Hydrangea pruning! When is the best time? When is the correct time?
I promise to make this easy once and for all.
Hydrangeas are confusing, to say the least, but in this article, I am going to set the record straight and simplify your gardening life. For the most part, Hydrangeas fall into two categories.
Those that flower on new wood, and those that flower on old wood. Simple enough right? Not really. Then to make matters worse there are those that bloom on old wood and new wood.
The Nikko Blue Hydrangea is in the macrophylla family of hydrangeas and for the most part, but not always, Macrophylla Hydrangeas bloom on old wood. So what does that mean?
What is old wood and what is new wood? And should I care? No, I really don’t think you should care. It’s just too confusing to keep it all straight. But for the record, I’ll show you some old wood and some new wood and explain why the gardening community makes such a big deal out this.
Look to the bottom left of the above photo. See where I made the cut to remove this branch from the plant? I made my cut into old wood. Then if you follow along from where I made that cut over to the bottom right of the photo you’ll see where the new growth starts.
That’s the beginning of the new wood. Notice how it’s light green in color? It’s also softer and more pliable because it’s new growth from the current growing season. As the season progresses and we get closer to winter this new growth begins to harden off so it’s durable enough to withstand the winter weather.
I should note, just for the record, that I took this photo on July 2nd. The old wood that you see in the photo was from last years growing season. The new wood, of course, is from this year’s growing season. Why does it matter? I’m glad you asked.
Some hydrangeas, many in the macrophylla family, start producing flower buds this summer for the following year. So if you prune your hydrangea too severely late in the season you are likely to cut off many if not all of the flower buds for next year.
Same thing with Rhododendrons, Azaleas, and some other plants. So ideally you should prune them right after they bloom then leave them alone. However, with Hydrangeas, that’s not easy to do because the new varieties like Endless Summer can bloom well into the fall. Hmmmmm. That’s a problem.
Now lets talk about those other Hydrangeas. The ones that don’t bloom on old wood.
Members of the Hydrangea paniculata and Hydrangea arborescens families are Hydrangeas that bloom on new wood only. So what does that mean?
When these hydrangeas start growing in the spring they grow like crazy, putting on all kinds of new growth until early or mid-summer. Then the plant stops growing and immediately starts making flower buds right on the end of the new branches that it just produced.
In the above photo, you can see the new growth, then right at the end of that new growth, the flower bud is formed. Is that a good thing?
It is indeed because that means that no matter what kind of crazy pruning your spouse did to the plant last fall, this type of hydrangea is very forgiving and will bloom in spite of any excessive pruning it may have received.
No winter damage. This is a huge benefit because this type of hydrangea does not carry any flower buds into the winter that need to survive all the way through winter into summer of the following year.
That also means that a late frost that completely wipes out the plant in the mid to late spring will not hamper its ability to flower. As soon as the plant bounces back from that late frost damage it’s off to the races with new growth, then flowers.
The macrophylla hydrangeas are not that forgiving. If they receive heavy freeze or frost damage you might not see any blooms at all the following season. Or if you do, it will be near the end of the summer before you see them.
So all of these different scenarios make the “when do I prune my hydrangea” question really hard to answer.
Those that flower on new wood can be trimmed really hard in the fall or early spring and they’ll still bloom. Those that bloom on old wood really shouldn’t be pruned hard in the fall and not at all in the spring.
Still confused? Yeah, me too.
When I set out to write this article I thought this was going to be easy to explain. It’s not. It’s really, really confusing because now all of sudden we have new varieties of hydrangea that like to bloom on new wood and old wood.
So here it is. This is the answer in a nut shell.
If your hydrangeas need pruning, prune them right after they finish blooming. Doesn’t really matter what flavor they are. Prune them right after they bloom.
I noticed when trying to get these photos that even those that bloom on old wood send those blooms from deep within the plant. So unless you are cutting your plants back really hard, you should still leave plenty of flower buds for next year.
It’s really the only window of time that you have. If you wait any longer you are sure to cut off flower buds for next year.
Now, with that said. If you know for sure that your Hydrangea is from the paniculata or arborescens families of Hydrangeas you can prune really hard late in the fall or early in the spring and you’ll be fine.
But if you’re not sure, just get in the habit of pruning them right after they are done blooming.
Boy, I hope this helps.