How to Grow Portobello Mushrooms?

Garden like a pro with this step-by-step guide on how to grow portobello mushrooms at home.

Portobello mushrooms are nutrition-rich, especially in carbohydrates, vitamin D, iron, and potassium. They are an excellent substitute for bananas and make a terrific vegetarian option for ham in burgers or steak.

Growing portobello mushrooms at home can either be outdoors or indoors. All you need are a space to put them in and a favorable condition for them to thrive.

How to Grow Portobello Mushrooms?

Growing Portobello Mushrooms Indoors

Step 1: Get a tray or container. The ideal bin depth when growing portobello mushrooms indoors is at least 8 inches.

Step 2: Fill a tray or container with manure compost with a bit of soil up to 6 inches.

Step 3: Sprinkler the portobello mushroom spores on the mixture, mix and press it lightly for the spores to settle in the compost.

Step 4: Mist the compost manure using distilled water.

Step 5: Apply a layer of peat moss on the remaining 2 inches of the container, then cover it with newspaper. It will preserve the moisture of the compost and promote mushroom growth.

Step 6: Place the container in a slightly dark room away from direct sunlight to preserve the growing bin’s temperature.

Step 7: Moisturize or mist the top of the newspaper at least twice per day.

Step 8: Once white pinheads start to appear, get rid of the newspaper, but continue misting the mushroom daily until they mature and ready for harvest.

Growing Portobello Mushrooms Indoors

Growing Portobello Mushrooms Outdoors

Step 1: To start, ensure that it’s the best season to grow portobello mushrooms. The ideal temperature for them is between 50 and 70 degrees Fahrenheit.

However, you don’t have to wait for the best season to start growing them. If the outdoor environment doesn’t have suitable temperature for growing mushrooms, use a cooling or heating system as needed.

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Step 2: Prepare and set up the growing bed. A raised bed is more advantageous for portobello mushrooms as it is easier to control the soil quality. This type will also warm faster, helping with temperature control, and it’s easier to maintain.

The ideal bed dimension for growing portobello mushrooms is a 4×4 feet bed that is 8 inches high.

Step 3: Fill the growing bed with around 6 inches of compost. You can use cow dung or chicken deposits, two of the best compost manures for growing mushrooms. If you don’t have any of this readily available, purchase a composted manure from stores.

Step 4: Sterilize the growing bed. To do this, cover it with a cardboard box, then with black plastic. Keep the entire bed covered that way up to two weeks.

Step 5: After 2 weeks, remove the covers, and it’s ready for growing mushrooms. Start by sprinkling the spores on the compost manure then mix lightly.

Step 6: After mixing to let the spores settle between the soil and manure, cover the compost with a peat moss layer. Finish it with a layer of newspaper on top to help the growing bed retain moisture.

Step 7: Moisturize the growing bed daily, at least 2 times per day, using distilled water. Continue misting for at least 10 days until white pin heads begin sprouting. It is a sign that the spores are growing and ready for harvest once fully grown.

Growing Portobello Mushrooms Outdoors

Essential Things to Know When You Grow Portobello Mushrooms

Mushroom farming at home is easy and hassle-free with the right growing conditions ideal for growing portobello mushrooms.

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One of the vital things for growing portobello mushrooms is to choose the best soil conditions to promote mushroom growth. Portobello mushrooms grow best in manure composts rich in nutrients.

The ideal substrate for planting mushrooms is horse manure mixed with straw that is well soaked. Portobello mushrooms like its substrate moist, enough for a few droplets of water to come out when you pinch the mixture. Also, make sure that the compost has no worms or something similar that will eat the spores.


It is essential to keep the growing bed moist when you grow portobello mushrooms. They need enough water to grow faster. The ideal watering approach is to mist or moisturize the mushrooms at least twice a day, once in the morning and another at night.

However, make sure that the substrate is damp but not flooded. Using the right kind of water for mushrooms is essential as well. Choose distilled water and avoid anything with chlorine as it can damage the mushrooms.

Light Condition

Portobello mushrooms thrive best in a darkened room. They don’t have chlorophyll and won’t need nutrients from the sun. Put them away from direct sunlight as the mushrooms can develop dark brown caps because of that.

However, at the early stage of growth, as they begin forming heads, portobello mushrooms will require dim light. Indirect sunlight or light from a fluorescent lamp is sufficient at this stage.

Growing Temperature

Portobello mushrooms grow best at a temperature between 50 and 70 degree Fahrenheit. When you grow portobello mushrooms, 60 degree is ideal, and a steady temperature will help with their maturity. Using a thermometer should help with that.

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What Kind of Fertilizer Do Mushrooms Need?

The best fertilizer to use when growing portobello mushrooms is one from the compost manure. They will grow well even without feeding, and many growers opt-out of that.

However, you can also use liquid fertilizer to feed your mushrooms. Conventional fertilizers for mushrooms include horse manure liquid made from combining horse dropping and water, and salt dissolved in water.

Saltpeter is also an excellent fertilizer for portobello mushrooms.

Harvest Time of Portobello Mushrooms

It’s easy to identify if portobello mushrooms are ready for harvest. You can start harvesting them as soon as they reach their ideal size, which is between 4 to 6 inches in diameter.

Portobello mushrooms are easy to grow both indoors and outdoors. They also grow big quickly, and most of the spores you planted will start becoming white pinheads after 10 to 12 days. A week after that, mushrooms will be ready to harvest, 2 to 3 weeks since planting the spores.

Although you planted the spores together, they won’t reach the same size at the same time. Avoid rushing to harvest the mushrooms; instead, wait as they grow into the ideal size. Expect harvesting around three batches in that period before you need to plant another supply of spores.

Also, only harvest firm and whole portobello mushrooms for cooking at home. Avoid using soft, wrinkled, and spoiled mushrooms with noticeable damage from insects and birds.


It’s easy to start a mushroom farm at home as soon as you get portobello mushroom spores on hand. With time and effort, you can grow portobello mushrooms and harvest them to make a homemade feast the entire family can enjoy.

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Jill Sandy

I am a sustainable focus gardener. I love decorating my home backyard with beautiful landscape design and creative garden care techniques I develop myself.