Lilac (Syringa vulgaris), a perennial flowering shrub, grows best in cooler areas of the country, though it only offers one main season of interest. The shrub's showy, fragrant blooms appear in spring in shades of pink, purple, white and pale yellow. Once the blooms fade, the lilac bush may become leggy and its leaves may attract mildew. Hardy in USDA Zones 3 through 5, lilacs may also survive winter in mild areas of Zone 2 and summer in mild areas of Zone 6 with proper care. Hardy and resilient, the lilac bush often survives in less than desirable conditions, though routine maintenance ensures the most attractive and abundant blooms in spring.
Plant lilac during the spring, summer or early fall; however, plants perform best when planted in early spring while still dormant. Choose a planting site that receives a minimum of six hours of sunlight and consists of well-drained soil. Spread a 2- to 3-inch layer of aged manure over the chosen site and use a tiller to work it into the soil to increase fertility and drainage.
Dig a hole in the soil slightly deeper and twice as wide as the root ball. Insert the roots into the hole and back-fill with soil. Water the soil thoroughly to collapse any air pockets and bring moisture into contact with the root system.
Water the lilac bush once every five days during the first year of growth to prevent the soil from drying out. Keep the soil consistently moist at all times, as lilacs become stressed during drought-like conditions. Reduce watering frequency to once every week after the first year of growth. Soak the soil to a depth of 12 inches to ensure the plant receives adequate moisture.
Feed established lilac bushes during early spring, ideally in March or April, using a 5-10-5, 5-10-10 or 10-10-10 NPK fertilizer. Apply following the instructions provided by the manufacturer for the best results. Water the soil lightly before and after fertilizing to prevent root injury.
Prune the lilac bush throughout the year to keep the plant healthy and blooming abundantly. Remove diseased or dead wood whenever necessary. Cut back excessively long branches during winter using hedge clippers. Do not cut back branches with buds forming on them, as this greatly reduces flowering the following season.