Pack the peat pot with seed-starting soil roughly two weeks before the last frost date in your area. Set a seed 1 inch deep into the pot, and water it well.
Test your garden soil. Incorporate compost or other amendments at least 1 foot deep into the dirt, using the test results as a guide. Err on the side of too much compost rather than too little, since pumpkins are very heavy feeders.
Transplant the seedlings after the last frost date. Give each pumpkin vine at least 150 square feet -- the more foliage, the more food for the growing pumpkin. Keep the soil evenly moist, but not wet. Pumpkins require large amounts of water.
Watch for the first fruits at the base of female flowers. If you wish to have one extremely large pumpkin, leave only three pollinated flowers per vine. Wait until the three pumpkins reach roughly 6 inches in girth, then remove the two smallest.
Monitor the stems of these fast-growing giants. Dill's Atlantic Giant pumpkins, because of their growth rate and size, often kink or pull away from their stems. When the pumpkin is young, move excess vine into an S-shape near the pumpkin to ensure each vine is long enough for future growth.