Cover

After the final layer of straw has been placed down, take a garden hose, and give the straw bed a good soaking. The spawn needs moisture in order to proper grow and colonize the straw. In order to ensure the bed stays moist, cover it with a sheet of poly, or a tarp. You could try and skip this step, but it will definitely lower your chances of success. The spawn also needs to breath- so be sure to cut some holes in the poly to allow for air exchange. If you have a nice tarp that you don’t want to cut holes in, you’ll have to open it up at least a couple times a day to allow it to breath (which makes the sheet of poly a much better option).

Step 4: ….Wait

This is always the hardest part about growing mushrooms. You’ll probably have a tendency to check it every day, but this is totally unnecessary. That being said, make sure you at least take a quick look at the bed once a week. If you are experiencing hot and dry weather, you may need to check it more frequently. I like to remove the poly once a week to check if the bed is still moist. If it’s dry to the touch, give it a good spray down with a hose in order to re-hydrate the substrate. You can also check to see if your spawn has started to grow through the substrate. Healthy mycelia growth should be pretty obvious. Simply pull back a small section of the top layer of straw, and you should see new white growth slowly working its way across the straw. Once the mycelium has completed its expansion through the straw, you should start to see pins and little clusters of mushrooms poking through to the top. This often takes 3-4 weeks from inoculation, but depending on your climate and time of year, the process could take longer.

Step 5: Harvest!

Once a nice set of pins appears across the bed, it’s time to remove the poly and let your mushrooms grow into full sized fruits. This is the best part of growing mushrooms! The fruits will grow extremely fast at this point, so make sure you are checking it every day to ensure you harvest at the right time. In my opinion, the best time to harvest oysters is just before the cap starts to curl up. Harvesting them a little earlier is also a good way to fend off the bugs that will try to burrow into your mushrooms. I prefer to harvest entire clusters at once instead of picking individual mushrooms. This also prevents excessive damage to rather delicate fruits. Harvest the entire bed at once, after the first “flush”. This way, you can just rehydrate, cover the bed back up and wait for the second flush. Again, depending on the climate, you should be able to get multiple “flushes” of mushrooms throughout the season, sometimes up to four flushes from a single bed.

Potential Problems

As mentioned earlier, although this is the easiest way to grow mushrooms, you can’t really expect the same results as when growing mushrooms in a sterile and controlled environment. You are likely to run into some problems along the way. 1. Bugs Bugs love mushrooms, and will not hesitate to burrow their way into the stems at the first sign of a fruit. Given enough time, the bugs may lay eggs in the mushrooms, which will hatch quick and make for an unpleasant surprise when you cut your mushrooms open. The best way to combat this is to harvest your mushrooms at the right time, before the bugs really get a chance. You could also consider getting a fine mesh and setting up a “hoop house” over top of the mushroom bed. 2. Invasive Species Of course, there is always the possibility of another species of mushrooms growing in the straw bed along with, or in place of, your intended species. Although it should be pretty easy to tell the difference, make sure you pay close attention to what you are harvesting. You wouldn’t want to accidently harvest and eat a potentially harmful species. 3. Weather Unfortunately, we don’t have complete control of the weather. If you run into a period of extreme weather- hot and dry, freezing temperatures or even excessive rain- the mushroom may die before it gets a chance to fruit. You can minimize this risk by putting your garden bed in the most suitable location and by trying to time your grows with the seasons in your area. 4. Contamination When growing mushrooms outside like this, it is only a matter of time before competing molds and fungi start to grow on the substrate. This is a sign that the mushroom bed is past its prime. You may start to notice this in small patches at the edge of the mushroom bed, or where there is patches of exposed grain. At this time, it’s probably best to remove the straw and toss it in the compost before starting a new bed.

Your Very Own Mushroom Garden

Growing mushrooms outside using this method is a relaxing and totally rewarding way of producing wonderful food at home. It is also a good way to get an understanding of the mushroom life cycle and to get the experience of growing mushrooms without the investment of specialized equipment and more complex methods. If you have an adequate place in your yard, I would highly recommend you give it a try!