I have to make cupcakes for a wedding. They will be covered in buttercream and then have fondant flowers and hearts on top. I did a test and the problem is when I put the fondant flowers on and then cover the cupcakes in an airtight container, the flowers literally wilted. My question is how long can cupcakes sit out uncovered without getting stale and dry?

Fondant will wilt and soften if you keep it in an airtight container.

You can make the flowers and hearts few weeks in advance and leave them to dry out in a plastic-wrap covered tray so they don't become soft.

Make the cupcakes as planned, a day before the event and place the decorations on top before delivering. HTH!