Money Flower

From the Super Mario Wiki

The Money Flower is a flower, that makes money when a Beezley goes into it. As long as the flower isn't in collision with anything, it keeps making more and more money inside it. But if the money is inside the flower too long, the flower dries and there only comes a small coin. The money flower appears in Wario Land 4, and it's located in the level Wildflower Fields.