Growing Mushrooms Outdoors: The Simplest Methods

Cultivating mushrooms is a popular hobby. Many growers choose to do it indoors to control the environment carefully. However, growing mushrooms outdoors has many advantages too. In fact, since mushrooms naturally grow in the open air, some people consider it a better option.

There are many different methods for cultivating mushrooms outdoors. In this article, we discuss three of the most popular techniques:

  • Growing oyster mushrooms in bags
  • Creating a dedicated mushroom bed
  • Growing mushrooms on logs

We also discuss the benefits and possible pitfalls of growing mushrooms outside. Here’s everything you need to know.

Growing Mushrooms Outdoors

Growing mushrooms outdoors is very different from cultivating them inside. However, many of the requirements are the same. To get started, you will need:

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  • Mushroom spawn
  • A nutrient-rich substrate (wood, straw, etc.)
  • A source of water

The other equipment required depends on the growing method, and some are more involved than others. Let’s look at each option in more detail so you can decide which best suits your needs and experience level.

Growing Oyster Mushrooms in Bags

Oyster mushrooms are one of the most straightforward varieties to grow and are ideal for beginners. They are robust and adaptable, and you can grow them on numerous substrates. However, one of the simplest methods is growing oyster mushrooms outdoors in bags.

You will need:

  • Oyster mushroom spawn
  • Straw
  • Water
  • A large container for soaking and mixing
  • Black polyethene bags

Note: It is crucial to choose straw rather than hay, which is more prone to contamination.

Step 1: Prepare the Substrate

Place the straw in the container (a clean dustbin or large bucket is ideal) and cover it with water. Soak it for 24 hours, then drain off the excess water.

Step 2: Inoculate

Add the mushroom spawn to the straw and mix it thoroughly to distribute evenly. One pack of mushroom spawn should be enough to inoculate 3–5kg of straw.

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Step 3: Incubate

Pack the inoculated straw into the bags and tie off the tops. Place the bags in a moist and sheltered spot for six weeks. The ideal incubation temperature is 70–80 degrees Fahrenheit. Try placing the bags close to a compost heap if you need additional heat.

Step 4: Initiate Fruiting

After six weeks, check on the bags. You should see that the straw has been thoroughly colonized by white mycelium. Mushroom pins may even be starting to form. This means it is time to initiate fruiting.

Move the bags to a light, warm, and moist area. A greenhouse is ideal, but you can also leave them outdoors if the conditions are favorable.

Using scissors or a sharp knife, slit the sides of the bags. Space the slits out evenly, leaving a few inches between each one. You should see clusters of beautiful oyster mushrooms starting to appear through the slits within a couple of weeks.

Step 5: Harvest

Harvest the mushrooms when they have reached full size, and the caps are just beginning to curl upwards.

Creating a Dedicated Mushroom Bed

Another option is to create a mushroom bed in your garden. You can dig down to make a bed level with the surrounding soil or build a raised bed, which many growers prefer. Raised beds have the advantage of providing a distinct border for your mushroom bed. They also mean less bending when it comes to harvest time!

A mushroom bed is particularly suitable for king stropharia (also known as wine caps or garden giants) and oysters.

Many different mushrooms can grow in this type of set-up. However, it is particularly suitable for king stropharia (also known as wine caps or garden giants) and oysters.

Although it is also possible to grow white mushrooms in this way, it is not usually recommended.

This is because some poisonous species have a very similar appearance. So, if a rogue spore blows into your bed, you could be in trouble.

You will need:

  • Mushroom spawn (approximately 3kg per 4m2)
  • A large sheet of cardboard
  • Woodchips (see below)
  • Straw
  • Shade netting (optional)

Note: Choose untreated hardwood chips and check that the pieces are not too large. You should also ensure the chips are not too old. Older woodchips could already be infected with other fungal species that will compete with your mushrooms for nutrients.

Step 1: Prepare the Bed

After digging your bed, cut the cardboard sheet to size and use it to line the base. This will help retain moisture and suppress the growth of unwanted weeds.

Step 2: Add the Substrate and Spawn

The next step is to add a 1–2 inch layer of the substrate on top of the cardboard. Woodchips are a popular option as they provide plenty of nutrition for hungry varieties like king stropharia. It is also possible to use straw if you grow oyster mushrooms in your beds.

Next, add half of the mushroom spawn and spread it evenly over the substrate. Then add another layer of woodchips and spread them evenly over the spawn. Repeat the process, finishing with a layer of woodchips. Finally, top off the bed with a layer of straw. This will help to retain moisture and keep the bed warm.

Give the whole bed a good soak, but not so much that you end up with puddles of standing water.

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Step 3: Incubate

It can take several months before the mushrooms are ready to harvest. The bed must be kept moist during this period to prevent the mycelium from drying out. Therefore, watering the bed at least weekly is essential, although this is not necessary during rainy weather.

Some people use shade netting to reduce water loss. You could also consider building your bed in a naturally shaded area, for example, under a tree.

After a couple of months, you may see white mycelium starting to develop. Then, after six months or so, your first mushroom pins should begin to form. Remove the shade netting (if using) at this stage.

Step 4: Harvest

It is important to harvest the mushrooms before the caps flatten out fully. If you leave them too long, they can begin to deteriorate or become infested with insects looking for a free meal.

Step 5: Feed Your Bed

A mushroom bed can continue to be productive for many years. Once you have finished harvesting the first flush, feed the bed with more woodchips, using a rake to mix them with the established mycelium.

Remove any weeds manually and avoid using pesticides or other chemicals on your mushroom bed. Mushrooms are bio accumulators, meaning they can easily absorb contaminants from their environment. Growing mushrooms outdoors is definitely a scenario where organic is best!

Growing Mushrooms on Logs

Growing mushrooms on logs is another popular outdoor cultivation method. It involves inserting impregnated wooden dowels (plug spawn) into holes in logs, which provide nutrition for the growing mycelium.

Hardwood logs are best, and the optimal variety depends on the mushroom species you wish to grow.

Hardwood logs are best, and the optimal variety depends on the mushroom species you wish to grow. For example:

  • Shiitake: Prefers oak or maple.
  • Oyster: Prefers white birch.
  • Lion’s mane: Prefers beech, elm, poplar, or maple.
  • Reishi: Prefers oak or plum.

Other tree species may be suitable, but avoid conifers, sycamore, apple, and ash as these are less suitable for fungal growth.

You will need:

  • Mushroom plug spawn
  • Logs (see note)
  • A drill
  • A hammer
  • Food grade wax (cheese wax, beeswax, etc.)
  • A heat source and container for melting the wax
  • A wax dauber (this can be a piece of cloth attached to a stick with elastic bands)

Note: The logs should be cut from a healthy, dormant tree between late fall and early spring (once the tree has lost its leaves). Inoculate the logs within a month as older logs may become infected with other fungal species. It is also best to keep the bark intact to reduce the risk of contamination and help retain moisture.

A final consideration is the size of the logs themselves. Larger logs will support more fungal growth and produce mushrooms for many years to come. They also retain moisture better than smaller logs. However, you want them to be portable, so don’t select logs that are so large they are difficult to move. An ideal size is approximately 6–8 inches in diameter by 3–4 feet in length.

Step 1: Inoculate the Logs

Drill holes in the logs ready for the plug spawn. Ensure that you use the right drill bit to make big enough holes to fit the plug spawn snugly inside. You want the plugs to be flush with the surrounding wood so that the mycelium can spread to the log quickly. Space the holes around 6 inches apart, with 3 inches between rows.

Insert the plug spawn into the holes and tap it gently with the hammer, so the dowels are flush with the log’s surface.

Heat the wax to melt it. You could use an old pan on a camping stove or simply stand a tin can in some hot water. Once the wax is melted, use the dauber to apply it over the plug spawn. Seal the holes completely to prevent contamination and retain water. Seal any other damaged areas of bark, but leave the ends of the logs unsealed.

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Step 2: Incubate

It can take 6–18 months to colonize the logs fully. During this time, keep them in a moist, shaded area to prevent drying out. If you notice that the logs are becoming dry and the bark is cracking, soak them in water for a couple of days to wet the bark thoroughly.

Some people keep the logs wrapped in polyethylene during the incubation period to retain moisture.

Step 3: Shock the Logs to Initiate Fruiting

This step is optional, but it can significantly speed up the fruiting time. Without shocking the logs, they may take as long as 2–3 years to fruit!

When the logs are around 8–14 months old, you should see signs of colonization at the ends. At this stage, you can shock them into fruiting by soaking them in cold water for 24 hours.

Some growers also recommend knocking the logs with a hammer to activate the mycelium.

After shocking them, place the logs in a warm, moist, sheltered area with dappled shade to fruit.

Step 4: Harvest

Small white nodes will appear at the inoculation points when the mushrooms are ready to fruit. These will develop into mushrooms, sometimes in as little as a week (depending on the variety).

Keep the logs moist and avoid moving them during the fruiting period, which can last several weeks. After a few months, they should produce a second crop and may continue fruiting twice a year for up to five years.

Harvest the mushrooms while they are young and fresh. You can store them in a refrigerator for several days or dry them if preferred.

The Benefits of Outdoor Mushroom Growing

Outdoor grows are generally simpler than indoor grows. They rely heavily on the elements, making it less labor-intensive overall.

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Growing mushrooms is also great for the soil, and some species form symbiotic relationships with garden plants to aid their growth. If you have a sickly-looking lawn or some barren flowerbeds, why not try planting some mushrooms there instead?

Another benefit is that outdoors, mushrooms are exposed to natural sunlight. This boosts their vitamin D content and makes for an even healthier harvest.

What Can Go Wrong?

Although outdoor grows rely less on technology than indoor grows, they are not immune from problems. In fact, they can be even less consistent than indoor grows as the environment is not as tightly controlled.

If your outdoor grow fails, consider the following factors:

Contamination

Contamination is a significant issue with indoor grows. Although it may be less of a problem outdoors, it can still happen. It is always important to use fresh woodchips, logs, or straw to reduce the likelihood of contamination by competing organisms.

Inappropriate Moisture Levels

The mycelium must remain slightly damp throughout the growing process. However, too much moisture can increase the risk of mold. Provide ample drainage and do not overwater your project so that you have stagnant, standing water.

Insufficient Air Exchange

This is not usually an issue outdoors. However, it may be best to avoid growing in very sheltered areas where there is no breeze at all.

Low-Quality or Expired Spawn

Only purchase mushroom spawn from reliable companies that have a minimal shipping time. Once your spawn arrives, use it as soon as possible to reduce the risk of contamination or mycelium death.

Other Considerations When Growing Mushrooms Outdoors

Growing mushrooms outside is relatively simple, but there are a few factors to consider to ensure a successful harvest:

Timing

Unlike indoor growing, outdoor cultivation relies heavily on the seasons. It is possible to start growing anytime between spring and fall, depending on your location and the species you are growing.

However, the mycelium must have time to establish itself before freezing temperatures set in. Therefore, most growers in temperate regions start by May at the latest.

Mushroom Variety

Not all mushroom species are suitable for growing outdoors in every climate. For example, someone living in a cooler region will not likely have success growing tropical varieties and vice versa.

Location

It is essential to choose the location of your mushroom grow carefully. It needs to be easily accessible so that you can check up on your logs or beds every couple of days. It also needs to have access to a water source since moisture is critical.

Identification

When growing mushrooms outdoors, it is vital to identify every specimen before consumption. There is always the possibility that a poisonous mushroom spore could infiltrate your bed, so be aware of this when harvesting.

Growing Mushrooms Outdoors: Summary

There are many ways to grow mushrooms outdoors, including in bags, dedicated beds, or on logs.

Growing mushrooms in this way has many advantages, and it is rewarding to see your fungi develop in their natural habitat. However, there are also some unique challenges to consider to produce a bountiful yield.

Do you have any tips for successfully growing mushrooms outdoors? Please feel free to share them with our community in the comments below.

Now you’re ready to start growing mushrooms outdoors, which variety should you choose? Learn about some of our favorites below:

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