‘Sonoma’ is an early-flowering cultivar of the choice dove tree (or handkerchief tree) – in fact, this particular cultivar is a Great Plant Pick.
Davidia involucrata is often considered to be the only member of its genus, though not always; Wikipedia discusses the occasionally recognized Davidia vilmoriniana. One species or two, the genus remains endemic to China. This wasn’t always the case, as the genus Davidia was once widespread across North America (see: Manchester, SR. 2002. Leaves and fruits of Davidia (Cornales) from the Paleocene of North America. Systematic Botany. 27(2):368-382). Dr. Steven Manchester, author of the cited paper, has included some of the images online from a fossil North American Davidia in this gallery; look for the images following the red circles (pollen grains).
UBC BG Forums BPotD Submissions Pics of the Day: Images of the species Davidia involucrata, photographed in the Riverview Arboretum (Coquitlam, British Columbia) by jimmyq@UBC Botanical Garden Forums.
Photography resource link: The Essential Landscape: Artists – Stand Up For Your Art!, an opinion piece by Guy Tal for Nature Photographers Online that advocates against the use of rigid definitions on what is considered “true” nature photography.