To grow a giant pumpkin, you will need to select a pumpkin variety with the potential to grow to a large size. This variety regularly tops 200 pounds, says Nichol's seed catalog. Plant your pumpkin seeds after the danger of frost has passed and the soil is thoroughly warm. Or start your seeds indoors and transplant outside when the soil warms up above 55 degrees. Check on the seed packet the number of days recommended for the pumpkin to grow big.
Pumpkins love fertile soil.
Before planting, Penhallegon recommends spading the soil about a foot deep and mixing in some compost, manure, or well-balanced fertilizer. Then plant two or three seeds in a group about an inch apart in moist soil. Keep the soil moist, but not wet. Too much water will slow plant growth and encourage fungus diseases. Once your pumpkin seedlings have three leaves, remove all but the strongest plant.