Syringa is a genus of about 30 species of lilac trees and shrubs native to Europe and Asia and widely grown as an ornamental in North America.For many, “lilac” brings to mind the common lilac, Syringa vulgaris, known for its fragrant masses of purple, lavender and white blooms in May. However, the common lilac is susceptible to several diseases and insects, including powdery mildew, bacterial blight, scale and borers. Some resistant cultivars have been reported, and there are other less susceptible species and hybrids available.