treat (one) like a mushroom

informal To keep one uninformed and tell them lies about something. Mushrooms commonly grow in dark environments and feed on manure, so the phrase puns on the idea of being kept in the dark (left uninformed) and fed bullshit (lies). Does your boss tell you the truth anything that's going on? When I worked there, they treated me like a mushroom—that's why I left!

treated like a mushroom

informal Having been uninformed and told lies about something. Mushrooms commonly grow in dark environments and feed on manure, so the phrase puns on the idea of being kept in the dark (left uninformed) and fed bullshit (lies). Does your boss tell you the truth anything that's going on? When I worked there, I was treated like a mushroom—that's why I left!