Lilacs (Syringa species) consist of about 2 dozen species and nearly 500 cultivated varieties i.e. cultivars. They have been in America since early settlers brought them from Europe around 1700. Some lilacs begin to bloom in early May while others extend the season into late June. The majority of lilacs and their cultivars will bloom about the third week of May in the Upper Midwest.

Although a lot of effort has gone into hybridizing lilacs, they all still have flower colors in shades of purple to blue to white. Lemoine Nursery of Nancy, France has been responsible for creating a large number of lilac cultivars in the past century. These are the "French" lilacs found in many landscapes.

In an effort to keep all the lilacs in some type of order, groups have been developed that include lilacs with similar bloom times in USDA Hardiness Zone 5. Individual species may flower earlier or later depending on your Zone, however, the relative ORDER of bloom should be the same regardless of location.