Weekend Gardening: Distinctly Southern Hydrangeas

July 26, 2014

by Santa Rosa County Extension

Nothing defines a southern landscape more than hydrangeas.

These beautiful, large flowering shrubs fill gardens with their green, leafy foliage and incredible blooms during the warm months.

In order to ensure consistent and reliable blooms, these shrubs must be cared for correctly. In addition to proper site location, fertilizer and moisture conditions, hydrangeas may require pruning. Proper pruning includes correct timing.

Hydrangea aficionados are constantly debating pruning techniques. There are many different types of hydrangeas and pruning differs according to the type. It is a big genus of plants and so it’s important to know what type of hydrangeas you may have and on what type of wood they bloom on.


Blooms on old wood, prune after flowering

The bigleaf hydrangeas, known scientifically as Hydrangea macrophylla, are what most people think of when you mention hydrangeas. Most gardeners will know these as mopheads (also called hortensias) and lacecaps. Many of these blooms will be blue or pink although other colors now are available.

Many large colonies of bigleaf hydrangeas have existed around old homes for decades, surviving and blooming in spite of neglect.  This tells us that it is not necessary to prune bigleaf hydrangeas.

However, if you want to keep these shrubs within a defined boundary, control their height or rejuvenate old shrubs, it will be necessary to prune them.

Bigleaf hydrangeas can be reduced in size immediately after flowering.  A general rule of thumb is that you may remove up to a third of the shrub’s height.  Be sure to complete your pruning before August.  This is critical because next year flower blooms start to form in August.  Pruning after August will remove next year’s blooms.

There now is a small group of bigleaf hydrangeas that are everblooming or remontant.  Endless Summer® is one well-known brand.  According to the developers of these reblooming hydrangeas, remove spent flowers to encourage rebloom.  They are quite forgiving and will not suffer if left unpruned or pruned at the wrong time because these cultivars bloom on both old and new growth.

Our native oakleaf hydrangea (Hydrangea quercifolia) is a large, deciduous shrub that can grow up to six feet tall.  It has deeply lobed, oak-like leaves which turn bronze in the fall.   This plant does not usually need pruning. If reshaping or size-reduction is necessary, prune after blooms begin to fade.

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Lacecap hydrangea

Blooms on new wood, prune in early spring

Smooth hydrangea (H. arborescens) is the other U.S. native. The most common cultivar, ‘Annabelle’, produces rounded inflorescences that may reach up to a foot in diameter.

The panicle hydrangea (H. paniculata) is more of an upright type.  It is typically a 10 to 15-foot large shrub or low-branched tree.

Panicle and smooth hydrangeas flower on current year’s growth and can be pruned anytime from late summer until early spring. If pruning these two species in the spring, try to prune before leaves appear.

Winter pruning

Established bigleaf, panicle, oakleaf and smooth hydrangea plants can often benefit from rejuvenation pruning. Remove about one-third of the oldest stems each year.  The result is a fuller, healthier plant. This type of pruning is easiest to do in winter, since the absence of leaves makes it easier to see and reach inside plants.

Hydrangeas offer a wide variety of plants which can make the timing of pruning difficult to remember.  Just keep in mind, if in doubt, either don’t prune at all or prune after flowering.

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Written by William Reynolds · Filed Under FEATURE TOP STORY, Features, News