Determining when to prune hydrangeas comes down to whether or not your Hydrangea blooms on New Wood or Old Wood.
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 Hydrangeas, have stunning white flowers. There are two types of pruning you want to do with Annabelle Hydrangeas:
1. Rejuvenation Pruning– 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 the plant 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 the shrub a light haircut.
2. Cut Back Pruning– 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 tough, adaptable, cold hardy, and more reliable bloomers that bloom on new 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.
1. Shape and Size Pruning- 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!
2. Selective Pruning– This type of pruning can be done in early spring when the threat of frost is gone. With selective pruning you use a pair of bypass pruners and selectively cut out branches that are dead, weak, diseased, crossing, touching, old and unproductive. Here’s a quick video of a panicle hydrangea that was selectively pruned in early spring:
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.
1. Shape and Size Pruning– 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 in late summer/early fall. 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.
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.
2. Selective Pruning– This type of pruning can be done in early spring when the threat of frost is gone. With selective pruning you use a pair of bypass pruners and selectively cut out branches that are dead, weak, diseased, crossing, touching, old and unproductive.
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.
Do You Need to 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.
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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