Hydrangeas are widely coveted for their lovely blossoms. Twenty-three species of hydrangeas are recognized according to the United States National Arboretum. A few of the species readily bloom off new growth and rarely have difficulty producing blossoms each season, unless planted in an overly shady area or due to late-spring season pruning of the new growth. Bigleaf and oakleaf hydrangeas bloom off old growth and prove difficult to continue repeat flowering without care.
Prune oakleaf and bigleaf hydrangeas by only removing new growth in small sections in either the fall, winter or early spring. Oakleaf and bigleaf varieties blossom on the previous years' growth. If removal of all new growth is performed during pruning, then the shrub will only bloom every other year with any ratio of success and eventually may cease blooming altogether. Care must be made when pruning to only remove a little of the new growth each season to maintain shrub size, shape and airflow. Panicle and smooth hydrangeas flower only on new growth, so care must be taken in the early spring to only prune old growth and areas of dead branches to maintain yearly blooms.
Protect hydrangea varieties that flower on old growth shoots during periods of hard spring frost. The shrubs easily break dormancy and begin to produce buds in preparation for spring and summer, but a hard freeze will kill the buds and severely damage the plant--rendering it unable to blossom. Cover the plants during times of hard freeze using old blankets. Consider planting hydrangeas that blossom on old growth against buildings or fences to offer the plant added frost protection.
Refrain from fertilizing after pruning. Fertilizing a hydrangea will promote excessive foliage growth instead of blossoms.