Hardiness zones: 3-7
Chilling requirement: Lilacs need a period of cold, or "chilling," to set flower buds. This is why they perform poorly or do not bloom at all in the warmer winters of zones 8 and higher.
Full sun: For the best and most prolific flowering, lilacs need at least 6 hours of full, direct sunlight each day.
Soil and drainage: They prefer fertile, well-drained soil with a neutral to slightly alkaline pH. Poor drainage can lead to root damage.
Heat stress: In hotter climates (the upper end of zone 7), lilacs are more susceptible to stress and pests like powdery mildew. Providing adequate moisture and good air circulation can help.