Larger pumpkin species (Cucurbita maxima) need regular watering and proper fertilization to produce a giant fruit. If bigger is better in your book, you might also thin the fruit to one or two pumpkins.
Even though it’s too late to start growing your own jack-o’-lantern for this year’s Halloween celebration, you can begin strategizing now for how to wow your neighbors next year with giant pumpkins.
Gardeners wanting to grow pumpkins that are big need to start with genetics, says Bob Westerfield, home vegetable specialist with the University of Georgia Cooperative Exension. You’re not looking for the same seed that produces your run-of-the-mill jack-o’-lanterns or pie pumpkins.
The typical pie pumpkin’s scientific name is Cucurbita pepo. The larger pumpkin species is Cucurbita maxima, and these are the seeds you want to start with if your goal is to grow big. Competition pumpkin growers sell the seeds from the previous championship plants for as much as $10 to $20 per seed, says George Boyhan, a UGA horticulturalist who has spent many years breeding standard pumpkin varieties that thrive in the Southeast, but common giant pumpkin seeds are available for less. One of the best-known common giant pumpkin varieties is Dill’s Atlantic Giant, and its seeds start at about $3 per pack.
Once you’ve got the right seed, hold onto it until spring, when you’ll put it into the ground. Pumpkins need to be planted between May 15 and July 1 to reach their maximum sizes by the fall. Giant pumpkins need super-rich, heavily composted soil to thrive. Test and amend your soil until the pH level is at about 6.5 to 6.8. If you’re looking to grow a giant pumpkin, you need to put extra effort into making sure it’s watered regularly and properly fertilized throughout the growing season.
Westerfield warns not to over-fertilize at the beginning because that could stimulate the plant to expend all of its energy growing a super-long or super-thick vine before it produces any fruit. He suggests fertilizing the plant right after planting, once right after the tiny pumpkins appear and maybe twice again before the end of the growing season. You might also want to take precautions, such as using row covers, to control squash vine borers, which lay their eggs inside the vine of the plant and can quickly cause irreversible damage.
Once the pumpkin plant produces flowers, thin some of the female flowers from the vine. The female blooms have tiny fruits at the base of the bud.
After the pumpkins emerge and before they get very large, thin the fruit, as well, so all of the plant’s energy is directed toward making one or two giant fruit. Select one or two of the most promising-looking pumpkins on your plant to keep and pick off the others. Serious championship growers leave only one pumpkin on each vine, Boyhan says, though Westerfield suggests leaving two per vine to double your chances of getting a show-worthy pumpkin.
Once you’ve picked your winners, watch, water and wait. Your pumpkin might need to be rolled around from time to time to keep it from getting soft spots. Some growers like to lay down a bed of hay for their prize pumpkins or keep them on a pallet to reduce the chances of rot.
When late September hits, you should be able to wow your friends and neighbors with what you’ve grown.