Blooming in the Sunken Garden at Phipps Conservatory, Pittsburgh.
There are two species of Catalpa (C. bignonioides and C. speciosa), both widely planted and hard to tell apart from each other. We identify this tree as C. speciosa because the Homewood Cemetery, where it was blooming in early June, identifies it as such. The Homewood Cemetery is also an arboretum, which is a beautiful combination.
Catalpas bloom for a brief period and then drop their thousands of blossoms on the ground. Since the flowers fall whole, and since they are rather large and heavy, the effect can be almost like snow.