How to prune hydrangeas

Asked October 9, 2017, 12:46 PM EDT

We have a very tall one several years old and 2 smaller ones, about 4 ft. I'm confused about how and how much to prune. There seems to be contradictory information in various online sources. I read one place to only cut old stalks, but some have old at the bottom and green at the top. Photos attached-flowers all faded now and I cut them off. Can you help? Thank you.

Multnomah County Oregon

5 Responses

Thanks for your question about pruning your hydrangeas. They both appear to be Hydrangea macrophylla, often called mop tops. Here is what the OSU Extension hydrangea expert says about pruning:

"Pruning - When to prune is mostly a matter of convenience. We have pruned both in the fall and early spring and had good results either way. It does seem that the later and the more harshly you prune that fewer flower blooms can be expected the next season. This is because most hydrangeas bloom on "old" wood. With young plants, be sure to prune enough growth to form them into a good "shape” and no more. The Paniculata and Arborescens varieties bloom on new wood so you may cut them for size in the spring or fall."

You can read more about hydrangeas and pruning advice using the link to the article, above. Hope this is helpful. Good luck!

Thanks Kristena. So the biggest one has 2 or 3 green stalks coming from the bottom of the plant but the rest are the old wood looking stalks. It almost sounds like I shouldn't prune at all? And the 2 smaller ones also have a lot of old wood now too. Then I read this from your handout:

Established hydrangeas tend to have branches that die back every year. These are completely woody branches inside the hydrangea. Cut up to a dozen of these branches down to the ground to spur new growth at the base.
(I have lots of thick wooden stalks. But they all have green at the top, leaves and formerly flowers. So should I cut them out or not? If they bloom on "old wood" how does that work for the new blooms? I'm more confused.)

You may prune in the fall after blooming or in the spring after the hard frosts are over. Remember, the later you prune and the more drastically you prune, the fewer blooms you’ll have. Prune to the first leaf node of this year’s growth. (does this mean the leaf at the end of the stalk or the one closer to the bottom? If it's the top I'd barely take anything off. If the bottom most of the stalk would be gone)Cut ½” to 1” above a budding node at a 45 degree angle. These buds will be the new leaves and blooms of your hydrangea. If you live in an area that is prone to spring frost, protect these buds with bed sheets or frost cloth (a light felt) on nights that frost is expected.

Part of the confusion is that many articles (including these) tend to mix (and confuse) various types of hydrangea. So, I have a suggestion: watch this Youtube created by a gardener in Aurora, OR (so we're talking about the same geographical area) and it's relevant only for H. macrophylla (which are the only ones in your pictures.) I think she is clear, explains the terminology, and you can actually see it happening!

Thanks Kristena, I will check out the video. I LOVE Youtube! I learn so much there. I didn't think to search there. Best, Wendy

Let me know if you still have questions, Wendy!