Asters are a varied group of common garden perennials that provide vibrant, daisy-like color in the late-season landscape. Many species, particularly the popular fall-blooming types, behave as “cut and come again” plants. Gardeners can extend the flowering period through specific pruning and maintenance techniques. This potential for repeat blooms makes asters a valuable addition for continuous color.
Pruning Techniques for Encouraging Rebloom
The direct action of deadheading is the primary way to encourage asters to produce a second flush of blooms after the first cycle fades. Deadheading involves the removal of spent flowers and flower clusters before the plant can divert energy into seed production. This action signals to the plant that it must allocate resources to creating new flower buds instead of developing seeds.
When deadheading, use clean, sharp hand pruners to make a cut just above a healthy leaf node or a new side shoot. Asters often bloom in clusters, so you may need to remove the entire cluster stem once all the individual flowers have faded. Regular removal of these faded blooms, ideally every one to two weeks, keeps the plant looking tidy and maximizes the chances of a rebloom.
Species Differences in Rebloom Potential
The vigor and timing of rebloom depend heavily on the specific aster variety being grown. Asters encompass a large group of plants, including those classified botanically under the genus Symphyotrichum. The most common garden varieties, the New England aster (Symphyotrichum novae-angliae) and the New York aster (Symphyotrichum novi-belgii), are highly responsive to deadheading.
New England asters, which tend to be taller with thicker stems, readily produce a second wave of flowers, extending their display well into autumn. New York asters, known for their smoother leaves and compact growth, also rebloom reliably, although their flowers may be slightly smaller in the second cycle. Conversely, some alpine or woody aster varieties are less likely to produce a robust second bloom after cutting.
Maximizing Bloom Duration Through Mid-Season Shearing
A technique distinct from deadheading, known as mid-season shearing or the “Chelsea Chop,” is used earlier in the year to extend the overall flowering period. This method involves cutting back the healthy, actively growing stems by one-third to one-half of their height in late spring or early summer. Performing this cut in late May or early June, before flower buds have fully formed, delays the initial bloom time by approximately four to six weeks.
This shearing forces the plant to create numerous side shoots, resulting in a bushier, shorter plant with more stems. Since these new side shoots develop and bloom later, the overall flowering season is significantly prolonged, pushing the color display deeper into the fall. For a staggered effect, gardeners can cut back only half of the stems in a clump, allowing the uncut stems to flower earlier while the chopped stems provide a later wave of blooms.