Spring Clean Up Q&A: How to prune hydrangeas and when
/Q: Should I cut back my hydrangea plants now?
A: First of all, you are not going to kill your hydrangea if you cut it back or prune it at the wrong time, but you will lose the blooms that you would have had this garden season. So we want to be mindful about when we are pruning, so that we enjoy the maximum number of blooms.
Second, prune-time depends which hydrangea bush you have.
If you have Hydrangea macrophylla (also known as big leaf hydrangea or mophead hydrangeas) then don't cut them in the spring! They are a shrub (like lilacs) that you only want to "prune after bloom." They spent August and September setting buds on their stalks, so you don't want to cut them off or you won't get any flowers this year.
This is what Hydrangea macrophylla looks like now. Notice how it's a collection of upright stalks? That's how you identify it without any leaves or flowers.
Look closely and you will see each of the stalks are covered in buds!
So don't cut them down in the fall or in the early spring or you will lose your flowers. You can wait until later spring until they start leafing out to guide what you trim off to make a pleasant shape. (Also see what turns green and then you only want to trim off the dead wood, including any brown wood above the greening buds.)
Read more about Hydrangeas here.
If you have an 'Endless Summer' series hydrangea, then you can do no wrong, because this cultivar blooms on old and new wood, so it will flower no matter when you prune it.
If you have Hydrangea paniculata (Limelight, Pinky Winky, Quick Fire, etc.) also known as upright hydrangea, you can prune them now. Last summer, we had enough rain that these shrubs grew BIG, so the Victoria Gardens Landscaping Division is pruning these back hard this year.
Take off the spent flowers.
Eliminate crossing and rubbing branches.
Prune for size and shape.
Prune for air flow.
University of Minnesota Extension has a great article and demonstration video if you want to read more.
HYDRANGEA MARCROPHYLLA ‘FIRELIGHT’
‘LITTLE QUICK FIRE’ HYDRANGEA PANICULATA
Hydrangea paniculata