How to Care for Portabella Mushrooms

Provide your mushrooms with a stable and consistent temperature -- 65 to 70 degrees Fahrenheit is an ideal temperature range for portabella mushrooms and produces the best growth results. Keep the mushrooms in a room or environment where this temperature is easily maintained or you run a risk of ruining your crop.

Keep your mushrooms moist. Your portabellas require a heavy layer of moist peat moss, newspapers covering them and a moist compost growing medium when they're still spores before they even develop into mushrooms. Once developed into tiny pinprick mushrooms and until they are harvested, portabellas require once or twice daily misting with non-chlorinated water. They must also be kept in a humid, moisture-conserving environment such as a ventilated mushroom tent.

Grow your mushrooms in well-rotted compost as a growing medium. This provides the portabellas with plenty of nutrients they need to grow big and healthy, as well as to keep producing more mushrooms. The portabellas eventually stop growing in your mushroom garden once the nutrients run out. Provide a well-nourished base to begin with.

Keep your mushrooms well-ventilated in their growing environment to prevent a build-up of carbon dioxide. Carbon dioxide build-up around your portabellas is toxic to them and prevents them from growing or producing more mushrooms. A mushroom tent or even plastic bag with holes punched in it used, provides plenty of ventilation for the portabellas.