When I make plans to visit California's Yosemite National Park I target my trip for mid-to-late May. Mostly this is because the snow melt in the Sierra Nevada Mountains is at its peak and the park's waterfalls are overflowing and amazing.
A second reason for a late spring arrival is to see the dogwoods bloom. There are two types of dogwoods: 1) a small ground plant (not the one I'm talking about) and, 2) trees that grow up to 30 feet tall having flowers about 3 inches wide.
Yosemite has many mountain dogwoods which are beautiful in bloom, as you can see. Dogwoods are especially plentiful around the Merced River in Yosemite Valley, but are quite common along most of the park roads, making a great drive even better.