Flowertale is an AU created by Neskybo and is a brother AU to Sanei's Flowerfell. In Flowertale, each time monsters die, they grow flowers on their body. Flowertale Frisk's personality is experimental, and they reset the game to satisfy their curiosity. The flowers that grow are a result of the corruption of the timeline due to the resetting. How flowers appear on the body of a monster is dependent on the rate of their dusting. As an example, someone who is beheaded receives flowers on their neck. Undyne receives flowers all over her because she melts.
Each monster grows a different flower that represents them. Sans' flowers are Meadow Saffron, symbolizing that their happiest days are in the past. Asriel's flowers are Star of Bethlehem, which represents atonement.