The Best Time for Hydrangea Pruning
It’s unavoidable. A few warm days, birds chirping, snow melting, and crocuses sprouting can only mean one thing. Time to get those pruners out and do a little trimming.
When it comes to hydrangeas, however, incorrect pruning is the biggest reason for lack of flowers. That’s because we prune them at the wrong time. So let’s get it straight once and for all.
Pruning New Wood
The ones you can prune now are those that flower on stems they will grow this year, i.e., new wood. Easier said than done since most of us don’t know which ones we have and what kind of wood they have. Let’s drill down a little deeper to figure that out.
Flower Shape and Foliage Clues
You can tell your hydrangeas apart by noticing the flowers and/or foliage. If the flowers are big, round, and either white or shades of pink, and it blooms early in the season, you have a woodland or smooth hydrangea. Botanically it’s known as hydrangea arborescens. Varieties like ‘Annabelle,’ ‘Incrediball®’ and ‘Invincibelle® Spirit’ are among the woodland hydrangeas in today’s market. Woodland hydrangeas never have blue flowers.
When your flowers are football- or cone-shaped, you have either a panicle or oak leaf hydrangea. Flowers start out cream, white or green, and age to shades of pink. No blue flowers ever on either of these two varieties.
If the foliage looks like an oak tree, you have an oak leaf hydrangea. How’s that for an easy identification? You might have ‘Alice’, ‘Snowflake’, or “Snow Queen’ among others. The oak leaf hydrangea flowers this year on the growth it put on last year, i.e., old wood.
Your panicle hydrangea (‘Limelight,’ ‘Vanilla Strawberry ™,’ ‘Strawberry Sundae®,’ etc.), on the other hand, flowers on the wood it will grow in the coming months, i.e., new wood.
Now you know that new wood flowering hydrangeas (woodland and panicle) are the only ones you should be cutting now. All the other flowers on old wood. If you cut the old wood bloomers too early, i.e., now, you risk losing your flowers.
How Much to Cut
You can take your woodland hydrangeas down to about 18-24 inches. But don’t go further than that, if even that much. You need strong stems to hold up the flowers, especially after a rainstorm. The older the stems are, the stronger they become so let them be. You can even leave up a few taller stems to form a supporting framework. They will disappear into the plant once it leafs out.
For your panicle hydrangeas, you can cut them down by at least one-third. You might want to take even more if the plant has become distorted from snow load and other causes.
Be comforted in knowing it’s very hard to make a mistake when it comes to pruning new wood hydrangeas. They are very forgiving in that they always grow back and fill in.
What about Old Wood Hydrangeas?
These are the ones I call the troublemakers. Old wood hydrangeas come in a few flavors. Some are the ones with the round flowers that you can sometimes change to shades of pink or blue. They can either be mountain hydrangeas (serrata), or big leaf hydrangeas (macrophylla). Climbing hydrangeas (petiolaris) and oak leaf hydrangeas (quercifolia) also flower on the growth they produced last year.
Develop a New Love for “Broccoli”
For all old wood hydrangeas, with the exception of dead, diseased or damaged wood, you must hold off cutting until you see their little buds called “broccoli.” It’s only when those buds emerge that you will know which stems to discard. However, if you need to cut your plant back because it has outgrown its allotted space, then have at it knowing the potential consequences. A point to remember is that some people never cut their old wood hydrangeas and the plants do just fine.
Keep in mind there’s no guarantee of flowers from old wood hydrangeas if your plant has lost its buds to weather or whatever. Many areas had a rapid and deep freeze last November before the hydrangeas had a chance to harden off. There is a prevalent fear that cold spell killed the buds that were already formed. If this is your story, you will get a nice green bush but no flowers.
The Magic of Reblooming Hydrangeas
Here’s the saving grace. With a big leaf or mountain hydrangea that reblooms (not possible on oakleaf and climbing), you can still expect to get flowers from that plant even if the terminal buds were destroyed. Rebloomers have the amazing genetics to produce flowers on new stems they will generate in the current season as well as along the stems of last year’s growth
But you must give them the proper cultural conditions to do that. The right amount of fertilizer (applied now), moisture, and light (part sun) will keep them happy. Then they can concentrate on mid-season flower production.
Before you trim your hydrangea, figure out which type of hydrangea you have and if it blooms on old wood or new wood.
So you see, this hydrangea pruning thing is really pretty simple. All you need is a sharp pair of pruners to get those new wood bloomers off to a good start.
“This post is provided as an educational/inspirational service of the National Garden Bureau and our members. Please credit and link to National Garden Bureau and author member when using all or parts of this article.”