How do you get mushrooms on backyard monster?

Answer 1

Mushrooms aren't "bought". They will just grow on your plot of ground (not necessarily always inside the boundaries, though). Click on it and select the "Pick" button to make one of your workers (the tiny blue ball monsters) to pick it. You do not necessarily "get" mushrooms. Some mushrooms have prizes in them, like shiny (money that you usually can only get with real money)! However, a lot of them are duds, and cannot be used for anything else. They aren't a resource or anything. I always start my game of Backyard Monster by picking all of the mushrooms I see and trying my luck if most of them are mushrooms containing shiny. I suggest concentrating on building and attacking rather than worrying about picking the mushrooms though; they won't do anything negative to you.

Answer 2

All you can really do is wait. Mushrooms grow daily, so come back and check every day!