This is a pic of one of our Atlantic Giant pumpkins. According to giant pumpkin grower, Howard Dill, the trick to getting a big pumpkin is to only allow 1 or 2 blossoms to mature into fruit and to make sure the fruit is "set" by early July. This means you have to decide early on which pumpkins look the healthiest and most promising as far as size and shape goes. Then, you will have to continually cut any new blossoms off. Another thing to consider when growing the giant pumpkins is fertilizer. Early in the season, it's best to provide the plants with a water soluble fertilizer that stresses phosphorus such as a 15-30-15 mix. Once the fruit sets you should switch to a balanced blend such as 20-20-20. Then in late July switch to a fertilizer that is heavy in potassium like a 15-11-29. Some competitive growers fertilize at a rate of 1 to 2 lbs per week from the time the fruit sets to the end of the growing season. We didn't go that crazy with the fertilizer this year but perhaps next year we will be a little more aggressive with it. Trimming vines is also a crucial to growing these giants. You should start pruning early in the season. Essentially, what you want to prune are the main vines once they reach 10 to 12 feet beyond the set fruit. The side shoots off the main vines should not be longer that 8 feet and apparently burying the cut ends of the vines helps to prevent water loss.
Last year we had a couple decent size pumpkins but we hope to surpass that this year....we still have a month to go, so it looks promising.
On another pumpkin note, we grew about 10 sugar pie pumpkin plants this year. They are just starting to turn orange and I can't wait to try cooking with them. Last year we adapted our own pumpkin pie recipe from this site's recipe and it was fabulous:
http://www.pickyourown.org/pumpkinpie.php
I want to try new pumpkin recipes so I would love to hear from anyone that has a great recipe to share.