The Amazing Tale of the Cherry Pit from Space

Everyone loves a mystery, and if it comes from outer space so much the better. It’s no wonder, therefore, that stories have been popping up everywhere over the past few days about a cherry tree that has at least some scientists flummoxed. On April 1st, the tree burst into flower on the grounds of a Buddhist temple in Gifu, in central Japan. That would hardly be noteworthy, given that this is exactly the time of year for the country’s famous cherry blossoms. But the tree is just four years old, and it wouldn’t normally be expected to produce flowers until the age of ten.

An intriguing explanation has emerged. Back in 2008, at the behest of the Japan Aerospace Exploration Agency, astronauts carried two hundred and sixty-five cherry pits from a nationally beloved, twelve-hundred-and-fifty-year-old tree known as Chujohimeseigan-zakura to the International Space Station. When these pits came back to Earth, eight months later, a few were planted, but with low expectations; according to monks at the temple where the original tree stands, its seeds had never sprouted before.

To everyone’s surprise, however, a few of these seeds did sprout into saplings, at least one of which grew to a height of around thirteen feet in just four years—another surprise, say the botanists. “It is difficult for us to judge why this has happened, but one reason the tree has grown so fast may be related to space rays,” Kaori Tomita-Yokotani, a scientist at the University of Tsukuba, told the South China Morning Post. The tree was starting to sound like the arboreal version of the Fantastic Four, who acquired their own amazing powers during a ride aboard a rocket ship. Some suggested that the tree’s premature blossoming, as well as the fact that its flowers have only five petals each (the parent tree’s flowers typically have thirty), had similarly sci-fi explanations.

The tale started to spread, fuelled by headlines like “ ‘Space Cherry’ Tree Stumps Botanists,” in USA Today, and “Mysterious Growth of the ‘Space Cherry,’ ” in the Daily Mail; scientists declared themselves “baffled,” “stunned,” and “amazed.”

But maybe they should relax. At least a couple of scientists are more surprised by the attention this tree is receiving than by the tree itself. Melanie Sifton, the vice-president for horticulture at the Brooklyn Botanic Garden, told me that “the time it takes for a tree to bloom can depend a lot on growing conditions, not just on the variety.” The seeds, she explained, are only part of the story; the trees have to be dusted with pollen from other trees before they can flower. “The young trees could easily have been pollinated by a different variety,” she said, which could have affected the flowers. “There are lots of possible variables, and we really don’t know what they were.”

Margaret Pooler, a plant geneticist and an expert on flowering trees at the U.S. Department of Agriculture’s National Arboretum, in Washington, D.C., had a similar reaction. “Ten years for a cherry tree to blossom sounds pretty long to me,” she told me. She is also unimpressed by the space tree’s sparsely petalled flowers, which she doesn’t find all that unusual, even if the parent tree had more. The same goes for the tree’s height. “It’s pretty tall, but you can have tall kids from short parents, and vice versa,” said Pooler, who recently helped clone some of the cherry trees that were planted along Washington’s National Mall and Tidal Basin in 1912.

This isn’t to say that the seeds were unaffected by their time in space—by cosmic rays, for example, or by microgravity. To claim an effect, though, you would have to show that this tree is significantly different from ordinary trees. Pooler’s and Sifton’s comments suggest that it may not be. And, even if it were, one tree out of two hundred and fifty-six seeds is a statistically tiny, and pretty much meaningless, sample; its differences could be explained by more prosaic factors, like cross-pollination with nearby trees of another species.

You would also have to show that seeds from the Chujohimeseigan-zakura that didn’t go into space and were planted under the same conditions as the space-faring seeds would sprout and grow differently. Without such a control group, any attempt to explain what’s going on is pure speculation. The National Aeronautics and Space Administration has done this sort of experiment a number of times in the past, most notably by putting potato seeds on the Space Shuttle and tomato seeds on the Long Duration Exposure Facility, a satellite that spent six years in orbit. Afterward, scientists planted the seeds, along with seeds of the same varieties that hadn’t gone to space, to test the effect of going into orbit. “Those experiments did not present results that were as dramatic as what the Japanese are reporting now with the cherry trees,” Marshall Porterfield, who oversees NASA’s Fundamental Space Biology division, told NPR.

Nobody has tried such an experiment with the cherry seeds, however, and for a very good reason: planting them wasn’t designed to be a real scientific experiment in the first place. It was simply an attempt to get Japanese schoolchildren excited about space. At that, it may well have succeeded.

Above: The Japanese astronaut Koichi Wakata holds a pack of cherry pits, on April 13, 2009. Photograph courtesy Japan Aerospace Exploration Agency.