Moon Trees: The Story of the Seeds That Went to Outer Space

NASA, the U.S. space agency, has learned a lot since the 1940s about the effects of extreme conditions during space travel on the human body, from bone density loss to changes in the immune system to effects of radiation. But what do we know about how space travel affects plants? One of the early attempts to find out came in 1971 when the Apollo 14 mission carried hundreds of tree seeds to the moon. 

After studying the seeds back on Earth, the “moon trees” were planted across the United States for the nation’s bicentennial, and for years after they were largely forgotten about. But the experiment endures as a notable early step in understanding how space affects plants.

How Seeds Survived Space

When astronaut Stuart Roosa blasted off on the Apollo 14 moon mission in 1971, he carried the moon tree seeds sealed in tiny plastic bags. The idea originated with U.S. Forest Service chief Ed Cliff, who knew Roosa back when he was a USFS smokejumper. Cliff contacted Roosa and initiated a joint effort with NASA that garnered publicity for the Forest Service but also had a real scientific purpose: to further understand the effects of deep space on seeds. 

It wasn’t the first time seeds had traveled to space. In 1946, a NASA V-2 rocket mission carried maize seeds to observe the effects of cosmic and ultraviolet (UV) radiation. Seeds in space are exposed to powerful radiation, low pressure, and microgravity.

But they also have unique defenses. Many seeds carry duplicate genes that can step in when genes are damaged. The outer coating of seeds contains chemicals that protect their DNA from UV radiation. Such early experiments helped lay the groundwork for much more advanced research into how these processes aid seeds’ survival in space.

Roosa, the command module pilot for the Apollo 14 mission, carried his sealed bags of tree seeds inside a metal canister. They came from five species: loblolly pine, sycamore, sweetgum, redwood, and Douglas fir. The seeds orbited with Roosa while commander Alan Shephard and lunar module pilot Edgar Mitchell set foot on the moon. 

Upon returning to Earth, both astronauts and seeds underwent a decontamination process to ensure they weren’t inadvertently bringing back dangerous substances. During decontamination, the canister popped open and the seeds scattered. Exposed to the vacuum inside the decontamination chamber, the seeds were feared dead. But hundreds survived to become saplings. 

Where Are Moon Trees Today?

The saplings were planted at schools, government properties, parks, and historic sites around the country—many in conjunction with the 1976 bicentennial celebrations. Some were planted next to their control counterparts, which had remained behind on Earth. NASA reported that scientists found no discernable differences between the earthly and “lunar” trees.

Some moon trees found homes in sites of special historical significance. A loblolly pine was planted at the White House while others went to Washington Square in Philadelphia, Valley Forge, the International Forest of Friendship, the Alabama birthplace of Helen Keller, and various NASA centers. A few trees even traveled to Brazil and Switzerland, and one was presented to the Emperor of Japan. 

Many of the original moon trees have now died, though at about the same rate as the control trees. Some died of disease, others of infestations. A moon tree in New Orleans perished after Hurricane Katrina in 2005. Fifty years later, the surviving trees have reached an impressive size.  

The moon trees might have been largely lost to history if it weren’t for Indiana teacher Joan Goble. In 1995, Goble and her third-grade class came across a tree at a local Girl Scouts camp with a modest plaque that said “moon tree.” After some poking around on the then-rudimentary internet, she found a NASA web page with the email address of an agency archivist, Dave Williams, and contacted him. 

Williams, a planetary scientist based at the Goddard Space Flight Center, had never heard of the moon trees—and soon discovered he wasn’t alone. NASA hadn’t even maintained records of where the trees were planted. But eventually, Williams tracked down newspaper coverage of the bicentennial moon tree ceremonies. He created a web page to document the surviving trees and invited people to contact him about moon trees in their community. So far, about 100 original moon trees are listed on the site. 

Today, the second generation of moon trees, sometimes referred to as “half-moon trees,” have been grown using cuttings or seeds from the originals. One of these, a sycamore, is planted at Arlington National Cemetery in tribute to Roosa, who died in 1994.

The "Roots" of Plant Research in Space

The original moon trees may not have led to big breakthroughs, but they serve as tangible reminders of how far plant science in space has come. One area of plant research on the International Space Station today explores how astronauts can be healthier and more self-sufficient on long missions by growing their own food. 

The space station garden grows a variety of leafy greens, which may help protect against bone density loss, among other ailments associated with space travel. Some plants already provide fresh produce for crew members. In the future, scientists hope to grow berries and beans high in antioxidants, which may help protect astronauts against radiation. 

Scientists on the International Space Station are also observing how space affects plant genes, and how plants might be genetically modified to enhance nutrition. In addition, studying plants may help scientists better understand the effects of space travel on humans, including clues to how being in space causes bone and muscle loss. All of this data will support long-term space expeditions. 

The moon trees were a modest but memorable step, and they endure as living links to those early moon missions. They serve not only as a reminder of the distance traveled by humans beyond Earth but how precious and unique is the planet we come from.