Minecraft wiki entry for Pumpkin, associated text: Pumpkins naturally generate with the terrain in most biomes in the Overworld, in the form of random patches. They require only grass blocks with air above (clear of any plants such as flowers or grass), and can generate whether or not that grass block has a layer of snow cover. Practically speaking, this means that the occurrence of pumpkins in stony or sandy biomes, or in grassy biomes with few clear grass blocks, is comparatively rare. Each chunk has a 1⁄32 chance to generate a pumpkin patch, making naturally-generated pumpkins rarer than diamond ore.