Thanks to Dad’s assistance, and his deft employment of his trusty arboreal connections, we have solved the mystery of the white flowering tree.
Here is what David Giblin of the University of Washington Herbarium has to tell us:
"Looks like Styrax japonica in the Styracaceae. There is one North American genus in the family - Halesia. There are several temperate genera that are grown ornamentally - Sinojackia and Pterostyrax are the most common."
Our heartfelt thanks to Dr. Giblin for his assistance in identifying this beautiful tree!
According to my research, this tree is commonly referred to as a Japanese Snowbell tree. I can’t be 100% certain of this particular cultivar, but after looking around I believe it may be the Emerald Pagoda variety.