June Nature Almanac: NCAR Sycamore Soared to the Moon and Back
By Ruth Carol Cushman with Stephen R. Jones
June 2025
Colorado astronaut Stuart Roosa orbited the moon on the Apollo 14 space mission in 1971. He carried with him a Personal Preference Kit, a small bag in which each astronaut could bring along something meaningful to them. Roosa chose tree seeds to honor his time as a smoke-jumping fire fighter for the U.S. Forest Service and to test whether seeds exposed to space would germinate.
Not only did the seeds withstand the rigors of space, but they also survived an explosion during the decontamination procedure. Seeds scattered all over the vacuum chamber were carefully gathered, sorted, and eventually planted. 450 seeds germinated, and the resultant “moon trees” (American sycamore, coastal redwood, sweet gum, loblolly pine, and Douglas-fir) were planted throughout the country. The American sycamore (Platanus occidentalis) on the north side of the Fleischmann Building at the National Center for Atmospheric Research is a descendant of one of those trees.
American sycamore moon tree planted at the Cradle of Forestry in Pisgah National Forest. Photo from U.S. Department of Agriculture Forest Service.
So what happened to the original moon trees? Fewer than 100 of them remain according to the Moon Tree Foundation. The original trees now produce seeds, from which new saplings are grown and planted around the world.
Rosemary Roosa, Stuart’s daughter and president of the Moon Trees Foundation, dedicated the NCAR sycamore at the annual meeting of GLOBE (Global Learning and Observations to Benefit the Environment) in July 2023. However, the tree was not actually planted until Arbor Day on April 26, 2024 when growing conditions were better. This past April marked the one-year birthday of “our” moon tree, which is now fully leafed out and flourishing.
The American sycamore was a good choice to take into space and back. It is hardy, fast growing, and typically lives for two centuries, sometimes as long as six. Under ideal conditions, it becomes massive. The largest measured specimen tops out at 174 feet with a diameter of nearly 13 feet (uncited on according to Wikipedia). Historically, the trees were even larger. In 1774, in the Shenandoah Valley a settler and his two sons lived for almost a year in a hollow sycamore (Kercheval, Samuel. 1833. A History of the Valley of Virginia. Samuel H. Davis. p. 74.).
Sycamores may also be a fortunate choice as they have been revered by several cultures. Some Native Americans regarded them as protection against malevolent spirits, and in Celtic culture sycamores symbolized wisdom and knowledge. The word itself carries auspicious connotations. The ancient Greek word “Sukomoros” meant fig or mulberry because of the resemblance to fig or mulberry trees. That word evolved into the Old French “sichamor.” And we all know what the last half of the name means!
The moon tree tradition lives on. New batches of seeds are being carried into space aboard Artemis missions. One goal of the Moon Tree Foundation is to bring space lovers and tree huggers together to preserve Earth’s finite resources.
More on the Sycamore
One distinguishing feature of this species is the mottled greenish brown and tan bark that flakes off in sheets to reveal the smooth creamy inner bark. Sycamore balls, the spiky pods sometimes gilded for Christmas decorations, contain seeds, such as those that flew to the moon. The deeply lobed leaves resemble maple leaves and turn bright yellow-green in late summer. Sycamores grow best in wet bottomlands. As the trees age, the heartwood decays creating cavities sometimes large enough for bear dens and used by bats, owls, and wood ducks.
Leaves and seed pod of American Sycamore. Illustrated by Pierre-Joseph Redouté.
American sycamores are often crossed with oriental sycamores to create London plane trees, which are more resilient to disease and are widely used in parks and along streets.
Notable American sycamores in Boulder include the 115 foot state champion on the Naropa campus at 2130 Arapahoe and a double row of sycamores forming an “avenue” in Green Mountain Cemetery.
Other June Events
Wild orchids, including spotted coralroot (Corallorhiza maculata), calypso orchid (Calypso bulbosa), and northern bog orchid (Limmorchis spp.), bloom in wet areas of foothills and mountain canyons.
After evening thunderstorms, the loud "waaaaww" calls of courting Woodhouse toads resonate through marshes on the plains. Woodhouse’s toads and chorus frogs sound off in low-elevation wetlands where you may also see and hear Bobolinks and Wilson Snipe.
Female moose are rearing their young. Avoid walking through dense willows in the mountains, where sightlines are limited. Moose can charge and cause serious injury.
Fireflies flash their “come hither” lights at Sawhill Ponds and the meadows near the Cherryvale Trailhead from late June to early July, usually starting around 9 p.m.
Penstemons, locoweeds, mariposa lilies, sugar bowls, and orange arnica add splashes of color to meadows and trails. Hike Skunk Canyon, Bear Canyon, or Shanahan Ridge for spectacular floral displays.
We look forward to seeing recently-arrived monarch butterflies each summer, but are alarmed that there are so few butterflies or insects of any sort this year. Because Monarchs lay eggs on milkweeds, a few can usually be spotted wherever large stands of the showy pink flowers bloom.