Here is the full list of all 14 Pumpkins achievements.
Rank a blue ribbon on all levels.
Rank a green ribbon on all levels.
Recover every pumpkin in the game.
Win a blue ribbon in the Snail Races.
Win a Green Ribbon on "Stack the Pumpkins!"
Rank a blue ribbon in the Slime Pond.
Beat the game!
Find one of the hidden pumpkin patches!
Clear the level "Margins"
Clear the Level "A Turkey Parade"
Clear the Level "Haunted Maze"