Some varieties of pumpkins have the ability to get larger than others, so it is important to grow a pumpkin from good seeds of the right variety. Fertilizing pumpkins is also important if a large size is desired.
Pumpkins should be grown in a good mix of soil that includes up to 4 inches of cow manure if a natural fertilizer is wanted. Vegetable fertilizers designed for maximum growth also work well.
Consistent watering is essential to growing a big pumpkin. A drip irrigation system can be used to provide a steady amount of water during the entire growth cycle of the pumpkin. As the pumpkin grows, it will need to be turned or set upright so it does not grow in an odd shape.