Weekend Gardening: Distinctly Southern Hydrangeas

July 28, 2018

by UF/IFAS 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.

Comments

7 Responses to “Weekend Gardening: Distinctly Southern Hydrangeas”

  1. Lynne on July 28th, 2018 10:39 pm

    My hydrangeas bloomed last year—the second year I have had them. The first year, they were in bloom when I bought them. This year they are very lush and healthy but have no blooms. Not knowing whether they bloom on old wood or new wood, I did not prune them in August last year but did ithisvspring. Because they did not bloom, should I assume they bloom on old wood and prune them in August?

  2. Linwood West on July 28th, 2018 5:14 pm

    How do I make my hydrangea blue?

  3. Liz Meyer on July 28th, 2018 4:02 pm

    I have the common blue and live in Western NC. We had snow in March and April. I couldn’t prune until May. I fertilized twice and had to leave for all of June. When i returned they had “bushed out” and had a few large blooms close to the porch. Suggestions for pruning this year? This was my first year with them as they were blooming when I first moved in June 2017.

  4. Paulette Copley on July 28th, 2018 1:54 pm

    I live in Polk County Florida. Is it possible to grow hydrangea ’s in my area? If so, which one would grow the best? I of course have sand as the planting base. Would it be best to build up the soil?

  5. anne1of2 on July 28th, 2018 1:22 pm

    Just seeing these flowers makes one feel cooler. Great as a shrub. Great as bouquet in the house. Great moral booster! Take some to a friend.

  6. Mina Black on July 28th, 2018 1:19 pm

    I leave in Gilbert Az. Can I grow hydrangeas in the hot climate 9 and 10? If yes what are some names. Thank you so much.

  7. Lena Nusz on July 28th, 2018 12:52 pm

    Planted 2 hydrangea this summer have brown spots on leaves but are blooming great they are blue and pink please tell me what wrong with them

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