I hope this appeases Amy somewhat. Though not a full gardening application like the Sunset plant guide or Armitage perennial book or public garden guide, at least coming soon is a tree guide for her iPhone.
Ah, but it's not just an online version of a regular old tree book. How it works is that you'll take a photo of a leaf and the program automatically identifies the tree for you. Programmers foresee apps able to ID a bird from a call, and more. Wow.