hydrangea pruning #385160 - Ask Extension


hydrangea pruning #385160

Asked February 14, 2017, 4:06 PM EST

When should a hydrangea be pruned? I had the belief that it was in the late winter, however, mine are beginning to show buds with the unseasonably warm weather. Also, what can be done to get a hydrangea to bloom that hasn't in 10 years?

Montgomery County Maryland

Expert Response

We assume you have mophead hydrangeas (the kind with the big flowerheads in blue or pink.)  These shrubs have a different pruning schedule than most summer-blooming shrubs.  The buds you see were formed last summer.  They are swelling up now, which is why you may be noticing them.

Most summer-blooming shrubs are pruned in late winter-early spring, and they can produce flower buds on the new wood that grows after the pruning.  No so for mophead hydrangeas.  

Mophead hydrangeas produce their next summer's flower buds the year before in late summer after blooming.  The buds wait all winter and bloom the following summer.  This means they are blooming on "old" not "new" wood.  

 If you prune your hydrangeas in the late winter, you are cutting off all the flower buds and thus this would explain why your hydrangeas are not bloomsing for you.  (They also will not bloom if all the buds are killed by very low winter temperatures, or if they are growing in a too-shady site.)

So, these hydrangeas do not have a good pruning time.  If you must prune to control size, prune immediately after flowering (when flower color starts to change) or just realize that spring pruning will remove flower buds.  Avoid pruning if you can.  A too-large hydrangea can also be removed or replaced. 

There are new varieties of mophead hydrangeas that bloom on new wood. That avoids the pruning time issue.  


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