TIME TO PRUNE YOUR HYDRANGEAS, YES AND NO
Time to prune your hydrangeas, but not all of them. Pruning hydrangeas is one of the hardest things for gardeners to grasp since it varies by species and it’s not a once a year thing.
This time around, the subject is hydrangeas that flower on old wood: big leaf (hydrangea macrophylla), mountain (hydrangea serrata), oak leaf (hydrangea quercifolia), and climbing (hydrangea petiolaris). They all bloom on flowers that were produced on last year’s growth. Some big leaf and mountain hydrangeas can also flower on stems that will grow this year (rebloomers). More on that in future posts.
TOOLS TO PRUNE BIG LEAF HYDRANGEAS
Before you even start to prune your hydrangeas, however, make sure you have the right tools including some kind of disinfectant. You don’t want to unknowingly spread disease as you move from plant to plant. A simple spray of rubbing alcohol (70%) from the drugstore is all you need to spray on your tools to protect your plants.
KNOW THE BASIC PRUNING RULES
Basic pruning rules apply to all hydrangeas. Take care of the 3Ds: dead, diseased, and damaged wood. It has to go. Next remove any stems that are crossing and growing inward.
WHAT TO PRUNE ON OLD WOOD ONLY HYDRANGEAS
Once that is done, you can do the real pruning at hand. For your oak leaf, climbing and big leaf hydrangeas that flower on old wood like Nikko Blue, City Line® and ‘Lady in Red’, you can cut out dead growth at the base and unclog it to improve circulation. You can also do some deadheading. Cut off the dead flowers down to the first set of live new growth. DO NOT DEADHEAD YOUR REBLOOMERS. The same applies to your mountain hydrangeas like ‘Blue Billow’, and ‘Preziosa’. You’ll have another chance at your rebloomers when you see “broccoli” – those tiny little heads that will become flowers.
HOW TO TELL IF YOUR PLANT IS A REBLOOMER
Don’t know if you have a rebloomer? Look for stems that had multiple flowers coming off them like the one in this photo which is now finished/spent and dead.
WHAT DO OTHER DEAD STEMS LOOK LIKE?
What does a normal dead stem look like? Take a look at the stems in the two photos below: the one on the left was very crusty and scaly – probably about 3 years old. The center was pure white with no green in it, a sure sign it was dead. The other wasn’t quite so old, but bleached white nonetheless. They got cut to the ground which opened up the plant and stimulates it to make more stems which means more flowers.
If you’re not sure if a stem is dead, scratch it with your fingernail and look for that telltale green. If you don’t see it, it’s dead. Sometimes just the tip of the stem has been killed by the winter so start at the top and scratch your way down.
WHEN TO PRUNE OLD WOOD ONLY BIG LEAF AND MOUNTAIN HYDRANGEAS
Don’t wait too long to do this pruning on your big leaf and mountain hydrangeas. If your plant is already pushing new growth with green buds at the base, you can slip and cut off a bud or two – Whoops!- and lose some of your new growth. So be very careful of both tips and the base of your plant with your pruners and cutters.
WHEN TO PRUNE OTHER OLD WOOD HYDRANGEAS
For your oak leaf and climbing hydrangeas, deadheading and unclogging the base are the order of the day. Also remove any dead, diseased and damaged stems you can identify. Neither species rebloom.
DO SOME OTHER MAINTENANCE NOW
This would be a good time to fertilize, check your irrigation if you have any, and remulch your plants once you have finished pruning them. I have devoted full chapters in my Success With Hydrangeas book to these topics. Each treatment is critically important for the best performance of this plant.
PRUNING YOUR NEW WOOD HYDRANGEAS
Next time I’ll talk about pruning your woodland hydrangeas like ‘Annabelle’ and panicle hydrangeas like ‘Limelight’. I’ll also write more about pruning rebloomers as the calendar moves along and about hydrangea pruning in general. In the meantime, enjoy watching spring emerge.
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