the nose fairing -- which protects the warheads and the post-boost vehicle during ascent -- on the Trident II submarine-launched ballistic missiles is made from some beautiful Sitka spruce (and some glass, but it's mostly wood).
This will not solve the "space junk" problem as the title claim. A piece of wood traveling in space at a huge speed would break any other satellite it hits, and wood does not rot in space and just dissapear.<p>This potentially solves (partially) the problem of pieces of satellites surviving the reentry after they are out of use.