Walks in the fall can be a little more educational if you use Leafsnap, an electronic field guide that uses your phone's camera as a visual recognition device. Simply snap a picture of the leaf against a light-colored background and it will search for the matching species in the database. The GPS information encoded in your iPhone photos also provides the app important species distribution information to the database.
Leafsnap is free and was developed by Columbia University in New York, the University of Maryland and the Smithsonian Institution. It was a project that combined the talents of computer scientists at Columbia and Maryland and the Botany Department of the National Museum of Natural History. The app has cataloged species native to the New York and Washington, DC, regions. They are assisted by students and staff at all of those institutions and by the members of the Washington Biologists' Field Club.
When you are out in the woods or around your neighborhood, launch the app and 'snap' a picture of your leaf and the app will compare it to the other leaf shapes in the field guide. It will ask you to choose the right shape from a small selection and then it will provide you other photos that help you identify it. The user also can search by common and scientific names, providing photographs of the tree's fruit, seeds, bark and other information. All of the 'snaps' are cataloged.
The app also has games to identify leaves, flowers and fruits. Walking through my neighborhood in spring I often wondered what species produced a particular flower. Now I could use this app and learn more about the tree. There is basic information in the app, but it also links out to the Encyclopedia of Life, which is a Wikipedia-like collaborative encyclopedia that hopes to document all of the Earth's living species.
Leafsnap is available on iPhone and iPad, but an Android version is being developed.
Leafsnap is a great way to rediscover your inner botanist, or answer the questions that you are asked by your junior naturalist. I finally know that the tree outside my front door is a Yoshino Cherry—the same tree that blooms along the Tidal Basin—and that it is a Spanish Oak Tree that shares its abundant pollen in spring.