Hydrangeas are a beloved feature of the New England landscape, particularly in coastal Massachusetts. Gardeners often ask when the flowers will appear, but the timing of the annual bloom is not uniform. It is determined by the specific variety planted and the unpredictable Massachusetts climate. Understanding the difference between the main types of hydrangeas is the first step in predicting the summer display in your garden.
The Standard Blooming Season in Massachusetts
The overall window for hydrangea flowering in Massachusetts generally begins in late June and continues through the autumn. The earliest varieties start showing color around the third or fourth week of June, coinciding with the start of summer. The initial flush of blooms carries through July and August, with the peak display occurring mid-summer. Many varieties hold their flowers, which gradually change color, well into September and sometimes October.
Old Wood vs. New Wood: The Key to Timing
The primary factor dictating when a hydrangea blooms is whether it sets flower buds on “old wood” or “new wood.” Old wood is the growth from the previous year, meaning the plant forms its flower buds in late summer and autumn. These buds must successfully survive the entire winter to produce flowers the following season.
Conversely, new wood refers to the fresh growth that emerges in the current spring. Hydrangeas that bloom on new wood form their flower buds and bloom on those same stems within the same growing season. This provides a defense mechanism against harsh winters, as the flower-producing buds do not exist until the winter is safely past. This distinction determines both the bloom time and the correct pruning schedule.
Specific Bloom Schedules for Common Hydrangea Types
The specific bloom schedule depends entirely on the type of hydrangea grown. The classic Bigleaf hydrangea (Hydrangea macrophylla) is the most common old wood bloomer and is usually the first to flower, typically starting in mid-to-late June. These plants rely on the previous year’s stems to survive the winter for an early-summer display. Many modern Bigleaf cultivars are remontant, meaning they bloom on both old and new wood, providing an initial flush in June and a secondary bloom later in the season.
The Smooth hydrangea (Hydrangea arborescens) is a new wood bloomer, with the ‘Annabelle’ cultivar being a prime example. These varieties generally start flowering slightly later than the Bigleaf types, with blooms appearing from early to mid-July. The new growth mechanism ensures a reliable annual bloom, as the flower buds are not susceptible to winter damage.
The Panicle hydrangea (Hydrangea paniculata), including varieties like ‘Limelight,’ is also a new wood bloomer but is typically the latest to flower. These are the hardiest types, and their blooms usually begin to emerge in mid-to-late July. Panicle hydrangeas often peak in August and continue to provide color and structure well into the fall, transitioning from white or lime green to shades of pink and red.
Climate Factors and Post-Bloom Pruning
The timing and abundance of the bloom are highly susceptible to local weather patterns, especially for old wood varieties. Late spring frosts, even in May, can damage the pre-formed flower buds on Bigleaf hydrangeas, often resulting in no flowers for the season. Extreme winter temperatures falling below 10°F can also kill exposed buds, a common issue in the state’s colder hardiness zones 5 and 6. New wood bloomers avoid these delays or failures by developing buds later.
The wood type also dictates the precise timing for maintenance after the flowers fade. Old wood bloomers must be pruned immediately after flowering, typically by late July or early August. This timing allows the shrub enough time to develop new growth and set the flower buds for the following year before autumn. In contrast, new wood bloomers (Smooth and Panicle hydrangeas) offer greater flexibility. Since flower buds do not form until the current spring, these plants should be pruned during the dormant season, such as late winter or very early spring, without risking the current season’s flower production.