When most people think of lilacs, they think of the fragrant, old-fashioned common lilac (Syringa vulgaris), which blooms for a few weeks each spring, but the genus is quite diverse. By selecting carefully, it is possible to have two months of spring bloom (particularly if the weather is cool), plus some repeat flowering in early fall, and even fall foliage color. For the earliest blooms, choose hybrid S. x hyacinthiflora, followed by common lilacs, which offer the longest blooming, largest flowers with the best fragrance. Extend the lilac season to summer with species such as S. patula, which also has good fall color, and tree lilacs such as S. x chinensis 'Saugeana' or the Japanese tree lilac (S. reticulata).

Most lilacs grow happily in Zones 4-7, but some are adaptable farther south. Common lilacs, natives of somewhat chilly mountainous zones, require a cold period each winter for their flowers buds to mature and bloom the following spring. Lilacs don't take kindly to the Deep South or the desert, but some cultivars, such as 'Blue Skies,' 'Exel,' and 'Sister Justina' have been bred for warmer regions (Zones 8 and 9). The cutleaf lilac (S. laciniata) also handles some heat, and its fine-textured foliage is particularly attractive.