Biological secret that makes pumpkins swell up to the size of cars, while blueberries stay tiny

Although they are both fruits, pumpkins can weigh more than a ton, while blueberries only weigh a few dozen grams. Scientists have found the surprising biological reason behind it.

Pumpkins possess unique biological characteristics, including the ability to grow indefinitely with an elastic shell and a “super-fast” vascular system, making them “giants” of the plant world - Photo: Wiktor Dabkowski/dpa/Corbis

Every autumn, giant pumpkins weighing more than a ton appear, surprising people, while the world's largest blueberry weighs less than 30 grams. Why is it that one fruit can swell to a record size, while the other remains tiny?

According to plant scientists , pumpkins (which are a member of the gourd family) possess rare biological characteristics that allow them to grow to "giant" sizes, something that other fruits, such as apples or blueberries, cannot do.

Giant pumpkins from the Cucurbita maxima genus, often called the "Atlantic Giant" or "Mammoth" strains, have been bred over generations to increase in size. The key is that they are "indeterminate" plants, meaning they have no natural growth limit. While many determinate plants stop growing once they reach a certain size, pumpkins just keep growing, if conditions allow.

"When a plant needs more energy to grow fruit, it just grows more leaves and stems. There's no 'genetic bottleneck' that forces it to stop," explains Vikram Baliga, an agronomist at Texas Tech University.

Pumpkins selected for competition are often given special care - Photo: Shelby Lum

According to Live Science, giant pumpkin growers often remove all the other fruits, leaving only one on the vine. At that time, all the nutrients the plant absorbs are concentrated on the "only child", causing it to swell at an unbelievable rate, possibly gaining up to 20kg per day during the peak period.

In theory, this method can also be applied to other fruits such as peaches or apples, but if they gain too much weight, they will fall off the branch due to gravity. Pumpkins are different, they stay on the ground so there is no fear of falling or breaking.

Another advantage of pumpkins is that their shells are hard but flexible, allowing them to expand without cracking. If the shell is too soft, the fruit will collapse under its own weight; if it is too hard, it will crack as it grows. Growers must adjust sunlight, temperature, and humidity to keep the shells “flexible” enough to allow for swelling.

Biologist Jessica Savage of the University of Minnesota Duluth says the giant pumpkin also has a “superpowerful” vascular system, with more phloem tissue than regular squash. This helps transport sugars and nutrients to the fruit more quickly, like opening up more “highway lanes” for energy flow.

Despite their biological advantages, giant pumpkins are the result of centuries of selective breeding, where humans only kept individuals with the potential to grow larger. Unlike fruits that are selected for sweetness or color, giant pumpkins are "bred" purely for size.

As a result, every fall, "orange giants" appear at American agricultural fairs, where a pumpkin can weigh more than a small car.

Experts believe the limits of pumpkins are still far from being reached. “Maybe one day we’ll see a pumpkin that weighs 2 tons,” says Professor Savage. “People are still trying to make them bigger.”

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MINH HAI

Source: https://tuoitre.vn/bi-mat-sinh-hoc-khien-bi-ngo-phinh-to-nhu-o-to-con-viet-quat-nho-xiu-20251028100016145.htm