Snow in early summer is visually invoked by the masses of blooms on Styrax japonicus. Common or Japanese snowbell is the species of Styrax most often grown locally.
The UK trade magazine Horticulture Week has an excellent article about species of Styrax, including a section on “What the Specialists Say” regarding growing these small trees and shrubs (Styrax japonicus will typically grow to about 10m (30 ft.)). The cultivar ‘Fargesii’ is considered a more robust selection overall, with larger flowers and leaves. This is recognized on the Royal Horticultural Society’s page for Styrax japonicus ‘Fargesii’; also notable is that it is a recipient of the Award of Garden Merit.
To read previous entries on species of Styrax, check out the Styracaceae tag.