Weekend Gardening: Gardenias And Hydrangeas

June 25, 2011

theresafriday.jpgHydrangeas and gardenias are two of our most beloved shrubs in the South. They are revered for their flowers and are planted in large drifts throughout Northwest Florida.

Gardenia shrubs are evergreen and produce shiny, dark green leaves. They are known for their waxy, creamy white flowers. The flower’s aroma, adored by many gardeners, is powerful and pleasant.

Hydrangeas are deciduous shrubs and produce coarse, light green leaves. Their large leaves will fall off after a freeze. Although you are left with bare sticks during the winter, the summer blooms are well worth the winter bareness. While there are many different types of hydrangeas, the mopheads are probably the most recognizable. Their large inflorescences are usually blue on acid soil, pink on alkaline soil and a dirty white on neutral pH soil.

Even though these shrubs are different in many aspects, the one thing they have in common is when they “set” their flower buds. Both shrubs develop flower buds on old (mature) wood of the previous year and open in early summer of the following year. Flower buds are formed at the terminal end of stems and, if not killed by cold or removed by inappropriate pruning, provide the showy floral display the next year.

The best time to prune gardenias and hydrangeas is after they finish flowering for the season. Pruning them at the incorrect time of the year, such as winter, will remove the flower buds.

Your pruning program should be purposeful. First, remove all diseased, weak and dead wood. It will be important to disinfect your pruning equipment after removing suspect branches. Pruning shears, loppers and saws can be dipped in a weak bleach solution to prevent spread of disease between plants.

Once all the problem branches have been removed, then think about thinning the plant. Shrubs are often thinned to reduce a top-heavy appearance or to open up a dense canopy. To thin, simply remove some of the oldest branches by pruning them down to the ground. Remove about a quarter to a third of the branches, selecting the oldest ones for elimination. When thinning, take care not to damage the nearby younger stems and foliage.

Next, cut back branches that are excessively long. Prune back to a lateral branch that is six to twelve inches below the desirable plant height, removing no more than a third of the stem. Cut each branch separately to different lengths with hand pruners. This will maintain a neat informal shrub with a natural shape. Plants sheared into various geometric shapes produce a formality not suitable for many modern, natural landscapes. Making pruning cuts down inside the canopy instead of on the outside edge will also hide unsightly pruning cuts.

Within the last several years, reflowering hydrangeas have found their way into the marketplace. Reflowering hydrangeas produce an initial flush of flowers followed by sporadic flowering or later flushes of flowers in the same growing season.

Endless Summer® Hydrangea is a reflowering hydrangea. It is very forgiving and will not suffer if left unpruned or pruned at the wrong time. In fact, young, recently planted shrubs are best left alone. Unlike other hydrangeas, your Endless Summer® will bloom on both old and new wood, branches that grew last year and the new branches from this year. Another unique feature is that this hydrangea will continue to set buds and bloom throughout the season. Deadheading, or removing the spent flowers will encourage continual blooming.

For more information, contact Theresa Friday at 850-623-3868 or email tlfriday@ufl.edu. Friday is the Residential Horticulture Extension Agent for Santa Rosa County.

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