If you break a block with a plant pot on top of it, it will duplicate the flower inside the plant pot.
From the pictures -
Picture 1 - Plant in plant pot on top of slab
Picture 2 - After breaking the sandstone slab
Picture 3 - 2 Birch tree saplings in inventory from the drop
Duplicate of MC-30537 - If you have not, please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.