Pinch Prune Your Hydrangeas

Just when you thought you were finished w/pruning your hydrangeas, now I tell you it’s time to “pinch prune” them. But wait – someone said I’m not supposed to cut them at all! Yes and no.

WHEN DO HYDRANGEAS SET UP THEIR BUDS

Big leaf hydrangeas (macrophylla) and mountain hydrangeas (serrata) set their flower buds under two conditions: on short day length (after June 21 in the northern hemisphere) and when night temperatures are consistently below 60 degrees. The same goes for oak leaf (quercifolia) and climbing (petiolaris) hydrangeas. From that science we get our general rule of thumb: don’t prune/cut these plants after about August 1 unless you’re prepared to risk cutting off next season’s flowers.

WHY PINCH PRUNE HYDRANGEAS IN MID SEASON

Why then should you think about cutting them now? Simply stated, if you cut some of your newly grown stems now before August 1, you can accomplish two objectives: first, you stimulate that stem to branch into two more stems, optimally giving you a chance at two flowers at the tip next year instead of one (Mother Nature needs to give us a benign winter, of course). Second, you get a better view of this season’s flowers which are somewhat obscured by the newly produced stems.

Big leaf hydrangeas can grow too big to see their flowers.

HOW TO PINCH PRUNE HYDRANGEAS IN MID SEASON

Here’s what you do. Step back and assess which of your plants’ new growth is hiding this year’s flowers and decide which stems you would like to cut. Make those cuts just above the place on the stem where the leaves meet it and where you see the growth of new stems emerging from it. That’s the sweet spot.

This is where you should cut the stem to “pinch prune” your hydrangea.

This is how you “pinch prune” your hydrangea.

If you can’t decide which stems to cut, go after those with leaf spots on them. You should be destroying them anyway as the spores of the fungus that causes those spots will continually plague your plant and reinfect it. I discuss insects and diseases in my book to give you a heads-up on what to look for and what to do.

WHAT TO DO WITH THE CUTTINGS

If you are into making more plants, you can take the stems that you cut and propagate them. Voila! Free plants for a little easy work. Hydrangeas propagate very easily and I devote an entire chapter to it in my book.

WHAT HAPPENS WHEN YOU PINCH PRUNE

When you cut these stems, you are forcing the growth hormones from the stem that you cut into those two new stems. They will grow out to form flowers at their tips on the short day lengths and consistently cool nights that are come after August 1. So instead of getting one flower at the tip, you now can get two. In some parts of the country, however, those night temps won’t consistently be at 60 degrees or lower by August 1 so you have a little wiggle room, but don’t wait too long. The weather is something over which you have little control.

DON’T BE AFRAID TO TRY THIS TECHNIQUE

If you haven’t done this before, consider pinch pruning hydrangeas as an experiment. Don’t cut all the new stems — just a few.

Hydrangea after being “pinch pruned.” Not all new stems have been cut.

It’s up to you. If the winter weather cooperates, your pinch pruning will be a wild success and you’ll be awash in flowers next June. And you will have learned another new pruning skill.

Here’s to happy hydrangeas, not a myth but a reality!