The beloved lilac (Syringa), a member of the olive family, is known for its fragrant blooms that signal the arrival of spring. Whether these shrubs bloom more than once a year depends entirely on the specific variety planted. While traditional types offer one grand performance, modern breeding has introduced varieties with the ability to flower repeatedly throughout the growing season, allowing gardeners to enjoy the classic scent and color for a much longer period.
The Traditional Lilac Bloom Cycle
Most traditional lilacs, such as Syringa vulgaris, display a single bloom period in late spring, typically around late April or May. This initial flowering lasts for a relatively short time, often only two to six weeks. This duration depends on the specific cultivar and local climate conditions.
This single bloom cycle is a result of the plant’s natural development process. Lilacs set their flower buds on “old wood,” meaning the branches that grew during the previous summer. Immediately after the spring bloom fades, the shrub directs its energy toward developing the new terminal buds for the following year. This process takes the entire summer and fall, concluding with a necessary period of cold dormancy over the winter to trigger the buds to open in the spring.
Introducing Reblooming Lilac Cultivars
The possibility of a second bloom comes from remontancy, a horticultural phenomenon describing a plant’s ability to flower more than once in a single season. This trait is not natural to the common lilac but has been engineered into specific modern cultivars. These shrubs have the capability to set flower buds on both the previous year’s growth and the new growth produced during the current summer.
The most recognized examples are the varieties in the Bloomerang series. These reblooming lilacs typically produce a heavy flush of flowers in mid-to-late spring, similar to traditional types. Following a brief rest in June, the plants begin to bloom again in mid-summer, often continuing their floral display until the first hard frost of the fall. The second bloom is generally lighter and the flower clusters, or panicles, are smaller than the initial spring burst, but they still provide welcome color and fragrance for months.
Encouraging a Second Bloom
Owners of reblooming lilacs can take actions to maximize the summer and fall rebloom. The most effective maintenance step is deadheading, which involves removing the spent flower clusters immediately after the primary spring bloom finishes. This process redirects the plant’s energy away from producing seeds and encourages new growth that will set the next round of flower buds.
Ensuring the plant has adequate resources during the summer months is important for the second bloom cycle. The continuous effort of producing flowers twice requires consistent watering, especially during dry spells. A light application of a slow-release fertilizer, one that is higher in phosphorus to promote flowering, can be beneficial shortly after the spring bloom to support new flower development. These care steps are specifically for reblooming types, as traditional lilacs do not require this post-bloom encouragement.