About half the pruning questions googled are related to hydrangeas.
Do it yourselfers all fear the same thing: Incorrect pruning will lead to a hydrangea that doesn’t bloom. And if your hydrangea doesn’t bloom, then what’s the point of having them.
The confusion is caused because some hydrangeas bloom on new wood, meaning the current seasons growth, while others bloom on old wood, which is last seasons growth.
Adding to the frustration is the fact that in colder climates old wood hydrangeas can fail you, even when you follow the old wood pruning rules. In this article we’ll cover when the different types of hydrangeas should be pruned, and what pruning techniques are best.
Pruning Hydrangeas That Bloom On New Wood
When a hydrangea blooms on ‘new wood’, it means that flowers bloom on flower buds that were formed that season. These flower buds weren’t there during the winter months. Instead they were formed when the hydrangea started putting out new growth in the spring.
New wood hydrangeas are either Annabelle’s (Smooth Hydrangeas), or Panicles, and they require different pruning techniques:
Annabelle Hydrangeas, also known as Smooth Hyrangeas, have stunning white flowers. There are two types of pruning you want to do with Annabelle Hydrangeas:
1. Rejuvenation– This type of pruning should be done in late summer/early fall as blooms begin to fade. Cutting off the faded blooms as well as the top one inch of growth will encourage the plant to produce additional blooms. This type of pruning can be done with hedge trimmers or bypass pruners. This type of pruning is kind of like giving your plant a light haircut.
2. Cut Back– In the early spring, before new growth starts to emerge, you can do a cut back pruning for your Annabelle Hydrangeas. This time your Annabelles should be pruned fairly close to the ground, almost as if you were pruning back a perennial. In fact you can prune them all the way to the ground but it’s best to leave several inches of last years wood to create a support structure for new growth. This will prevent the floppiness you sometimes see from Annabelle Hydrangeas. Your Annabelles will send up fresh growth from the base of the plant and blooms will appear on that fresh growth.
For help identifying Anabelle Hydrangeas, check out this link: Annabelle Hydrangea Identification
Panicle Hydrangeas (also known as Pee Gee’s) are tougher, more adaptable, cold hardy, and more reliable bloomers than hydrangeas that bloom on old wood. One of the simplest ways to identify a Panicle Hydrangea is by it’s cone shaped flowers. There are many types of Panicle Hydrangeas but some common varieties include: Limelight, Little Quick Fire, Vanilla Strawberry, and Pinky Winky.
Pruning Panicle Hydrangeas: Pruning Panicle hydrangeas should be done in early spring when the threat of frost is behind you. At this point you should see some green buds on the branches. Using trimmers, or pruners, cut off the top 1/3, or up to 1/2 of the plant. Although this type of pruning isn’t necessary it will help shape the plant and maintain it’s size since Panicles can get a little out of control if left untouched. This type of pruning will also help encourage new growth and will overall wake your Panicle up!
Annabelles and Panicles are great choices for colder climates (zone 5 or less). While every micro climate is different, a lot of people in these colder climates struggle with getting other types of hydrangeas (hydrangeas that bloom on old wood) to bloom, since frost can kill flower buds.
For help identifying Panicle Hydrangeas, check out this link: Panicle Hydrangea Identification
Pruning Hydrangeas That Bloom On Old Wood
When a Hydrangea blooms on ‘old wood’, it forms its flower buds shortly after blooms fade in late summer/early fall. This means that the flower buds and stems of the plant have to survive the winter for you to get blooms next spring/summer. If you’re in a warmer climate, this usually isn’t a problem.
If you’re in a colder climate, this is much harder. Cold winters can cause your hydrangea to die back.
In early spring you could be left with a bunch of dead branches that need to be trimmed way back (pic below). This means you won’t be seeing any blooms this year. This is a common frustration among people from colder regions. That’s why hydrangeas that bloom on old wood aren’t always the best choice for Zone 5 and colder.
Pruning Old Wood Hydrangeas: When pruning hydrangeas that bloom on old wood you have to be very careful with your timing. You want to prune when your hydrangea is just about done blooming for the year. Don’t wait too long. Shortly after blooms fade your hydrangea will start to develop next years flower buds. Pruning too late in the season would mean pruning off next years flowers! Don’t wait for the last bloom to fade, instead look for the plant to be winding down flower production. You’ll notice that the majority of blooms are weak and discolored. That’s the signal to prune.
Also, pruning in the spring and early summer would mean cutting off the flower buds that were set last fall. That’s why your only real safe time to prune is during the quick post flower bloom period.
Once flower blooms have faded, you can cut the top 1/3 of the plant using trimmers or pruners. This will help maintain shape and size.
Selective pruning is another type of pruning that applies to both new wood and old wood hydrangeas.
This means using a pair of bypass pruners and selectively cutting out branches that are dead, diseased, old and unproductive. You also want to cut out branches that are crossing, or touching each other.
Selective pruning can be done in early spring for all types of hydrangeas. Since you aren’t cutting the tops off of every single branch, you don’t have to worry about cutting off all your flower blooms if you have hydrangeas that bloom on old wood. Although, if you’re still nervous you may be cutting off flower buds, you can always selectively prune your old wood hydrangeas after the normal post flowering bloom period in late summer/early fall.
Remember, you’re only making some selective cuts to thin the plant out and get rid of the parts of the plant that are just depriving it of energy. This type of pruning helps prevent your hydrangeas from getting too bushy and overgrown. Bushy, overgrown hydrangeas could struggle to bloom as they mature. Take a look at the video below for some Selective Pruning tips. Notice what the plant looks like after pruning. The hydrangea is left with branches that are upright with plenty of space. There aren’t branches that are crossing, touching, or facing inward:
Deadheading Hydrangeas is when you simply prune off spent flowers, or flowers that are on their way out. By pruning off flowers that are dying back you help the plant focus its energy on producing more blooms, and overall this type of pruning is good for plant health. Use a pair of bypass pruners when dead heading hydrangeas.
This type of pruning can be done to any hydrangea at anytime during the growing season. Once again though, don’t get too crazy with the pruners on your hydrangeas that bloom on old wood if it’s getting late in the season.
What Happens If You Don’t Prune Hydrangeas?
If your hydrangea has plenty of space to grow freely, it may be completely healthy and continue to spit out blooms year after year without you pruning it at all. Other times, neglected hydrangeas can become overgrown and even worse they may stop blooming. A big reason why a lot of more mature hydrangeas fail to bloom is because the plant is spending a lot of its energy on leaf production and supporting older, unproductive parts of the plant. Thinning out older branches and weaker branches, as well as maintaining a healthy size and shape will help keep your hydrangea focused on flower production.
Why Are My Hydrangeas Not Blooming?
There are 7 main reasons why your hydrangeas aren’t blooming:
- Having hydrangeas that bloom on old wood in a colder climate where they die back during harsh winters, or flower buds get damaged from frost.
- Pruning hydrangeas that bloom on old wood after the flower buds have developed.
- Plant is not mature enough.
- Fertilizing with a high nitrogen fertilizer will encourage the plant to focus on green leaf growth instead of flower production. Instead use a fertilizer that’s meant for hydrangeas such as Holly-Tone 4-3-4.
- Not enough sun for Panicle hydrangeas. Panicle hydrangeas bloom best with 4-5 hours of sun. However If in southern zones avoid afternoon full sun exposure.
- The plant is overgrown and has too many branches. This will make the plant focus on leaf and shoot growth and less on flower production.
- Deer have eaten flower buds.
Hydrangeas That Bloom on New and Old wood
Want to make things really easy? There are a few hydrangeas that bloom on both new wood and old wood. These include Endless Summer Hydrangea, as well as Proven Winners ‘Lets Dance’, and ‘Tuff Stuff’. Planting these varieties makes it a lot easier to avoid pruning mistakes.
Hydrangea Identification Help
If your hydrangeas are in bloom then identification is much easier. Check out this quick video, and you will be able to see what kind of hydrangea you have: Hydrangea Identification
If it’s late winter or early spring and your hydrangeas aren’t in bloom then identification is much harder.
Say you just moved into a new home, or maybe you haven’t paid much attention to your hydrangeas before. You may have no idea if you have and old wood hydrangea or a new wood. There’s no need to worry. The best thing you can do is wait!
Wait until late spring or early summer (or earlier depending on location) when hydrangeas are starting to put on new growth, and leaves have developed. By then you should be able to use the leaves for identification. This is a great site for identifying hydrangeas by leaves (leaf identification is towards bottom of the post): Hydrangea Leaf Identification.
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