Why Are My Hydrangeas Not Fully Blooming?
Hydrangeas (Hydrangea spp.) are popular shrubs that are grown primarily for their showy flower clusters. Most hydrangeas don't produce flowers in their first season. However, established hydrangeas not blooming can be the result of improper pruning or fertilization, freezing temperatures or lack of sunlight.
Species of Hydrangeas
The hydrangea species with which most gardeners are familiar is the bigleaf hydrangea (Hydrangea macrophylla, zones 5 to 11), which produces round clusters of flowers that may be pink or blue depending on the pH of the soil.
The oakleaf hydrangea (Hydrangea quercifolia, zones 5 to 8), which gets its name from its foliage that resembles that of oak trees, produces flower clusters in a pyramidal shape.
Other species of hydrangeas include the panicle hydrangea (Hydrangea paniculata, zones 3 to 8), which produces cone-shaped clusters of fragrant white flowers, and the smooth hydrangea (Hydrangea arborescens, zones 3 to 9), which has small white flowers arranged in flattened clusters, or corymbs.
Why Don't My Hydrangeas Bloom?
"My hydrangeas are not blooming" is a complaint that home gardeners often make. Let's look at some of the reasons this happens.
Some hydrangeas, including the popular bigleaf hydrangea and the oakleaf hydrangea, produce their flowers from buds that appear on the previous growing season's wood.
These hydrangeas should be pruned immediately after they are finished flowering. If you wait until fall or winter to prune these hydrangeas, you risk removing flower buds and may end up with few or no blooms in the spring.
Other hydrangeas, such as the panicle hydrangea, produce their flowers on new wood from the current growing season. These species are best pruned in the fall and winter and can be pruned more harshly.
Lack of Water or Sunlight
Hydrangeas are known for being shade-loving plants. But while some shade is important, too much of it can result in poor or incomplete flowering. Morning sun and afternoon shade are ideal for many types of hydrangeas, including the bigleaf hydrangea.
As a rule, the more sunlight a hydrangea plant needs, the more water it requires. Lack of watering can have a negative effect on blooming.
Overfeeding hydrangeas with fertilizer rich in nitrogen can result in fewer blooms. This is because nitrogen stimulates leaf growth rather than flowering. To encourage bloom production, hydrangeas should be fertilized with formulas that contain more phosphorus.
Cold Injury in Hydrangeas
The reason behind a hydrangea not blooming can be due to factors out of your control, namely temperatures.
The buds of many hydrangea species are sensitive to frosts and cold temperatures. In the case of hydrangeas that produce flowers on old wood, low winter temperatures can damage buds, resulting in few blooms in the spring. Late freezes in spring can also kill buds and reduce blooming.
In colder climates, you can protect hydrangea plants and their precious buds during the winter months by surrounding the plants with chicken wire and filling up the space around the plants with leaves. Choosing cultivars that are reliably winter hardy where you live can minimize this problem.
- University of Minnesota Extension: Pruning Hydrangeas for Best Bloom
- Clemson Cooperative Extension: Hydrangea
- University of Massachusetts Amherst: Why Hydranagea macrophylla Don’t Flower
- Missouri Botanical Garden: Hydrangea macrophylla
- Missouri Botanical Garden: Hydrangea paniculata
- Missouri Botanical Garden: Hydrangea arborescens
- Missouri Botanical Garden: Hydrangea quercifolia
Since beginning her career as a professional journalist in 2007, Nathalie Alonso has covered a myriad of topics, including arts, culture and travel, for newspapers and magazines in New York City. She holds a B.A. in American Studies from Columbia University and lives in Queens with her two cats.