W. × formosa Rehder is a putative hybrid between the Japanese and Chinese species, characterised by a mix of the characters of the presumed parents, having 9-15 leaflets and flowers that open more or less simultaneously. It is said to have originated as an artificial cross, W. floribunda 'Siro Noda' ('Alba') seed × W. sinensis pollen, in the garden of C. S. Sargent, Brookline, Massachusetts, in 1905. The lilac flowers have a pinkish tinge. As there is some doubt about the true parentage of this plant it is often referred to as the cultivar 'Formosa'. Plants currently available as the cultivar 'Issai', sometimes regarded as a clone derived from W. × formosa, are best referred to W. floribunda.
Twining clockwise. Leaflets 13-15. Flowers relatively small and densely packed in clusters 17-21 cm long. Standard 1.8-2 cm wide, pale violet, the wings and keel slightly darker. Early flowering. Often listed under w. sinensis but exhibits the general characters of w. floribunda; possibly a hybrid. Int. by William h. Chandler, one time Dean of Agriculture at the University of California, in 1952-3 and named after his wife. Distributed to Australia from New Zealand in 1995.