In the 1700s, Swedish physician Carolus Linnaeus pursued his secret passion for botany and classification, developing the plant classification scheme that we still use today. Identifying a flowering tree requires determining where it fits into that classification scheme, using observations about its structure and behavior to identify its species.
Linnaeus's principles of taxonomy classified plants according to their relationship to each other rather than relying on hierarchical principles used by theorists before him. Plants that belong to more taxonomic categories are more closely related, so identifying a species involves starting at the top and working down. All plants belong to the plant kingdom, and all flowering plants--including trees--belong to the angiosperm genus, so the next logical step involves determining the family to which your flowering tree belongs, which requires you to observe its characteristics.
Identifying a flowering tree requires careful observation of its characteristics. The National Audubon Society recommends recording notes, making sketches and taking photographs to aid you in identification. Note details about the tree's habitat--does it occur often in forests, for example, or tend to grow on its own?--and the geographical location. NAS further recommends repeated visits throughout the year to determine when the tree flowers, produces fruit and loses its leaves.
Leaf shape and arrangement provides valuable clues for identification. The National Audubon Society recommends beginning by determining if leaves occur opposite each other or alternate along the branch. Next, determine if leaves are simple, consisting of one leaf, or compound, containing many leaflets. Also observe the basic shape of the leaf, its size, the arrangement of leaf veins, the texture of its edges and its autumn color.
Flowers and Fruit
Most people observe the color of the flower immediately, but it is also important to note the number, shape and size of the petals, as well as the flowers' arrangement on the branch. When flowers drop from the trees, they leave behind nuts and fruit that contain their seeds, so observing the size, color, shape and other qualities of the nuts and fruit provide further clues to help you with identification.
Your local library likely holds field guides about identifying trees and flowers and may even have books specific to your region. Once you have your observations, consult a field guide to try to find a match. Consider regional and seasonal information as well. It is unlikely, for example, that you will find a tree limited to the subtropics growing in Canada, and if your tree produces flowers in late summer, it is unlikely that it is the same species listed as flowering in early spring. If you find similar trees, however, that do not completely match your specimen, they may provide clues about the family to which your tree belongs. Don't be put off by botanical terminology--look up new words as you encounter them, and you'll soon develop fluency.