The short version: Apollo 14 command module pilot Stuart Roosa carried hundreds of tree seeds around the Moon in 1971. After splashdown, the U.S. Forest Service germinated them, and many seedlings were planted across the U.S. and beyond as living Bicentennial markers.
1971
Seeds from sycamore, loblolly pine, sweetgum, redwood and Douglas fir orbit the Moon aboard Apollo 14.
1975-76
Moon Tree seedlings are planted at capitols, parks, universities, schools and public gardens.
Now
Many original records were incomplete, so the search for surviving Moon Trees is still part history project, part treasure hunt.