How to grow a 2560 lb pumpkin

In early October, Travis Geinger hauled a huge white-and-orange pumpkin monster out of his home in Minnesota for a championship in Half Moon Bay, California. There, Ginger was crowned the winner – and his pumpkin, named ‘Maverick’, set the record for the largest ever grown in North America. It weighed 2,560 pounds and earned him a total of $23,040, at $9 per pound.

Gienger’s Maverick is part of a trend in award-winning pumpkins that are getting bigger and bigger. In 1900, the heaviest pumpkin on record weighed 400 pounds. The first to exceed 1,000 pounds was introduced in 1996, and the 2,000-pound mark was passed in 2012. Now, 3,000 pounds doesn’t seem too out of reach: the current world record belongs to an Italian grower who produced a 2,702-pound pumpkin in 2021 Mr.

How do competitive growers get their pumpkins to swell to enormous sizes? And what is unique about pumpkins—compared to other crops—that allows for such growth? Biology has the answers.

Geinger, who teaches horticulture at Anoka Technical College, says he starts growing his pumpkins in mid-April, starting with seeds he grows indoors for the first few weeks when Minnesota soil is too frosty. Once it warms up, Gienger moves the plants outside, where they can absorb sunlight, nutrients from the soil and water — lots of water. “At the peak, you’re watering maybe 150 gallons, 200 gallons a day,” he says, and that’s on a pumpkin. Fruits are about 90 percent water, so it’s no surprise that water is a crucial ingredient for massive growth.

Depending on the variety, pumpkin plants can grow up to a dozen fruits per vine. But to maximize size, growers remove all but one or two of those pumpkins to reduce competition for resources, says University of Georgia horticulturist Robert Westerfield. (Gienger, for example, grows only one pumpkin per plant.) For the same reason—competition for limited resources—growers also remove all weeds in the area, Westerfield adds.

But what exactly happens inside the pumpkin as it grows? “Ultimately, the size of any organ—in this case, a pumpkin fruit—is determined by the number of cells and the size of the cells,” says Rebecca Grumet, a plant biologist at Michigan State University. In other words, two factors drive natural growth: cell division and cell expansion.

Cell division accounts for most of the growth early in a fetus’s life, Grumet says. This period of cell division lasts about 20 days in pumpkin plants. By comparison, the period is only four to five days for cucumber fruits, which are also part of the gourd family but don’t grow as large, she says.

Once cell division stops, cell expansion is responsible for continued growth, Grumet says. Cucumber cells will expand until about 20 days after pollination. In pumpkins, however, that number is more like 50 or 60 days, which allows pumpkins to develop larger cells than other fruits, she explains.

Champion growers aim to extend the pumpkin’s natural growth period as long as possible. Gienger says his 2,560-pound pumpkin continued to grow for about 120 days, including both the splitting and expansion phases — although there was only a small increase day-to-day at the end of that period. The pumpkin probably could have gotten even bigger, Ginger says, but he had to harvest it in time for the weigh-in in California. Plus, growing a pumpkin too long runs the risk of it splitting.

Fruit growth is also determined by how much sugar is transported to it, as opposed to other plant structures such as leaves, stems, and roots. Internal vesicles called phloem carry sugar to the fruit, and research shows that pumpkins have more specialized phloem tissue than most plants, which helps them grow even bigger. And giant pumpkins seem to have even more phloem tissue than smaller pumpkin varieties, Grumet adds.

Also, hormones can play a key role in growth, says Courtney Hollander, a plant biologist also at Michigan State University. In particular, gibberellic acid or GA, a natural hormone, stimulates both cell growth and cell elongation. Naturally higher levels of GA can cause fruit to grow unexpectedly large, Hollander says, and farmers who treat their crops with GA sprays can expect to see larger ones. (Such sprays are allowed in pumpkin-growing competitions, Gienger says, but he notes that his own process does not use GA.)

Genetics also affect pumpkin growth. There is a wide variety of pumpkins, and some will never get large, while others are bred specifically to maximize their size, Westerfield says. (Some very large pumpkin varieties have names like Prizewinner and Big Moose.) But the variety most competitive growers prefer today is called Atlantic Giant. It was created by a Canadian pumpkin breeder named Howard Dill in the 1970s. Gienger’s North American record holder was the Atlantic Giant.

Still, there is genetic variation even among pumpkins of the same variety, Westerfield says. Some Atlantic Giant seeds are more ready to grow than others. This variability has caused competing pumpkin growers to place a high value on the best seeds. After each harvest, many growers auction off the seeds from their largest pumpkins to plant the following year, Ginger says.

Gienger grew a 2,350-pound pumpkin a few years ago and sells individual seeds from it for $175 each. He says he will also auction the seeds from his new winner. But he’s not sure if he’ll use those seeds in his own crop next year.

“I don’t usually grow my own seeds,” says Ginger. He prefers to explore the market for seeds with the greatest growth potential. Ideal candidates, he says, are those from a pumpkin that has grown to enormous size in a novice grower. Because the grower was new to the game, the growth of their pumpkin probably had more to do with good genetics than ideal farming practices, Ginger says.

Is there a limit to how big pumpkins can grow? “I don’t know the answer to that, and I don’t think anyone does,” Geinger says. “I’d say in my lifetime we might see £4,000.”

Hollander says research shows there’s a limit to how big cells can grow, so there must be an upper limit to how big pumpkins can get in the future. “What that limit is, I really don’t know,” she says, “but you’ll never get a pumpkin as big as a house.”

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