One of the features you can employ when attempting to tell one tree apart from another is to look carefully at their flowers during the spring, when most come into bloom. The flowers are the reproductive parts of the tree, eventually turning into some sort of fruit or nut that contains the seeds of the tree. These flowers differ in color, shape, size and other traits that can give a tree its own identify and help you to recognize the individual species.
Study the colors of the flower on a particular tree. Note where on the flower different colors or marking occur. The northern catalpa is a good example of a tree with a very distinctive color pattern on its flowers. The catalpa flower has white petals flecked with orange, purple and yellow.
Look at the structure of the flower. While many trees have what you consider "classic" flowers, others, like the yellow birch, have catkins. These do not look like a normal flower complete with petals, but rather like tassels hanging from the birch tree, with some male and others female. Many trees will be either male or female, with the flowers of each sex differing from each other. This is true on a tree like the persimmon.
Determine the timing of the flower's appearance. Some trees will not flower until the leaves are developing or already open, while many will have their flowers fully emerged long before the leaves begin to open up. The redbud has no leaves when its pink flowers come forth in bright clusters. The American plum is another tree that has white flowers before its leaves come in.
Consider the overall shape and make-up of the flower. The tulip tree takes its name from its flowers, which do closely mimic the popular tulips that burst open in the spring. Apple trees will normally have flowers with five petals of the same size surrounding the center of the blossom. The flowering dogwood has four large white bracts that you could easily mistake for true flower petals, with a notched end on each one. They radiate from a central point in which the actual flower sits.