Growing mammoth pumpkins starts with choosing seeds famed for growing the hardiest and largest orange monsters. Help these giant pumpkins on their way to greatness by tilling the soil deeply and adding plenty of aged manure or other nitrogen-rich fertilizer, protecting the pumpkins on cold nights and growing one or just a few pumpkins per vine. Jumbo pumpkins need at least 120 days growing time and most have thick, orange skins.
Developed by pumpkin expert Howard Dill, Atlantic Giant potentially grows to astonishing girth. In 2009, one Ohio grower achieved a record-breaking 1,725 lbs. with an Atlantic Giant. This variety is more prone to cracks, uneven or pale color and flat spots than some other varieties, so determined growers need to be extra vigilant when undertaking this "high risk, high reward" pumpkin.
The University of Illinois Extension Service calls the Prizewinner hybrid one of the more dependable of the "jumbo" pumpkin types, although it doesn't reach the record size of Atlantic Giant. Its shape and color is also listed as "superior" to Atlantic Giant. On average, the pumpkin grows from 50 to 200 lbs.
Big Max represents a good choice for both exhibitions and pie making. The University of Illinois finds an average size of 30 to 50 lbs. for Big Max growers, although Burpee promises its version reaches 100 lbs. The variety's skin color is bright orange, while the flesh is bright yellow and smooth. Three Southern region extension services--Clemson in South Carolina, Texas A&M and the University of Florida--recommend Big Max as a pumpkin suited for Southern gardens. Its flesh is 3 to 4 inches thick, making it a good candidate for storage.
Capable of reaching 200 lbs. with enough care, Big Moon boasts dark orange skin. Big Moon greatly resembles Big Max in terms of suitability for Southern gardeners and its potentially massive size. The University of Virginia Extension Service further recommends Big Moon as a disease-resistant variety for those gardeners who have combated powdery mildew on their squash varieties in the past.