Why is my Hydrangea not blooming?
By Katherine Smith, CMG
There are three main reasons for a hydrangea not to bloom. The two most common reasons are too much shade and improper pruning. A third reason is weather damage to flower buds.
If your hydrangea has bloomed well in previous years and is not blooming this year, you should check its location. Over the years the shade/sun conditions likely have changed. Your hydrangea plant most likely started out in part shade; however, over time the plants and trees in the surrounding area have grown and reduced the amount of light to the plant. With this being the case, you may want to move your plant to a less shady location.
By Katherine Smith, CMG
There are three main reasons for a hydrangea not to bloom. The two most common reasons are too much shade and improper pruning. A third reason is weather damage to flower buds.
If your hydrangea has bloomed well in previous years and is not blooming this year, you should check its location. Over the years the shade/sun conditions likely have changed. Your hydrangea plant most likely started out in part shade; however, over time the plants and trees in the surrounding area have grown and reduced the amount of light to the plant. With this being the case, you may want to move your plant to a less shady location.
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When did you prune your hydrangea? You will need to know the variety of hydrangea in question. More than likely you pruned the plant at the wrong time; if so, you removed the potential flower buds. Your plant may be a variety that blooms on the previous year’s growth. The big leaf (H. macrophylla - Figure 1) hydrangeas bloom on the previous year’s growth (old wood) and should be pruned just after flowering and no later than the end of July as the new buds have already begun to form. The oakleaf hydrangea (H. quercifolia) and Japanese Mountain Hydrangea (H. serrata) also bloom on “old wood” and should be pruned as the big leaf (H. macrophylla).
There is always an exception to the rule. The new “reblooming” (remontant) types of hydrangea are able to form flower buds on new growth, and in doing so break the rule listed above. An example of the “remontant” type of hydrangea is: Invincibelle® Spirit. The panicle (H. paniculata) and smooth hydrangea (H. arborscens - Figure 2) bloom on the present year’s growth and should be pruned in late winter or early spring before the flower buds appear. 
Figure 2: Smooth Hydrangea: H.aborescens - USNA/ USDA
Most of us know our Tennessee weather often produces early fall freezes, low winter temperatures, and late spring freezes, all of which take a toll on hydrangeas. The big leaf hydrangea (H. macrophylla) is most affected by these weather conditions. Branches that have buds may be lost. A plant that looses the above ground part of its growth will emerge in the spring but will not have flowers until the next year.
A good rule to remember about hydrangeas is plant them where there will not be competition for space. This will result in a beautiful plant during its blooming season. By not pruning, you will have plant-dried blossoms for winter interest. Another rule to remember is to prune no more than one-third of the plant all the way to the ground. |
Figure 1: Big Leaf Hydrangea: H. macrophylla - USNA/ USDA
If you have the popular ‘Annabelle’ (H. arborescens) you may want to allow the stems to grow larger so they can support the heavy blooms. If you prune this hydrangea back by one-third, the plant will produce new growth resulting in more flowers. The panicled hydrangea (H. paniculata) can also be pruned in late winter or early spring. If you have the larger form of this type of hydrangea, you can train it to a tree form similar to training a crepe myrtle. Select the stems you wish to keep as trunks and remove the remainder of the stems. When the plant reaches the height you wish to maintain, the top can be trimmed resulting in a thickened canopy. 
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Your UT/TSU Extension can help you identify problems you are having with any plant. Take a specimen of your plant in question to your local UT/TSU Extension Office (in Rutherford County: 315 John R. Rice Blvd. – Ste. 101) where the Agents can positively identify the specific cause of your plant problem. Master Gardeners of Rutherford County will be happy to answer your garden-related questions here: Ask Us!
Sources:
USNA.USDA.gov/Gardens;
oilplantandpest.utk.edu/publications/ornamentalnwsltr;
UTextension.utk.edu/publications; UGAurbanag.com
Sources:
USNA.USDA.gov/Gardens;
oilplantandpest.utk.edu/publications/ornamentalnwsltr;
UTextension.utk.edu/publications; UGAurbanag.com
Posted: 7/31/2012
