To grow a giant pumpkin, add fertilizer and nutrients to the soil, and allow the vine plenty of space to grow. The pumpkin requires protection from wind and other elements until it is well-established.
Start giant pumpkins indoors in early spring, and transplant the seedlings to the garden after the danger of frost has passed and the seedlings have at least five leaves. Prepare the soil by mixing fertilizer, such as rotting cow manure, into the top 4 to 6 inches of soil, and apply lime if it is recommended according to soil tests. Nitrogen, phosphorus and potash are recommended soil additives when growing giant pumpkins, along with a general-use fertilizer.
Plant the pumpkins in hills that are spaced 20 feet apart in a location that receives plenty of sunlight. Seedlings and small vines should be protected from the elements. Use windbreaks until the plant is at least 3 feet long, and shade the plant from direct sunlight on very hot days. Giant pumpkins prefer well-drained soil, and they should be watered frequently.
Hand pollination is typically recommended when growing giant pumpkins. To pollinate by hand, remove a male flower, identifiable by the stamen, and rub the stamen onto a female flower that has a small pumpkin underneath it. Vines should be limited to four pumpkins each for optimum growth, and the vine should be trained to grow away from the pumpkin to prevent damage to the vine.