To escape damage from late season frosts in Canada, these lilacs were bred for their lateness of bloom. As a result, they extend the bloom season for shrub-like lilacs into the second week of June - at least!
As a group, unfortunately, they tend not to have the lush fragrance of the early-blooming S. x hyacinthiflora, common and French hybrid lilacs.
This group of lilacs also tend to grow larger (up to fifteen feet tall and ten to twelve feet wide) than the earlier-blooming types and don’t readily send up suckers that can be used to rejuvenate overgrown plants. Therefore, they're not good choices for small spaces unless trained as small, multiple-stemmed trees.