What Is the Harvest Season for Portabella Mushrooms?

Grown-up Mushrooms

• Portabella mushrooms are mature crimini mushrooms that have been allowed to grow three to seven days longer. Crimini mushrooms are picked before the bottom of the cap opens; portabella mushrooms are picked when the bottom opens to reveal the gills. The light tan, rounded caps of portabella mushrooms can be up to 6 inches across and are slightly rough.

Compost Culture

• Other species of cultivated mushrooms grow on and break down woody material to get nutrients for growth. Portabella mushrooms cannot break down raw materials for their nutrients and grow in broken down material called compost. Mushroom growers use specially formulated compost that usually contains wheat straw and horse manure, and may contain cocoa seed hulls, corncobs, cottonseed hulls, dried brewers grain, gypsum or poultry manure. Spores are collected from mature portabella mushrooms in a laboratory and inoculated into grains or seeds to make spawn, which is mixed into the compost to propagate more mushrooms.

Pins To Mushrooms

• In two to three weeks, mycelium -- a lacy network of roots -- begins to grow in the compost. The growers spread a casing layer of peat moss and limestone over the compost to encourage the roots to form mushrooms. Soon tiny white growths called pins emerge and continue growing into mature portabella mushrooms.

Flushes of 'Shrooms

• Portabella mushrooms grow in flushes or breaks -- cycles of three to five days. The first mushrooms are ready to harvest 17 to 25 days after the casing layer is spread. Each flush produces fewer mushrooms than the last flush, but the grower can usually continue to harvest mushrooms for 30 to 40 days.

A Meaty Substitute

• Fresh portabella mushrooms are light colored with curved, textured caps and uneven edges. They have a rich, meaty flavor and texture. As the mushrooms age, the caps turn dark and flatten out. Firm aged portabella mushrooms have an intense, meatier taste than fresher ones. Store mushrooms in paper bags or wrapped in paper towels in the refrigerator. Use cheesecloth or a small paintbrush to remove any dirt before eating or cooking them. If washing is necessary, use as little water as possible since mushrooms absorb water and become mushy. Portabella mushrooms are good broiled, grilled, roasted, sautéed and microwaved. They are a good substitute for meat, as a main course or in recipes. Raw mushrooms do not freeze well, but cooked mushrooms can be kept in the freezer for several months.