'Henri Robert' is one of the author's favorite French hybrids.
All lilacs belong to the genus Syringa, with about 20 species and hundreds of cultivars commonly cultivated. Most species are native to Asia. None are native to North America. Many of the species, or wild, lilacs look quite different from the popular common lilac, S. vulgaris, with its heart-shaped leaves and large flowers which bloom about the third week of May here in Boston.
Native to eastern Europe, the common lilac was introduced to western Europe before 1600 and likely to North America from there. It wasn't until the 1800s that named cultivars were bred. Around 1900, so many of these better cultivars came from France that the term "French Hybrid" is often used to describe all cultivars of the common lilac, even though many were bred in other European countries or North America.
Beyond the common lilac, other Syringa species have some very interesting traits. All have pleasant fragrances, with some quite different from S. vulgaris.
The lilac usually considered the most fragrant is a Chinese native—S. pubescens. It has small, white flowers tinged with purple. The fragrance is sweet and spicy, very different from the traditional "lilac" scent.