How To Grow Portobello Mushrooms: All You Need To Know

how to grow portobello mushrooms

Are you an avid gardener who loves to try growing and experimenting with new crops every week? If so, then maybe you would be interested in trying out planting, cultivating, and harvesting Portobello mushrooms. Large and succulent, this particular type of edible fungus makes for a great recipe, especially a hearty, vegetarian burger for your next meal.

That said, how can you get started? We are here to help! Learn more in this article on how to grow Portobello mushrooms in your backyard, from start to finish. Soon enough, you will be able to get them to your dinner table for you and company to enjoy.


Things You Will Need For This Tutorial​

Things You Will Need For This Tutorial

Even though there are varying options when it comes to growing Portobello mushrooms (or any mushroom, for that matter), more or less there are just a few, basic ingredients that you will need to get started. Here are some items you will obtain for your mushroom-growing experience:

#1. Mushroom Spores

Mushroom Spores

While it is possible purchase mushroom spores in an already-prepared kit at your local gardening and hardware store, you can also cultivate them from scratch in that you use a spore print to catch and trap the spores from the actual fungus itself. Having these spores is one step to growing your Portobello mushrooms.

​#2. Compost​

Fungi such as mushrooms thrive on rich compost, especially that of manure-based. Similar to vegetable fertilizers, compost is made from a complex blend of different natural elements and ingredients, of which will enrich and activate the spores in order to grow big and healthily.

​#3. Garden Bed

Garden Bed

Especially if you will be growing your Portobello mushrooms outside, preparing a garden bed is the way to go. Ideally, it will need to be raised to allow for easier draining and management.

​#4. Cardboard​

This piece of hard paper will be used with the garden bed for outdoor cultivation. This is to create a sort of solar radiation that sterilizes the garden bed, so that later the mushrooms can grow efficiently without any contamination from outside sources.

​#5. Peat Moss​

Peat Moss

On the other hand, if you plan to grow Portobello mushrooms indoors, then peat moss will serve you best. It has an acidic pH, so it works well as a soil amendment to growing acid-loving plants and fungi, including mushrooms. You can choose to purchase peat moss as is, or you can try your hand at growing it from our article on how to grow moss indoors.

#6. Newspaper​

Likewise with peat moss, you will use newspaper to grow Portobello mushrooms indoors. You might wonder just what is the function of newspaper, but what it really is used for is mulching. In other words, it is a sort of decomposing product to help feed nutrients into the soil for better cultivation.

​#7. Tray​

Just like a garden bed, a tray is used for containing the mushroom spores whilst growing indoors. It is a good idea to check the dimensions beforehand, to make sure that it is big and deep enough to contain everything you need.

​#8. Water​

More specifically, you will need all but a bit of water (think mist) to keep your mushroom spores in damp soil. Considering that they are fungi and not plants, watering them excessively will do excessive damage, rather than helping them.

Step-by-Step: How To Grow Portobello Mushrooms​

As mentioned in the items section, you can choose to grow Portobello mushrooms one of two ways: indoors or outdoors. Whichever option you go with, keep in mind that they are similar to each other, more or less. Here are the steps for both processes:

#1. Outdoors​

1. Check The Temperature

Considering that you will be planting your mushroom spores outside, it is important to make sure that the temperatures are ideal for them to grow in. As a rule of thumb, it is best to cultivate them in temperatures that are no lower than 50 degrees Fahrenheit (10 degrees Celsius) and no more than 70 degrees Fahrenheit (21 degrees Celsius).

It might help to have a thermometer to keep things in check and know what to do if the weather is too extreme.​

2. Build Your Garden Bed

In your backyard garden, construct a raised bed that is about 4 feet by 4 feet by 8 inches deep. You may use wood, brick, stone, or any other solid items to contain the bed; with a bit of constructing, it should be a simple task that will pay off in the long run.

3. Add The Compost

Add The Compost

Place between 5 and 6 inches of manure-based compost into the garden bed and cover it with the cardboard (and black plastic, if necessary). Again, this will create solar radiation that will sterilize your bed, preparing it for successful mushroom growth. Allow for two weeks of waiting time as it does so.

4. Add The Mushroom Spores

Remove the cardboard and sprinkle in the mushroom spores. Mix them into the compost and wait a few weeks until the mycelium (thin, white film) begins to form on top.

5. Add Peat Moss And Newspaper

Once the mycelium has developed, add the peat moss and newspaper on top of the compost for enrichment.

6. Mist Your Mushrooms

Again, it is not necessary to water your mushrooms, since they are fungi and not plants. However, they thrive in damp conditions, so a light misting twice every day will cultivate them even further.

7. Harvest

After about ten days, the Portobello mushrooms are ready to be harvested. Depending on how big you would like for them to get, you can either choose to let them continue growing inside of the soil, or just pick them as soon as they are ready. It is up to you!

#2. Indoors

Follow the steps #2-6 for outdoor growing. Although it is a fact that you are growing Portobello mushrooms indoors, much of the steps are similar to that of the outdoors. The only differences are that you do not need to worry so much about the temperature, for it is easier to control inside rather than outside; ideally, aim for 65 to 70 degrees Fahrenheit (18-21 degrees Celsius).

Another difference is that growing them indoors requires a bit of patience, along with trial and error. As soon as you have misted your mushrooms, you will need to check up on them from time to time in order to see whether they have grown their small white heads yet (the equivalent of mycelium). You will need to remove the newspaper to check, as well as replace it if it is not ready yet.​

Once the small, white heads have formed, they are ready to be harvested. Follow the directions for the outdoor growing to do so.​​


Not only are Portobello mushrooms delicious to eat, but they are also quite easy to grow and harvest. Even if you have never worked with fungi before, we guarantee you that, with a bit of research and patience, you will be able to grow some of the plumpest and ripest ones out there.

Did you find this helpful? Let me know in the comments and share with someone you know!

Happy Gardening!​​

How To Grow Portobello Mushrooms: All You Need To Know
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