Nodding lilac, Syringa reflexa, grows 10 to 12 feet tall and wide. The purplish pink flowers are produced on 4 to 10 inch long panicles. This species is not fragrant and is hardy for growing zones 5 to 7. The common lilac, Syringa vulgaris , grows 10 to 15 feet in height with a spread of 6 to 12 feet. The flowers are extremely fragrant and appear in early to mid-May on panicles originating in pairs from the terminal buds.
Numerous varieties are available with white, violet, blue, lilac, pink, and magenta flowers.
Varieties are available with single and double flowers. The Chinese lilac, S. x chinensis, is a hybrid between S. x persica and S. vulgaris. This shrub is round-topped with arching branches. It flowers more profusely than the common lilac and grows 8 to 15 feet tall with a similar spread. Flowers are purple lilac in color and appear in mid-May.