Hydrangeas brighten up the summer garden with their lacy blooms. If your hydrangea is not flowering, the United States National Arboretum points to three possible culprits. Too much shade and improper pruning can affect all hydrangeas, while weather-related damage to flower buds affects the bigleaf hydrangea, according to the USNA.
Plant your hydrangea in an area that receives some sun. Hydrangeas in general prefer light shade, but too much will keep the shrub from flowering. The panicle hydrangea is one species that grows best in full sun, according to the USNA. If your shrub is producing sparse blooms, consider moving it to a brighter location or trimming any trees overhead.
Prune your hydrangeas in the summer. Because they bloom on the previous year's growth, pruning in fall, winter or spring would remove potential flower buds, the USNA says. Cut back some of the old and new weaker shoots from the plant's base, but do not to cut it back to the ground, according to Texas Cooperative Extension.
Protect your bigleaf hydrangea from unfavorable weather as best you can. An early fall freeze or late spring freeze can reduce flowering, the USNA says. Spread a light sheet over the top of your plant to shield it from unexpected frost.