Why Can’t We Grow Fruit the Size of Cars?

Biologist/mathematician J.B.S. Haldane’s 1926 essay “On Being the Right Size” puts the kibosh on giants. Such legendary behemoths as Gargantua and Pantagruel, Paul Bunyan, and the giant encountered by Jack at the top of the magic beanstalk, explains Haldane, would have all fallen victim to gravity: Their bones, unable to support their weight, would have shattered the minute they took a step.

The point of the Haldane essay is that all species have size limits. Animals, grown too big, can’t function. A hummingbird the size of a turkey, for example, wouldn’t be able to hover; and a grasshopper the size of a pony wouldn’t be able to hop. The Blob of horror sci-fi movie fame—basically a giant amoeboid lump of jelly—would have died of oxygen deprivation before it swelled to the size of a soccer ball.

Plants have their limitations, too. Jack’s beanstalk, for example, is a vine. Unlike shrubs and trees, vines can’t stand upright on their own, but need support. By all biological rights, the beanstalk should have toppled over before it reached Jack’s knees and started to crawl. Even trees can grow only so tall; at something over 400 feet, they find it impossible to pump water all the way from roots to treetop. And vegetables—well, clearly they have to stop somewhere, too, but nobody is quite sure just where.

The Importance of Being the Right Size

Take pumpkins. Pumpkins are Cucurbits—a.k.a. squash—members of the vast and messy Cucurbitaceae family that also includes cucumbers, melons, and gourds.  The pumpkin most of us think of as pumpkin—the fat, orange fruit of jack-o-lanterns and pumpkin pie—is officially a Cucurbita pepo, characterized by a pentagonal prickly stem. Giant pumpkins, however, are another story. Mammoth pumpkins—C. maxima—which have round stems, originated in South America where, then the size of softballs, they were eaten whole by giant ground sloths. Domesticated, the seeds were brought to Europe by the Spaniards, and then eventually bounced back again, eventually reaching the garden of Henry David Thoreau, who planted one and grew a 123.5-pounder that won a prize at the Middlesex Fair in 1857.

Gardeners fell for Thoreau’s pumpkin. In 1900, William Warnock of Goderich, Ontario, using seeds from the same strain, produced a 400-pounder, a pumpkin so mind-bogglingly enormous that he was invited to display it at the Paris World’s Fair. Warnock’s pumpkin remained the undisputed champion of squash for nearly a century—until Howard Dill, of Windsor, Nova Scotia, developed the pumpkin breed now known as Atlantic Giant. Today permutations of Dill’s Atlantic Giant are turning out pumpkins pushing 2,000 pounds.  They’re big, but they’re not pretty. The larger a pumpkin gets, the greater its tendency to slump and spread. You can picture a gigantic Atlantic Giant by imagining Jabba the Hutt as a squash.

According to David Hu and colleagues at the Georgia Institute of Technology, there’s no reason to think the pumpkin is going to stop at a mere two tons. Based on force measurements—in which hapless pumpkins are crushed in vices—the researchers concluded that pumpkins should be able to attain weights of up to 20,000 pounds. That is, enough pumpkin per pumpkin to make 10,000 pumpkin pies.

Giant Vegetables, Every Gardener’s Dream

Many vegetable gardeners have a passion for gargantuan vegetables, and there are annual competitions and prizes for those with the biggest. Among past champions: a beach ball-sized 25-pound potato, a 76-pound cabbage from Alaska, a massive 19-pound carrot, a thigh-sized leek, and an awesome 7-pound, 12-ounce tomato. Most of these were produced with a combination of water, fertilizer, pampering, and luck, though one grower attributes at least part of his veggie success to Glenn Miller records.

Visions of feeding the world with giant vegetables, however, are unlikely to become reality anytime soon—despite a plug from Woody Allen’s 1973 comedy Sleeper. In that film Miles Monroe, the baffled main character, is propelled 200 years into the future, where he encounters a farm propagating tree-sized celery stalks and bananas the size of canoes. The truth is that many prize-winning giants, selected for bulk, not yumminess, simply don’t taste all that great. The trade-off for immensity is flavor, which most of us aren’t willing to give up.

There’s a real advantage, in other words, in being the right size.