Syringa

An upright, multi-stemmed, suckering deciduous shrub in the olive family, grown for its intensely fragrant mid-to-late-spring (May) bloom of lilac-purple flowers in large conical panicles. Native to southeastern Europe and cultivated in North America since the early 1600s, it matures to 12 to 16 feet tall with blue-green, pointed-ovate to heart-shaped leaves. It needs cold winters and cool summers - and offers few ornamental features after bloom, with leggy form, no fall color, and summer powdery mildew.

Persian lilac (Syringa × persica) is a compact deciduous lilac (Oleaceae) of uncertain hybrid origin, thought to arise from a cross between Syringa × laciniata and S. afghanica; it has been cultivated in European gardens for centuries and carries no confirmed wild native range (Wikipedia). Growing 4 to 8 feet tall and spreading 5 to 10 feet wide with gracefully arching branches, it produces abundantly fragrant pale-lilac panicles in spring and tolerates more warmth than common lilac (USDA zones 4a–7b per NC State Extension; some sources extend the warm edge to zone 9). The honest catch is powdery mildew: this lilac is highly susceptible and must be sited with excellent air circulation and pruned to an open centre, or the mid-summer foliage will be heavily disfigured - a near-certainty in humid, sheltered spots. (Note: this is the Oleaceae lilac, NOT the toxic Melia azedarach that shares the name.)