How to Grow Portobello Mushrooms in Two Ways (Indoors and Outdoors): A Beginner’s Guide

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Learning how to grow portobello mushrooms are a fun way to get started out on gardening as a hobby. Unlike other more complicated plants and mushrooms, portobellos are not as high-maintenance. You can grow these large mushrooms indoors or outdoors. You just want to make sure you have the right materials and gardening tools to properly grow them, and not to mention the right temperature to keep them healthy.

What Are Portobello Mushroom?


Freshly-harvested portobello mushrooms are loaded with a lot of nutrients good for your health.

Believed to be one of the largest types of mushrooms, the Portobello can grow up to six inches. What physically sets it apart from other mushrooms (aside from its size) is its distinctive gills that look like webs just under its cap. Because of this characteristic, it was scientifically named, Agaricus bisporus– the word agaricus translating to gilled mushroom. Smaller versions are called crimini.

sign to identify portobello mushrooms

The gills are a good sign to identify portobello mushrooms.

Widely recognized as a superfood, portobellos are large mushrooms that packs a lot of nutrients and flavor. When cooked, these mushrooms can be really succulent and just overall delicious. Because of its tender and meaty texture and flavor, especially when grilled, the portobello mushroom is often served as an alternative to ground beef patties in burgers.

portobello mushroom recipes

A vegetarian burger can be served with a portobello mushroom patty- a healthier alternative indeed!

Portobello mushrooms are loved by both amatueur and professional kitcheneers for their versatility. Aside from being a delicious alternative to meat in vegan burgers, these mushrooms are a great addition to casseroles, omelettes, salads, pasta, and soups. Preparing portobello mushrooms in exquisite dishes is quite the experience, and it just makes sense that a lot of people enjoy growing them as much as they enjoy cooking and eating them.

Baked and stuffed

Baked and stuffed portobello mushrooms are perfect for vegan parties.

In this article, we will be filling you in on how to grow portobello mushrooms in your very own garden. But before we proceed, let us first learn about the mushroom life cycle in order to get a better understanding of how these large button-like food chameleons grow.

Mushroom Life Cycle

mushroom life cycle

Mushrooms usually multiply through spore germination

Unlike plants, mushrooms do not grow from seeds, but rather from very tiny spores. Producing them isn’t exactly the same as planting common fruits and vegetables. In order to germinate, the tiny spores from which they come out of require nourishing materials such as grain, wood chips, straw, sawdust, and liquid to keep them healthy. The spores and these special nutrients synthesize into what is called, a spawn.

Mushroom spores synthesize to form spawns.

Mushroom spores synthesize to form spawns.

Spawns are responsible for the growth of mycelium–the mushroom’s tiny, stringy roots. While it is very much true that untreated spawns are capable of producing mushrooms, adding a growing medium or substrate can enhance the quality of the harvest by a mile. These can be straw, cotton, wood chips, cardboard, and even treated compost.

How To Grow Portobello Mushrooms Indoors

If you’re eager to turn growing portobello mushrooms into a hobby, you’re going to love and prefer indoor production. Mushrooms don’t have chlorophyll, which means they don’t get any nutrients and energy from the sun. You just have to keep them at the right temperature– 18-21 Celsius. For this method, you’re going to need the following materials:

  • Portobello mushroom spores
  • Compost
  • Damp moss
  • Tray (preferably 4×4 feet and 8 in deep)
  • Newspaper
  • Water


  1. To create the bed, fill the tray with 6 inches of compost. Sprinkle the portobello mushroom spores across the bed, and work them into the compost with a gentle downward pressure.
  2. Leave the tray in a dark environment until tiny traces of white start to emerge.
  3. Add in a layer of damp moss and cover the entire bed with the newspaper.
  4. For two weeks, spray just enough water twice a day.
  5. Take off the newspaper covering and check for little white heads. If there are, you may now remove the newspaper for good. Otherwise, cover the bed with a new piece of newspaper and spray water for another week.
  6. Spray once daily when the newspaper is already taken off.
  7. Harvest when the mushrooms are large enough for your preference.
Portobello mushrooms Cooking

Portobello mushrooms are best cooked when freshly harvest.

How To Grow Portobello Mushrooms Outdoors

This method of growing portobello mushrooms is ideal for naturally green-thumbed people who prefer to stick to traditional processes of gardening. For outdoor growing, you must regularly check daytime and nighttime temperatures and make sure they don’t exceed 21-degree Celsius and fall below 10 degree Celsius. You’re going to need the following materials:

  • Portobello mushroom spores
  • Compost
  • Damp moss
  • Cardboard
  • Water


  1. Construct a bed from common building materials like wood. It should be 8 inches deep and 4×4 feet in dimension.
  2. Fill the constructed bed with around 5-6 in of compost.
  3. Cover the compost surface with cardboard and the bed with black plastic to promote solar radiation. This process sterilizes the entire bed. Leave it for two weeks.
  4. After two weeks remove the cardboard and black plastic coverings and sprinkle the spores across the compost and work them in while tapping lightly. Again leave it for two weeks.
  5. After another two weeks, the mycelium will start to emerge from across the surface. Add an inch-layer of damp moss across the surface, and cover with a newspaper.
  6. Water twice daily for ten days.
  7. Harvest when the mushrooms are large enough for your preference.


Mushrooms grow best in dark, humid environments. If you’re planning to grow your portobellos indoors, you’ll find your basement ideal. If you don’t have a cool, dark, and moist basement, you can always place your tray bed under the sink. Ideal temperatures for growing mushrooms vary for each type, but most of them grow well at 12-21 degrees Celsius. Growing mushrooms is ideal in the wintertime when these conditions are met.

how to grow mushrooms

You can grow mushrooms in your basement or under your kitchen sink.

Meanwhile, some types of mushrooms grow naturally, with or without added nourishment from a water sprinkler or fertilizer, in logs or on the ground if the temperature is ideal. This process takes six months to three years, a much longer growing period as compared to the easily controllable conditions indoors.

Now go forth and start that mushroom-growing hobby you’ve always wanted to try. We hope that this article has equipped you with more than enough information on how to grow portobello mushrooms for you to have an enjoyable and rewarding time. Thanks for reading!

Lucy Author
Hi there! I’m Lucy – founder of GardenAmbition.com and I’m a self-confessed garden fanatic. Gardening has always been a passion of mine and will always be my favorite pastime. Now that I am married and have one adorable son, I have the time to write and share my personal experiences with other garden enthusiasts like me.


Jonathan E. Bass

Graduated from Middle Tennessee State University. I am currently a gardener. I have a small garden behind my house. I love it.

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