The Pumpkin is a plant that can grow in any grassy areas throughout the surface world during Halloween and can be harvested with a Pickaxe. They can be used to craft various items, including food, Jack 'O Lanterns and Furniture.
Outside of the Halloween Season, Pumpkins can be grown with Pumpkin Seeds, which can be bought from the Dryad for 2 50 .
If you find it difficult to find many pumpkins, you can consider building a farm. A farm consist of parallel, horizontal layers of dirt with grass, each pumpkin 3 blocks apart from the next. Because of the simplicity of building such farm, it is recommended to create a farm rather than to go searching for naturally growing pumpkins. However, pumpkins only spawn during the Halloween season. They must be planted otherwise.