When Do Hydrangeas Bloom?

Hydrangeas are gorgeous summer bloomers we rely on for abundant color, full flowers, and lasting interest. They’re a hallmark of the season, cooling the display in blues, pinks, and whites or adding dynamic hues of violet, red, and chartreuse. 

As a group, hydrangeas bloom from mid-spring through early fall. However, specific bloom times vary depending on the species and variety. Climate and cultural conditions also influence when they bloom.

Here, we’ll look at types of hydrangeas, when to expect their blooms, and variables surrounding bloom time. Have fun in the garden choosing different species, like reblooming varieties, for a long-lasting bloom show.

Bloom Factors

These durable, woody shrubs grow and bloom across a wide range of climates and growing conditions. These conditions include temperature, sunlight intensity, moisture, and soil quality and contribute to when a hydrangea blooms in our individual gardens.

Species factors, like whether it blooms on old or new wood – or both – also impact overall blooming. With the right type in the right spot, you’ll enjoy carefree growers loaded with blooms.

Climate

Hydrangeas are hardy across most growing zones, and there are overlapping selections for gardeners in cold climates (with winter temperatures down to zone 3) and in hot climates (summers to zone 9). Temperature plays a role in bloom time, and the same variety in a northern climate may bloom later than its southern counterpart.

Generally, warm climates enjoy a more extended bloom season, with flowers appearing earlier in spring and lasting longer into fall. In cool climates, chilly temperatures and late and early frosts contribute to a shorter but just as prolific bloom season.

In areas with extremely cold winters, opt for panicle and smooth types for early and long-lasting blooms. Both types bloom on new wood, so there won’t be winter bud damage, and they are exceptionally cold hardy.

In particularly hot climates, consider light and water requirements. For gardeners with hot summers, place hydrangeas on the shadier side of the preferred light requirements. Provide regular water, especially until established and during dry spells.

During periods of stress, they may drop buds, flowers, and leaves. Environmental stressors include heat waves, dry spells, water fluctuations, and late or early-season frosts.

Old Wood vs. New Wood

Hydrangeas bloom either on old wood (the previous year’s growth) or new wood (the current year’s growth). Some selections bloom on both new and old wood for long-lasting bloom production. Knowing this old wood/new wood bloom sequence is helpful when pruning.

Species that bloom solely on old wood set their buds in late summer for blooming the following year. In frigid winters, these old wood buds are susceptible to freezing and dropping, meaning there won’t be a showy bloom display come summer. An old wood hydrangea pruned in the fall means a lack of flowering the following year.

Those that bloom on new wood set their buds in the spring. This late set means buds don’t endure cold winter temperatures. They emerge closer to seasonal bloom time. A new wood hydrangea takes pruning in fall or late winter and still blooms that summer.

If your hydrangea isn’t blooming and you’ve pruned heavily in the fall, removing buds set on old wood may be the issue. Or, if your area experienced a harsh winter or late freeze, buds may have been damaged by extreme cold.

Growing Conditions

Certain cultural conditions promote blooming and vigor. Too much or little of a good thing impacts bloom time and quality.

Sunlight

The amount of light needed depends on the intensity of the sun in their growing region. If your hydrangea isn’t blooming well, it may be related to too much sun exposure. Morning sun with afternoon shade protection is ideal in most planting areas.

In northern growing areas with cool climates, hydrangeas tolerate six hours of full sun with consistent soil moisture. In hot, southern climates, two to three hours of morning sun or dappled sunlight suffices.

Intense sun can burn leaves and flowers. Provide afternoon protection from direct sunlight, especially in gardens with hot summers. Some types, like bigleaf, tolerate full shade in hot growing conditions.

Water

Hydrangeas need about one inch of water per week, and potentially more during dry spells, to keep soils at medium moisture for best flowering.

Consistent moisture ensures overall health and vigor, but too much water leads to a decline in flowering and fungal issues. Avoid overly wet and prolonged soggy conditions when possible.

Overfertilizing

As heavy bloomers, these shrubs appreciate a spring fertilizer application. An organic, granular, slow-release fertilizer high in phosphorous, like 10-30-10, promotes growth and flowering.

Overfertilizing, however, means too much nitrogen, which produces leafy growth but less flowering and other plant problems. In the fall, stop fertilizing as growth slows and plants prepare for winter dormancy.

Hydrangea Types and Bloom Times

There are six commonly grown species, each with unique characteristics, from long bloom times to fall color and winter interest. 

Bigleaf

Hydrangea macrophylla features the large mophead and lacecap blooms that characterize hydrangeas. The rounded flower clusters in blue, pink, white, and purple transition to pink and green as they age for attractive flowers into fall.

Depending on the variety, traditional bigleaf hydrangeas bloom for about six to eight weeks from late spring to mid-summer in warm climates and from mid-summer to early fall in cooler temperatures. Cultivars like ‘Endless Summer’ and ‘Let’s Dance’ boast improved flowering and cold hardiness by setting buds on old and new wood. These bloom early and repeat bloom throughout summer until frost. 

These prolific bloomers require regular moisture and afternoon sun protection. Bigleaf hydrangea is hardy to zones 6-11 and some, like ‘Endless Summer’, down to zone 5.

Panicle

Hydrangea paniculata, or peegee hydrangea, features showy pyramidal blooms in colors from creamy white to lime green to pink tinged with red. Flowers appear in summer through early fall, transitioning to pink by September and October. Blooms fade to light buff in the winter for lasting texture and seasonal interest.

Panicle hydrangeas are among the toughest and easiest to grow. They bloom on new wood and are cold-hardy, best in zones 3-8 (sometimes 9). Panicles are adaptable plants tolerant of variant soils and occasional dry spells, though consistent moisture is best for flowering.

Smooth

Hydrangea arborescens, also called wild or smooth hydrangea, is native to the United States and grows across varying climates in zones 3-9. Buds emerge on new wood for white, ivory, and pink flowers, maturing to light green in late summer and tawny in fall.

The flowers appear in flat clusters from early summer through fall. They prefer partial to full shade and tolerate various soil conditions but don’t withstand drought.

Oakleaf

Hydrangea quercifolia is a North American native originating in the southeastern U.S. The upright shrubs bear lovely creamy white pyramidal blooms and deeply lobed leaves with red fall color. Blooms emerge mid to late spring through early summer and transition to pink and green by August and September.

Cultivars feature improved forms and color variations like deep rose. Oakleaf is hardy in zones 5-9 but benefits from winter protection in zone 5. Plants bloom on old wood.

Mountain

Hydrangea serrata is similar in appearance to bigleaf hydrangea, but it has a more compact form and smaller lacecap flowers. It blooms on old and new wood for a long-lasting bloom season from early summer into fall.

Mountain hydrangea and its cultivars range in pink, blue, violet, and white hues. Plants are hardy in zones 5-9.

Climbing

Hydrangea anomala is a different form of hydrangea with woody climbing vines that reach 30 to 60 feet high in optimal conditions. Large, flat-bloom clusters of fragrant white flowers emerge in late spring through mid-summer. 

Climbing hydrangeas are hardy in zones 4-8 (though they are somewhat borderline in the lowest and highest zones). Hot and humid southeastern summers stress these climbers. The subspecies petiolaris is more cold-hardy than the straight species and has larger blooms on old wood.