The Bloomerang lilac (Syringa ‘Bloomerang’) is a highly sought-after shrub because it offers a sustained flowering display, unlike traditional lilac varieties that bloom only once in the spring. This modern cultivar is bred to rebloom, providing fragrant flowers from late spring through to the first frost of autumn. Because of this extended flowering cycle, the common pruning wisdom for traditional lilacs—which bloom exclusively on old wood—does not apply, requiring a different approach and specific timing to maximize flower production.
Understanding the Bloomerang Difference
The ability of the Bloomerang lilac to bloom repeatedly is linked to its distinct flowering habit. Traditional lilacs set flower buds on old wood, resulting in a single spring bloom. Bloomerang produces flowers on both old wood and the new wood that grows during the current season.
The primary spring bloom occurs on the previous year’s stems. After this initial display, the shrub begins vigorous new growth, and it is on these fresh stems that the plant sets subsequent flower buds. This continuous process allows the plant to cycle through multiple flushes of blooms from mid-summer until cold weather arrives.
The Critical Timing for Primary Pruning
The main structural pruning of a Bloomerang lilac must occur immediately after the initial spring bloom has completely faded, typically in late spring or early summer. This timing is deliberate because it allows you to remove spent spring flowers without sacrificing the flower buds that the plant will form for the following year’s spring show. Pruning at this time also stimulates the development of new shoots that will produce the summer and fall rebloom.
The technique for this primary prune should focus on shaping the shrub and encouraging overall health, while avoiding aggressive cuts. Begin by removing any dead, damaged, or crossing branches to improve air circulation within the canopy. To manage the size and shape, you can lightly cut back the entire shrub, but remove no more than one-third of the total plant material in any given season.
When making the cuts, use clean, sharp bypass pruners to trim the branch tips back to a healthy set of leaves or a lateral branch. This encourages the formation of multiple new growth points just below the cut, which will be the sites for subsequent waves of summer blooms. This light pruning is distinct from the severe rejuvenation pruning often used on overgrown traditional lilacs.
Encouraging the Second Bloom Through Deadheading
After the main structural prune, the ongoing maintenance throughout the summer involves deadheading, which is the removal of spent flower clusters. Deadheading is a simple process where you snip off the faded flower head, or panicle, just above the first set of healthy leaves below it. This action prevents the plant from expending energy on developing seeds.
By redirecting the plant’s energy away from seed production, you encourage it to channel those resources into new vegetative growth, which is exactly where the next set of flower buds will form. While the Bloomerang will rebloom even without deadheading, consistently removing the spent blooms throughout the summer will significantly increase the number and size of the late-season flower flushes. This maintenance should continue regularly from early summer through mid-summer to maintain a neat appearance and maximize the fragrant display.
Avoiding Common Pruning Mistakes
The most common mistake when caring for a Bloomerang lilac is treating it like a traditional, once-blooming variety. Pruning the shrub in mid-to-late summer, fall, or winter will result in the loss of next spring’s blooms. Since the Bloomerang sets its initial buds on old wood, any pruning outside of the window immediately following the first spring bloom risks removing those developing buds.
Similarly, avoiding overly aggressive pruning is important, as this can delay or severely diminish the summer rebloom. While the plant can tolerate a trim, heavy pruning removes too much of the new wood that would have been responsible for the second flowering cycle. By adhering to the late spring timing and focusing on light shaping and deadheading, you ensure the shrub maintains both its structural integrity and its multi-season flowering habit.