The United States possesses one of the most diverse temperate floras in the world, comparable only to that of China.
While most of the United States has a temperate climate, Alaska has vast arctic areas, the southern part of Florida is tropical, as well as Hawaii (including high mountains), and the U.S. territories in the Caribbean and the Pacific, and alpine summits are present on many western mountains, as well as a few in the Northeast.
Finally, the U.S. shares long borders with Canada and Mexico, and is relatively close to the Bahamas, Cuba and other Caribbean islands, and easternmost Asia.
The native flora of the United States has provided the world with a large number of horticultural and agricultural plants, mostly ornamentals, such as flowering dogwood, redbud, mountain laurel, bald cypress, southern magnolia, and black locust, all now cultivated in temperate regions worldwide, but also various food plants such as blueberries, black raspberries, cranberries, maple syrup and sugar, and pecans, and Monterey pine and other timber trees.
Thousands of other native U.S. vascular plants are considered rare, threatened, or endangered, either globally (rangewide) or within particular states.