Big pumpkin varieties, sometimes called giant pumpkins, can reach hundreds of pounds in size. Not all pumpkins have the ability to get so big. Certain varieties, such as Prizewinner and Big Max, regularly reach sizes larger than the average pumpkin. In order to succeed at growing big pumpkins, proper care must be taken throughout the growing season. Because pumpkins require a long, warm growing season, starting the seeds indoors gives them the time they need to reach maturity and to reach an epic size.
Fill 12-inch diameter peat pots with a moist, quality seed starting soil. Peat pots are planted directly in the garden, limiting damage to the roots at transplant.
Sow two pumpkin seeds in each pot, to a depth of 1-1/2 inches. Mist the top of the soil with water to moisten it, then cover it with a layer of plastic wrap.
Place the pots in a warm room to germinate, which takes approximately seven days. Remove the plastic once germination occurs, and move the plants to a warm, sunny window.
Remove the weaker plant from the pot if both seeds germinate. Snip the plant off at the soil level with clean scissors once the plants are 1 to 2 inches high.
Prepare a full-sun, well-drained garden bed for planting after frost danger is past and once the seedlings have produced their first large leaf. Apply a balanced fertilizer to the bed, following label application instructions, three days before transplanting. Work the fertilizer into the top 6 inches of soil.
Dig planting holes 1/2 inch deeper than the peat pot and twice as wide. Tear off the top rim of the pot and set the whole plant, pot and all, in the hole. Fill in around the pot with soil, applying an extra 1/2 inch of soil on top of the pot. Plant one giant pumpkin plant per 2,500 square feet of garden.
Water pumpkins immediately after planting to moisten the soil. Water the plants once a week during the morning, providing 1 inch of water. Water more frequently to prevent the soil from drying out during extended dry periods.
Fertilize with a foliar spray made for pumpkins once the plant begins setting fruit. Follow label application instructions.
Harvest all but the healthiest and largest pumpkin from each plant once the pumpkins reach the size of a volleyball. Cut these pumpkins off cleanly, 3 to 5 inches up the stem. This allows all nutrients to go to the one pumpkin, making it more likely to produce a big pumpkin.
Clip off any roots that form along the vine more than 3 feet out from the main plant, allowing the vine to lift into the air as the pumpkin grows. Straighten out any kinks in the vine while the pumpkin is still small and easy to move.
Harvest the pumpkin once the rind is hard and the vines are beginning to yellow and die.