The common lilac, Syringa vulgaris, is originally native to Europe, but came to North America as early as the 18th century. Lilacs are popular garden and landscape plants, and make excellent borders, hedges and tall screens. These plants prefer slightly acidic to slightly alkaline soil with plenty of well-drained soil The lilac tree is notable for its fragrant, richly colored flowers, which it produces in abundance.
Appearance
Lilacs are known for their large, showy flower clusters. Most varieties produce large groupings of smaller flowers, known as panicles. These panicles grow at the end of the branches, and can be 4 inches to 8 inches long. Eventually, they dry up, forming fruit capsules where the flowers were. These can propagate the lilac tree, but should generally be removed in landscape plantings.
Color
While the lilac bush gives the color its name, these plants don't just produce purple flowers. Lilac varieties may also grow white, dark blue, pink or wine-colored blossoms. Some lilac trees are produced by grafting cuttings from a bush that produces attractive flowers onto a hardier rootstock. According to North Dakota State University's website, this process can produce a surprise if the grafted stock dies back. The rootstock begins to grow more vigorously, and your lilac bush may appear to chance colors from one season to the next.
Structure
The common lilac produces many tiny, four-petaled flowers in clusters known as thryses. Rare examples may produce five petals. The thryses are attached to a central stem. The entire flower structure is called a spike or panicle. Flowers open in order from the bottom to the top of each thryse. The open flowers are connected to the plant by a long tube, relative to their width. This tube contains the anthers and the stigma, the reproductive parts of the plant. After pollination, each flower becomes its own fruit capsule.
Season
Lilac bushes bloom primarily in early summer. In northern parts of the United States, the lilac is a May-blooming plant. It may produce flowers as early as April in some warmer climates, or as late as June in cooler regions. Lilacs do not do well in extremely warm regions, as they suffer from heat damage.
Problems
Not all lilac bushes flower readily. Some are reluctant bloomers, due to inadequate sunlight, too much fertilizer or extremely rich soil, or poorly-timed pruning. Prune lilacs in spring, immediately after the flowers fall, to avoid removing next year's buds. Lilacs also take a while to bloom. Most won't produce flowers for five to seven years after planting.
