Bauhinia alba - White Orchid Tree
Orchids don't grow in trees, but this lovely Bauhinia could convince you otherwise. In spring, it covers itself with a profusion of fragrant white blossoms 5" across. Serious showstopper. It grows quickly to 15' or 20' with a short trunk and spreading branches, not too big for a backyard but showy enough for a botanic garden.
The large white blooms and heart shaped leaves give a very tropical look to any landscape, but this tree is fiercely drought-tolerant, easy to cultivate and requires little attention. Native to India, it's evergreen in zones 9-11, needs full sun and sandy soil, whatever water falls from the sky. The blooms are followed by masses of curly pods, intriguing, but they will land on your lawn. Plant where you can rake them up easily.
Orchid Tree can also be grown indoors in bright light and kept small with pruning. Older seeds should be soaked in hot water, then planted in moist sandy soil and kept warm. These seeds are so fresh that they're sprouting without encouragement. Easy.