Mental Floss

Solved: The Mystery of the Squirting Cucumber’s Powerful Projection

The little gourd can shoot its seeds nearly 40 feet via “ballistic dispersal”—but until now, the mechanism behind the plant’s power and proliferation was poorly understood.

By Nick Keppler|
The squirting cucumber can blast its seeds dozens of feet from the parent plant. The stem and fruit of the plant have been colored green in this image.
The squirting cucumber can blast its seeds dozens of feet from the parent plant. The stem and fruit of the plant have been colored green in this image. | Adapted from F. Box, D.E. Moulton, D. Vella, Y. Bhagotra, T. Lowe, A. Goriely, C.J. Thorogood, Uncovering the mechanical secrets of the squirting cucumber, Proc. Natl. Acad. Sci. U.S.A.121 (50) e2410420121 (2024) // CC BY 4.0

While some plants just drop their seeds and hope for the best, many have some evolutionarily beneficial means of spreading them and increasing their species’ proliferation. Some seeds can blow in the wind, like the feathery pappus of dandelions. Others are eaten by animals, traveling inside the digestive system and then being … released. Some travel via Velcro-like burs that stick to and annoy hikers. 

For certain plants that are not messing around, there is what botanists call “ballistic dispersal”: the shooting of seeds over impressive distances. The pumpkin-like fruits of the “dynamite tree” of South America, for example, make a popping sound when they rupture and launch seeds as far as 100 feet. 

One of the most famous ballistic dispersers is Ecballium elaterium, a.k.a. the squirting cucumber. Upon ripening, its fruits explode and fire their goo-covered seeds distances of 10 to 20 feet or more. You can see the squirting in slo-mo at the 2:09 mark in the video below.

The mechanism of this gush of seeds has not been well understood. For a new study published in the Proceedings of the National Academy of Sciences, a group of British researchers used high-speed videography, image analysis, and mathematical modeling to examine how the diminutive gourd can blast its seeds so far and wide.

They found that a viscous fluid builds up in the cucumber’s pods over several weeks, creating a pressure system that eventually powers its projectiles.

Time-lapse photography showed that, before this pressure led to a burst, the stems changed how they stood, from straight up to slanted, lowering their angle by 45 degrees. This is necessary for disbursing seeds; no matter how strong the pressure stream, if the seeds just shot upwards, they would more likely land near, or on top of, the parent plant.

Squirting cucumbers don’t often miss, the researchers found. Over several generations, the seeds consistently reached distances of 13 to 39 feet. In nature, this ability reduces competition for resources within a population of Ecballium elaterium by spreading them out from the older plants.

Its unique dispersal method has helped the squirting cucumber spread across Europe into northern Africa and even to some temperate areas of Asia.

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