Pruning Your Old Wood Hydrangeas

Old wood flowering hydrangea that should be examined now

Pruning your old wood hydrangeas may be possible now. But not all of them which is a source of much confusion.Which ones should you examine for this task?

Your old wood plants include big leaf hydrangeas (macrophylla), mountain hydrangeas (serrata), oak leaf hydrangeas (quercifolia),  and climbing hydrangeas (petiolaris). Even if your plant is a rebloomer like Endless Summer it retains old wood flower power and buds can be there that formed on last year’s growth.

The only ones you have a green light to take care of now are purely old wood bloomers like oak leaf hydrangeas, climbing hydrangeas, non-reblooming big leaf hydrangeas, and non-reblooming mountain hydrangeas. You can work on the obvious stuff like deadheading to neaten up the plant. Cut that spent flower down to the first set of live buds.

PRUNING YOUR OLD WOOD HYDRANGEAS: WHAT TO CUT

In order to prune your old wood hydrangeas, you first inspect your plants for the 3Ds (dead, damaged, diseased wood). Carefully remove them, ideally at ground level with a lopper depending on the issue. Don‘t forget to cut inward growing branches, pencil-thin stems, and any stems that are rubbing.

If you find some old canes that look like this one with peeling bark, or this pebbly one

Old hydrangea canes that need to be removed

cut them at ground level. They won’t produce a flower ever again.

And if your plant has a lot of old stubs at the base from prior year’s cuts like the one in this photo,  

Big leaf hydrangea shows stubs of old cuts clogging up the base that need to be removed

eliminate those stubs to unclog the trunk. You’ll improve air flow and deprive slugs of hiding places while they lay in wait to nip on your plant.

If you’re not sure if your stem is alive, scratch it with your fingernail. If it shows green, it’s a live stem.

Hydrangea stems that are alive show green beneath the bark.

WHAT TO DO WITH WAYWARD STEMS WHEN PRUNING OLD HYDRANGEAS

Wayward stems might be present at the base of your plant. Now is the moment to get rid of them. But be cautious since they may have been low enough to develop roots, which will give you a new plant. If you tug on them and find roots, snip them off from the mother plant. Pot them up for a few weeks before setting them out in the garden for their next life. A little TLC and encouraging fertilizer while they are in pots will get them off to an excellent start. Cool, huh?

Low lying stems easily root when they are in contact with the ground for a few weeks.

PRUNING OLD WOOD HYDRANGEAS THAT REBLOOM

For your big leaf or mountain hydrangeas that are rebloomers, you can freely get rid of the stems that have already rebloomed. They won’t provide any more flowers for you. They look like this, with flower stems coming off the sides:

Spent stem from a reblooming hydrangea that should be cut now.

You will be tempted to deadhead your rebloomers. Do not do that until you are well past your frost free date. When you cut the tips of your rebloomers, you release the hormones in the stem which will “wake up” the sleeping flowers along its length. Once those sleeping buds break dormancy, they are susceptible to being killed by late season frosts and in one cold snap, you can kiss your second round of flowers goodbye.

Once the flower buds appear on your plant (they look like little broccoli heads), you can cut anything that demands it. Deadheading when you see “broccoli” is a perfect idea as that tip cutting will release the growth hormones in the stem.

TECHNIQUES FOR PRUNING OLD WOOD HYDRANGEAS

OK. Now that you know all this, it’s time to get outside and prune those plants. Tick-Tock!

Use your loppers to take stems off as close to the ground as possible. Here’s where you must be extremely careful not to dislodge the new buds/leaves that you see at the base of your plant. Some of them might be the start of new stems that will generate flowers at the tips before the season ends. If you can’t get to that stem now, mark it with a twistie or pipe cleaner for removal in the fall when the coast is clear. Or cut it a few inches from the ground; it can come out altogether at a later date.

You can also remove the pebbly stems and those with peeling bark. Cut as close to the ground as you can get without endangering any new spring growth.

PRUNING OLD WOOD HYDRANGEAS: OAK LEAF AND CLIMBING 

It’s unlikely that your oak leaf and climbing hydrangeas will need any pruning before they flower. Look them over for the 3Ds, inward growing, rubbing, and pencil-thin stems. Take those out. You might have a low-lying branch or two on your oakleaf that you can designate for later removal. You can delay action until it gives you its magnificent flower this season. Wrap a twistie or pipe cleaner at the base of that stem so you know where to cut later on.

And if your climbing hydrangea needs a haircut badly as mine does, wait until it flowers before you do that. Mine has buds on it so I know I’m in for a treat in a couple of months. Only after that bloom cycle will I take the pruners to it.

PRUNING AFTERCARE

There is pruning aftercare to do now. First up is fertilizing with a granular rose fertilizer or shrub fertilizer. No 10-10-10. No plant uses nutrients in equal amounts. Applying products like 10-10-10 just contributes to run-off and pollution issues. Follow the directions on the label. Second, check your irrigation if you have it, and, third, finish with mulch. It can be compost, leaves, bark, etc. And of course, disinfect/sharpen your tools. You don’t want to transfer any pathogens to the next plant you work on, and your pruners need to be razor sharp for that next plant.

PRUNING PANICLE HYDRANGEAS ONE MORE TIME

Since I wrote about pruning new wood bloomers last time, I have found a terrific video for pruning panicle hydrangeas (hydrangea paniculata). It uses ‘Limelight’ as the model. The principles apply to all panicle hydrangeas. https://youtu.be/vd3AuBso30U.

IDEAS FOR MOTHER’S DAY

A reminder: Mother’s Day is less than 2 weeks away. If you want to gift someone with a signed copy of my hydrangea book, you still have time to do that. In fact, you have two options. One is to order from my site by going HERE. I will inscribe your book upon request.

Or you can come to Sam Bridge Nursery in Greenwich, CT this Saturday (May 4) where I’ll be giving 2 presentations and selling/signing my book. Here’s the info:
Sam Bridge Nursery & Greenhouses, 437 North Street Greenwich, CT 06830
Topic: Blooming Hydrangeas, 11 a.m., Free, https://sambridge.com/events/
Topic: Shrubs, The New Perennial, 1.30 p.m. Free, https://sambridge.com/events/