Why Aren’t Your Hydrangeas Blooming?
Few shrubs are as dependable for adding color to the garden as hydrangeas—when the flowers cooperate. But many gardeners have found that their hydrangeas have produced few or no flowers in recent years. Several factors can be responsible, but weather and the timing of flower bud development are among the biggest.
Weather and Flower Buds
Many of the traditional hydrangeas grown in gardens, particularly bigleaf hydrangeas, produce their flowers on old wood. That means the buds for next year's flowers are already developing on the plant before winter arrives. Unfortunately, those buds can be especially vulnerable to the unpredictable temperature swings that occur during winter and early spring.
An early freeze can damage stems before the plant has fully entered dormancy. Just as troublesome are warm spells during winter. When temperatures rise, sap can begin moving through the stems, and as the plant tries to come out of dormancy, flower buds can begin to swell. If a freeze follows, the delicate flower tissue inside those buds can be killed.
In some cases, the stems themselves are killed back to the ground. In others, the stems survive but the flower buds are destroyed. The plant then leafs out normally in spring, making it appear healthy, but produces few or no flowers.
Location Can Protect Blooms
Because temperature fluctuations are such an important factor, where a hydrangea is planted can make a major difference. In areas with unpredictable winter temperatures, a protected location is preferable.
The north side of a house or the shade of a tree can help keep the soil cooler during winter and early spring. The cooler soil will hopefully delay bud development until after the hard freezes are past, reducing the chance that a sudden freeze will damage emerging buds.
Protection from early-morning sun is also helpful. If a flower bud has frozen overnight, rapid warming from the morning sun can cause additional damage.
A thick layer of mulch can provide another layer of protection. About four inches of mulch helps moderate soil temperature and can keep the ground from warming too quickly in late winter. Cypress mulch is one option because its lighter color reflects more heat than darker mulches.
Prune According to the Type of Hydrangea
Pruning is another common reason hydrangeas fail to bloom. The important question is whether the plant produces flowers on old wood or new wood.
Bigleaf hydrangeas, including the familiar mophead types with large pink or blue flower heads, generally bloom on old wood. Their flower buds are already present on the stems in late summer and fall, so pruning late in the season can remove the flowers that would have appeared the following season.
The best time to prune these hydrangeas is immediately after flowering, as the blooms begin to fade. Rather than shearing the entire plant, remove about one-third of the oldest canes at ground level. This encourages new growth while giving those new stems plenty of time to mature before winter.
Panicle hydrangeas, such as ‘Limelight,’ are different. They bloom on new wood, so they can be pruned in late winter. While they don’t need to be pruned every year, cutting them back to roughly 12 to 15 inches in late winter can produce vigorous new growth and larger flower heads. These hydrangeas are also more tolerant of full sun and generally have fewer problems with leaf diseases.
Managing Leaf Diseases
Hydrangea leaves commonly develop spots during the summer. Warm, wet conditions and prolonged periods of wet foliage can contribute to these diseases. Overhead irrigation can make the problem worse, so when watering is necessary, doing it early in the morning gives the foliage time to dry.
For plants with a history of serious leaf-spot problems, fungicides can provide additional protection. However, a few scattered spots are a cosmetic problem rather than a serious threat. If a large portion of the green tissue is lost, the disease can begin to affect the plant's overall health by reducing its ability to produce energy for the root system and next year's growth and flowers.
Soil and Flower Color
Soil pH is particularly important when growing bigleaf hydrangeas if flower color is a consideration. More acidic soil, around pH 5, tends to produce blue flowers, while a pH closer to 6 to 7 generally results in pinker flowers. Panicle hydrangeas are less affected by soil pH and are generally adaptable to a variety of soil conditions.
For gardeners struggling to get hydrangeas to bloom, the first things to consider are the plant's type, location, pruning schedule, and exposure to winter weather. Understanding whether the plant blooms on old or new wood is important. With the right variety in the right location—and pruning done at the right time—hydrangeas are much more likely to reward the gardener with the flowers that make them so appealing.
Related Videos:
Understanding Why Hydrangeas Fail to Bloom
Common Hydrangeas
How do I keep my Annabelle hydrangea from flopping on the ground?
Why is my hydrangea not blooming?
When should I prune my Hydrangea Paniculata?
Related Resources:
Hydrangea paniculata
Hydrangeas
Pruning hydrangeas for best bloom
Many of the traditional hydrangeas grown in gardens, particularly bigleaf hydrangeas, produce their flowers on old wood. That means the buds for next year's flowers are already developing on the plant before winter arrives. Unfortunately, those buds can be especially vulnerable to the unpredictable temperature swings that occur during winter and early spring.
An early freeze can damage stems before the plant has fully entered dormancy. Just as troublesome are warm spells during winter. When temperatures rise, sap can begin moving through the stems, and as the plant tries to come out of dormancy, flower buds can begin to swell. If a freeze follows, the delicate flower tissue inside those buds can be killed.
In some cases, the stems themselves are killed back to the ground. In others, the stems survive but the flower buds are destroyed. The plant then leafs out normally in spring, making it appear healthy, but produces few or no flowers.
Location Can Protect Blooms
Because temperature fluctuations are such an important factor, where a hydrangea is planted can make a major difference. In areas with unpredictable winter temperatures, a protected location is preferable.
The north side of a house or the shade of a tree can help keep the soil cooler during winter and early spring. The cooler soil will hopefully delay bud development until after the hard freezes are past, reducing the chance that a sudden freeze will damage emerging buds.
Protection from early-morning sun is also helpful. If a flower bud has frozen overnight, rapid warming from the morning sun can cause additional damage.
A thick layer of mulch can provide another layer of protection. About four inches of mulch helps moderate soil temperature and can keep the ground from warming too quickly in late winter. Cypress mulch is one option because its lighter color reflects more heat than darker mulches.
Prune According to the Type of Hydrangea
Pruning is another common reason hydrangeas fail to bloom. The important question is whether the plant produces flowers on old wood or new wood.
Bigleaf hydrangeas, including the familiar mophead types with large pink or blue flower heads, generally bloom on old wood. Their flower buds are already present on the stems in late summer and fall, so pruning late in the season can remove the flowers that would have appeared the following season.
The best time to prune these hydrangeas is immediately after flowering, as the blooms begin to fade. Rather than shearing the entire plant, remove about one-third of the oldest canes at ground level. This encourages new growth while giving those new stems plenty of time to mature before winter.
Panicle hydrangeas, such as ‘Limelight,’ are different. They bloom on new wood, so they can be pruned in late winter. While they don’t need to be pruned every year, cutting them back to roughly 12 to 15 inches in late winter can produce vigorous new growth and larger flower heads. These hydrangeas are also more tolerant of full sun and generally have fewer problems with leaf diseases.
Managing Leaf Diseases
Hydrangea leaves commonly develop spots during the summer. Warm, wet conditions and prolonged periods of wet foliage can contribute to these diseases. Overhead irrigation can make the problem worse, so when watering is necessary, doing it early in the morning gives the foliage time to dry.
For plants with a history of serious leaf-spot problems, fungicides can provide additional protection. However, a few scattered spots are a cosmetic problem rather than a serious threat. If a large portion of the green tissue is lost, the disease can begin to affect the plant's overall health by reducing its ability to produce energy for the root system and next year's growth and flowers.
Soil and Flower Color
Soil pH is particularly important when growing bigleaf hydrangeas if flower color is a consideration. More acidic soil, around pH 5, tends to produce blue flowers, while a pH closer to 6 to 7 generally results in pinker flowers. Panicle hydrangeas are less affected by soil pH and are generally adaptable to a variety of soil conditions.
For gardeners struggling to get hydrangeas to bloom, the first things to consider are the plant's type, location, pruning schedule, and exposure to winter weather. Understanding whether the plant blooms on old or new wood is important. With the right variety in the right location—and pruning done at the right time—hydrangeas are much more likely to reward the gardener with the flowers that make them so appealing.
Related Videos:
Understanding Why Hydrangeas Fail to Bloom
Common Hydrangeas
How do I keep my Annabelle hydrangea from flopping on the ground?
Why is my hydrangea not blooming?
When should I prune my Hydrangea Paniculata?
Related Resources:
Hydrangea paniculata
Hydrangeas
Pruning hydrangeas for best bloom