Why aren't my hydrangeas blooming?
Written by
Michael Sullivan
Reviewed by
Prof. Martin Thorne, Ph.D.If you are like many gardeners, you have probably been disappointed when your hydrangeas don't bloom as expected in the summer months. Numerous typical problems may be responsible, such as not pruning your plant at the right time, inadequate sunlight, and a lack of nutrients. Knowing the causes can help you determine the best way to promote blooming for summer. I had a hard time getting my hydrangeas to bloom until I realized they weren't getting enough sunlight.
Pruning Errors
- Old-wood varieties lose buds if pruned during winter dormancy
- Pruning at incorrect times removes developing flower buds
- Always prune based on bloom wood type: old wood after flowering
Light Deficiency
- Less than 4 hours direct sun reduces flower production
- Morning sun with afternoon shade is the ideal light pattern
- Leggy growth indicates insufficient light exposure
Nutrient Imbalance
- Excess nitrogen promotes leaves at the expense of blooms
- Use balanced 10-10-10 fertilizer avoiding high-nitrogen formulas
- Soil testing reveals nutrient deficiencies affecting flowering
Environmental Stress
- Drought stress during bud formation prevents flowering
- Winter bud damage kills potential blooms in cold climates
- Extreme heat above 90°F (32°C) causes bud abortion
Timing for pruning affects flowering. Old wood bloomers are plants that set their buds in the late summer for the next year's bloom. Suppose you prune these types of hydrangea after August. In that case, you will eliminate the buds that are already developing. New wood bloomers set buds in the spring, so pruning in the winter encourages their growth. I plan the timing for pruning based on the bloom cycle for that type of hydrangea.
Sunlight needs differ slightly from one variety to another, but they all require a reasonable amount of light. Bigleaf hydrangeas prefer the morning sun, but not the hot afternoon sun. Panicle types can take full sun in cooler climates. If planting in an area where large trees will grow, stay aware of how new shade areas may affect exposure as the tree leafs out during the warmer months.
Effective nutrient management involves a soil test every two to three years. Too much nitrogen in the soil produces many leaves but few flowers. In early spring, apply 5-10-10 fertilizer or another fertilizer with a lower nitrogen content and higher phosphorus content. Do not apply fertilizer to encourage tender growth late in the season if your gardening location is prone to frost during winter, as the plant will be susceptible to frost injury.
Environmental Stewardship safeguards against bloom loss. Water deeply during the summer drought, especially during bud formation. Install windbreaks for exposed plants. When possible, mulch the soil with three inches of bark to help retain moisture. Protect your plants from late frosts when buds have swollen with fabric covers.
Recovery can take time following the resolution of problems. Hydrangeas may require an entire season to produce new buds if pruning mistakes are made. Be patient with plants as they recover from winter damage. I relocated my oakleaf hydrangea, which then took 2 years to flower completely, but now it is blooming abundantly.
Read the full article: How to Care for Hydrangea: Complete Growing Guide
