After Reform and Opening, private enterprises sprang up like mushrooms.
Tips
history
From Zhang Lei's 《食笋》 poem (Song): 荒林春雨足,新笋迸龙雏 — in a wild grove after ample spring rain, new shoots burst forth like dragon hatchlings. The image of rapid proliferation stuck.
usage
Almost always positive — stresses healthy, vigorous growth. Common pattern: noun + 如/像 + 雨后春笋 + 般 + 出现/涌现. The English equivalent is closer to 'sprouting up like mushrooms'.