Growing your own gourmet mushrooms is a fun and rewarding family activity. With this easy-to-use kit, you can start harvesting mini portabellas (also known as crimini mushrooms) in three to five weeks, or let them continue to grow and they'll reach 3" to 5" across. You'll get several crops over an 8- to 12-week period. The first two or three crops are large, often filling the box with mushrooms; subsequent crops get smaller until the mushrooms finally stop. Please start growing within 2 weeks of arrival.