Start the planting process in late May or early June. Big pumpkins need three or four months where the daytime temperatures exceed 75 F.
Dig your planting area with a spade to a depth of about 1 foot. Mix fertilizer or compost in with the dirt. Moisten the soil, then plant a group of two or three seeds 1 inch apart. Put a 1/2-inch of moist soil over the top of the seeds and pack it down gently. Cover the area with another 1/2-inch of loose soil.
Keep the ground moist as the plants grow, but avoid over-saturating the ground with water. When the plants develop three leaves, examine them closely. Remove the two weaker plants, leaving the strongest one in the soil. Pull any weeds that appear in your planting area.
Monitor your plant as it grows. When three fruits have set, pinch the vines back so they're perpendicular to the pumpkins. Once your trio of pumpkins grow to a diameter of 6 inches, choose the one with the best shape and remove the others. Pick any additional blooms that appear on the vine.
Adjust the pumpkin's position each week with a gentle roll. Place cardboard or wood beneath it to help fight insects. Provide nitrogen to your pumpkin by adding manure or compost to the soil every two weeks.
Remove your pumpkin from the vine before the first frost of the year. When the stem develops a hard, wooden quality, cut it with a sharp knife two inches from the top of the pumpkin.