Pumpkin magic is a form of magic possessed by Cinderellas. It is a reference to the spell that changed the original Cinderella's pumpkin into a coach.
Pumpkin magic is a form of magic Cinderellas possess and can use as long as they have a wand. The source of this magic is the Cinderella family dragon. Cinderella implied that she was taught this magic by her Fairy Godmother.
Pumpkin magic can summon pumpkins out of thin air. A user of this magic can summon these small pumpkins wherever they are. However, there is a limit to the size of the pumpkin they can summon. No one, not even the Cinderella Dragon herself can summon a giant pumpkin.
The main use of pumpkin magic is transforming pumpkins into something useful. Rose uses this countless times to turn pumpkins into vehicles like scooters, roller skates, cars, coaches, etc. In "Pumpkins and Dragons", it is revealed that the whole school was conjured from a colossal pumpkin. Strong users can change pumpkins into buildings but it takes a giant pumpkin and a powerful user or more to conjure a building as large as Regal Academy.
Like the coach, the spells have limits. Some revert to pumpkins at midnight while some disappear after a few minutes or hours. The spell that summoned the school lasts for years but it must be renewed every know and again or the spell will be broken.
A big disadvantage of magic pumpkins is that when they die, they either wilt, wither and collapse or explode or both.