On February 5, 1971, crew members of NASA's Apollo 14 mission became the third set of astronauts to set foot on the moon. This mission is perhaps most famous for Alan Shepard's extraterrestrial golf outing—Shepard snuck a makeshift six iron into the capsule and hit two balls out of the biggest (and lowest-gravity) sand trap in history. But Apollo 14's legacy extends beyond golf. Namely, it includes hundreds of "Moon trees" planted down here on earth.
While Alan Shepard and Edgar Mitchell walked, golfed, and performed studies on the moon for 33 hours, Command Module Pilot Stuart Roosa stayed in lunar orbit aboard the Kitty Hawk. In his pack, Roosa kept over 400 seeds for five different types of trees—Douglas Fir, Loblolly Pine, Redwood, Sycamore, and Sweetgum. Before becoming an astronaut, Roosa was a U.S. Forest Service smoke jumper. Ed Cliff, the Chief of the Forest Service in 1971, contacted Roosa to see if he'd be up for bringing the seeds along with him as an experiment. The experiment was approved, and the hundreds of seeds stayed in the command module as it orbited the moon 34 times.
The seeds' long commute looked to be for naught, though, as their storage canisters cracked open during the astronauts' decontamination procedures on Earth, mixing all the samples together. The seeds were thought to be unsalvageable, but two Forest Service stations managed to successfully germinate nearly all of them. The saplings were given to different state forestry organizations (as well as other countries and dignitaries) as gifts. There are currently dozens of known Moon trees planted around the country, some perhaps in parks you visit regularly but had no idea were home to such well-traveled scenery.
NASA has a list of all the known locations of these trees, but there are many that went unaccounted for. There is an ongoing search for these incognito trees being led by NASA astronomer Dave Williams. If you have a lead, contact him at email@example.com.