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Have you ever brought home a massive watermelon, only to have it explode all over your kitchen? It's a rare event, but once it happens, you’ll never again look at a watermelon without wondering about its potential for mayhem. Kypros/Getty ImagesNothing quite symbolizes the arrival of summer like a vibrant, ripe watermelon. That is, unless your sweet, refreshing treat suddenly starts spitting, hissing, foaming, and then erupts with a loud KABLOOEY, showering spoiled juices across your picnic or—heaven forbid—drenching your kitchen or beautifully set table with mushy melon innards.
So, just how infuriating can a single fruit be, you wonder?
For the most part, you’ll encounter no friendlier snack than a watermelon. It’s the John Candy or Labrador retriever of the fruit world. But occasionally, like with anything in life, you may stumble upon a bad one. When that happens, don’t panic or turn your back on the humble Citrullus lanatus. Instead, embrace the curiosity and marvel, as a watermelon explosion certainly makes for a fascinating science story to share with friends or, better yet, a mind-blowing YouTube moment:
So what exactly happens when a watermelon decides to play the prankster and bursts open?
Walter Reeves Shares His Thoughts
Southeast’s gardening expert, Walter Reeves, aka The Georgia Gardener, explains in an email that the cause lies in the process of fermentation.
"The reason this happens is that the watermelon is packed with sugar, and a rapidly multiplying bacteria or fungus got inside it. It’s fermenting. Maybe it got punctured on its way home, or it could have been infected with a subtle blotch disease," he says.
"Fermentation leads to the creation of various chemicals. Some emit the scent of alcohol, others of vinegar, while some may even smell floral, and so on. As fermentation progresses, it produces carbon dioxide gas, which escapes from the rind with a hiss under even slight pressure. In simple terms, a watermelon can ferment from within, and the buildup of pressure can trigger different reactions," explains the retired radio and TV host, author, and weekly gardening columnist for the Atlanta Journal-Constitution.
Imagine the fizzing sound of a soda can when it’s shaken before being opened.
A bacterial infection can also be the culprit behind a watermelon splitting open.
"Bacterial blotch disease originates from infected seeds and affects only the rind," says Reeves. "It doesn’t penetrate the flesh. However, if the blotch cracks, bacteria and fungi can enter through the cracks and start the fermentation process inside the fruit. If you find a watermelon with a small blotch on its rind, the interior should be safe. But if the inside smells foul or appears watery, it's best to avoid eating it."
Watermelons consist of more than 90 percent water. So, what happens when a watermelon explodes?
"It releases fluid with force," says Reeves. Picture a mini volcanic eruption.
"The explosion," says Reeves, "can be triggered by genetic traits that affect rind thickness, sugary pulp, and smaller fruit size. Thin rind + super-sweet pulp (which soaks up water easily) = BOOM! on a hot day."
The Exploding Watermelon Gene
So, is there really an "exploding gene"?
The splitting or "exploding" of watermelons can also be due to the explosive rind gene found in many heirloom varieties. Dr. Penelope Perkins-Veazie, a plant physiologist and professor of horticulture at North Carolina State University (NCSU), notes in an email that the explosive rind gene was discovered in 1937. Essentially, it makes the rind burst or split when the fruit is cut open.
"A small jolt will crack the rind open, and the pressure inside the fruit forces the flesh to spill out," says Perkins-Veazie. "Triploid (seedless) watermelons need diploid (seeded) pollinators, but typically, growers don’t want to harvest large seeded watermelons. By adding the explosive rind gene to the small-seeded pollinator fruit, it means they can be squished or destroyed, but since they’re usually palm-sized, they won’t make a mess all over the seedless ones."
Mark Twain once declared the watermelon to be "the finest of this world's indulgences, crowned by divine grace as the king of all fruits. Once you’ve tasted it, you’ll know what angels eat."
Mark Twain clearly never encountered the "ooey-gooey, slimy, yucky puddle of crapola" that Walter Reeves describes as the aftermath of a disastrous watermelon rind rupture. Had he, Twain's words might’ve started with, "What in tarnation?" and ended with, "angel vomit."
With the ongoing uncertainty surrounding the coronavirus pandemic, farmers in Florida, the leading watermelon producer in the U.S., worry they could suffer substantial losses on their 2020 crop.
