Lilacs (Syringa vulgaris) are considered large shrubs or small trees. These rapidly growing specimens typically reach a mature size of 8 to 15 feet tall and wide, though there are many variations. Lilacs grow 6 to 8 inches per year. Many send out suckers, causing some gardeners to consider them invasive. Others wouldn't be without these showy shrubs in their landscape. For two weeks in mid-May, fragrant purple panicles dangle from their branches, creating quite a spectacle.
Lilacs come in hundreds of varieties, with varying sizes and single or double blossoms ranging from purple to magenta, pink, white or violet. Manchurian or Korean lilac (Syringa patula ''Miss Kim'') is a compact shrub, reaching only 4 to 8 feet tall and 3 to 5 feet wide. It has purple buds that open to blue about two weeks after the common lilac. Meyer lilac (Syringa meyeri) and littleleaf lilac (Syringa microphylla) are even smaller specimens. The Japanese tree lilac (Syringa reticulata) is the tallest. It has creamy white flowers and grows 20 to 30 feet high.
Lilacs in bloom are a sight to behold, but the shrubs fade into the background for the rest of the year. Their blue-green foliage is quite ordinary looking without the colorful blossoms. Plant lower-growing shrubs or perennials in front of them for interest after spring. Group several lilacs together for a screen or windbreak, or use them singly as a garden accent.
Hardy in U.S. Department of Agriculture zones 3 through 7, lilacs perform best in full sun. They are easy to grow but need plenty of space for air circulation, which reduces the chance of powdery mildew. Plant in spring or fall. These shrubs bloom on old wood, so prune only after they have bloomed for the season. They may take several years to bloom after planting but are quite reliable after they are established.
Lilacs are an old-fashioned shrub. The earliest settlers to North America admired them so much they brought these plants with them. The tubular clusters of flowers are 4 to 8 inches long and appear in late spring to early summer, depending on the variety. They make excellent cut flowers for indoor arrangements. Soak them in warm water overnight to prolong their beauty.