How to grow a giant pumpkin, with help from science

WAPPINGERS FALLS, N.Y. (AP) — The pumpkin in Tony Scott's backyard weighs almost as much as a small car.

He's been tending to it for months, feeding it fertilizer and covering it with a blanket at night to keep it at a stable temperature. A roll of measuring tape wrapped around the pumpkin gives him a rough estimate of its size.

“I've never seen anything grow this fast,” said Scott, a semiconductor engineer from upstate New York.

Every year, growers like Scott push their pumpkins to the limit. They compete in annual weigh-offs with colossal fruits that are well over 2,000 pounds (900 kilograms). Scott's pumpkin took third place this year, coming in at 1,931 pounds (876 kilograms).

Pumpkins aren't the only crops that can get giant. Other members of the gourd family like squashes, cucumbers and watermelons are capable of a similar feat. But the orange behemoths are especially massive and have earned a place of honor at fall festivals and Halloween fairs.

How to grow a giant pumpkin

A giant pumpkin starts off as the perfect seed. Growers choose seeds that have yielded large pumpkins in the past or test new ones. Scott and many other growers rely on the tried-and-true Atlantic Giant pumpkin seeds.

After that, it comes down to the right combination of water, nutrients and care.

Giant pumpkins can guzzle hundreds of gallons of water in a day and make their own food from sunlight just like regular-sized plants do. Their internal plumbing system is more robust, allowing them to drink up sugary water and nutrients faster.

As the leafy patch begins to expand, growers remove smaller pumpkins so all the water and nutrients funnel into a single fruit.

“That helps make it extra big in a way that you might not see in the wild," said Aleca Borsuk, a plant scientist at the New York Botanical Garden.

Because of gravity, giant pumpkins grow wide but not tall. They often resemble lopsided, lumpy pancakes. Scott's pumpkin is also lighter in color because he covers it with a tarp during the day, protecting it from sunlight which can ripen and harden the skin. He waters it using an overhead sprinkler system.

Can giant pumpkins grow forever?

“The answer is no,” Borsuk said. No matter how big a pumpkin gets, it'll eventually mature and its natural aging cycle will kick in.

Scott has nurtured giant pumpkins for eight years. It still blows his mind watching them inflate, putting on around 40 pounds to 50 pounds (18 kilograms to 23 kilograms) a day. He sets up reflective panels and even a fake wolf cutout to ward off hungry deer and other intruders looking for an orange-colored snack. Woodchucks have nibbled on the pumpkin's vines in previous years.

After the all-important weighing competition, Scott shows off the giant pumpkin at various themed events and drives it around on a trailer. Eventually, he donates it to be displayed or carved.

On the way to events, he often gets stopped by people who ask what he's got in the back.

“The first question they ask is, ‘Is it real?’” Scott said. “Where would you buy a fake pumpkin this big?”

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.