Scientists Solve the Mystery of the Squirting Cucumber’s Explosive Seed Dispersal

For centuries, the squirting cucumber has fascinated naturalists with its explosive method of seed dispersal. This peculiar plant, scientifically known as Ecballium elaterium, ejects its seeds at astonishing speeds, with some traveling up to 33 feet (10 meters). Researchers have finally uncovered the mechanics behind this rapid and ballistic seed release, solving a mystery that dates back to Ancient Rome.

The squirting cucumber, when ripe, measures about 1.6 inches (4 centimeters) long and, upon falling from its stem, launches seeds at speeds of around 45 miles per hour (20 meters per second). The eruption lasts only 30 milliseconds, making it a truly remarkable phenomenon. Though the plant is found in regions across the Mediterranean, northern Africa, and parts of North America, its seed propulsion is unlike that of any other member of the gourd family.

Pliny the Elder, the Roman naturalist, was the first to document the cucumber’s explosive seed release, noting the potential danger it posed to eyes. In the 19th century, scientists suspected that high internal pressure played a role in the eruption, but the specific mechanisms were not well understood—until now.

Using high-speed video, CT scans, time-lapse photography, and 3D modeling, researchers have identified that the squirting mechanism involves more than just a buildup of fluid pressure. The process is shaped by a combination of factors, including physical changes in the plant’s structure leading up to the moment of seed release.

Dr. Angela Hay, a research leader at the Max Planck Institute, emphasized that optimal seed dispersal involves more than just pressure. The study reveals that it’s a trade-off between the buildup of fluid pressure and other physical transformations that allow the fruit to eject its seeds at an optimal angle and distance.

Study coauthor Dr. Derek Moulton, a mathematics professor at the University of Oxford, was introduced to the squirting cucumber in 2022 by Dr. Chris Thorogood, a botanist. After observing the cucumbers in action, the researchers used advanced imaging techniques to capture the seed launches in detail. Moulton described how, when ripe, even a gentle touch on the fruit could trigger the explosive release.

The research team’s detailed study showed that, prior to the explosion, the fruit swelled with fluid, which also thickened the stem, causing it to stiffen and tilt the fruit to an angle of about 45 degrees. This angle, rather than a vertical launch, is ideal for ejecting seeds over a greater distance. Furthermore, as the fruit detached from the stem, the stem’s contraction caused the fruit to spin, creating a wider dispersal arc for the seeds.

This complex process ensures that the seeds are not only launched far but are also spread across a broader area, improving the chances that some will successfully germinate.

Dr. Hay remarked that studying outliers like the squirting cucumber can provide valuable insights into plant behavior that more conventional models may not reveal. The discovery also highlights that plants can perform extraordinary feats, challenging the notion that they are passive organisms.

Moulton expressed his satisfaction with the project, saying, “How many people have ever associated cucumbers with rapid motion? It’s been fascinating to uncover the mechanism behind this explosive cucumber.”