There was a fascinating article by Adrian Higgins about the Svalbard Global Seed Vault (and saving your own seeds) in last week's Washington Post ("Preserving Precious Seeds, in Norway and Your Way," 3/6/08).  The so-called "Doomsday Vault" keeps a worldwide selection of seeds safe from natural and manmade disaster deep in a Norwegian mountain.  Higgins suggests that "Svalbard may be the gardener's Valhalla: a gathering place for fallen heroes, not quite dead, as in Norse myth, but not quite alive, either."  I love this idea and think it would make a great post-apocalyptic YA novel.  Maybe someone's already written it (I haven't read a lot of post-apocalyptic YA novels); but if not, it might work!

[Somewhat related recommendation for the grownups:  The Sparrow by Mary Doria Russell.  I've lost track of who has my copy of this book (this has happened before; I think I'm on my third copy.  No one wants to give it back); otherwise I would look up the gardening reference for you.]