How and When to Prune Panicle Hydrangeas – Plus, the Common Mistake Most Gardeners Make
A plant expert reveals how to prune panicle hydrangeas the right way for the biggest blooms and healthiest plants. Plus, one common mistake that ruins blooms!
Hydrangeas are the rock stars of the flowering shrub world and panicle hydrangeas are among the most popular varieties. You may know them as pee-gee hydrangeas, but there are dozens of panicle hydrangeas and more new cultivars almost every year.
These beautiful shrubs are beloved because they are some of the easiest hydrangeas to grow and are perfect for beginners. And with so many cultivars available, there is a panicle hydrangea that's perfect for every garden.
But the question becomes, with so many different types, how and when do you prune them for the best results? Improper pruning can reduce the number of flowers, so you’ll want to learn how and when to prune hydrangeas before picking up your clippers. The following expert advice cover everything you need to know to safely prune your panicles.
Panicle Hydrangea Basics
Panicle hydrangea (Hydrangea paniculata) are sometimes called the “black thumb” hydrangeas because anyone – even a beginner – will have an easy time growing these shrubs.
Other types of hydrangeas require dappled sun or even light shade, but not panicles. They are by far the best hydrangeas for full sun gardens. Plus, panicles are some of the hardiest of hydrangeas around and thrive in a wide range of winter climates, including USDA growing zones 3-9.
They are so ornamental, too! The huge flowers grow in white, but as summer wanes and fall approaches, they take on pink to red tones. Blossom color varies in some cultivars. For example, ‘Limelight’ hydrangea blossoms grow in green before turning red or burgundy.
Though pruning panicle hydrangeas is not mandatory, many gardeners decide to cut back shrubs to encourage thicker stems, bigger blooms from buds on the lower parts of the stems, and a more attractive shape.
When to Prune Panicle Hydrangeas
Hydrangea pruning can feel complicated since some species bloom on new wood and others bloom on old wood. The timing of pruning is critical for species that bloom on old wood and even a simple hydrangea care mistake can eliminate the next season’s blooms.
Panicle hydrangeas bloom on new wood. That means that you don’t have to be quite as stressed about the timing of the pruning. The two best times to prune panicle hydrangeas are late fall, once the plant is dormant, and late winter or early spring, when new growth begins. I prefer early spring because then I get to spend the winter looking at the dried flower heads rather than cut-off branches.
When not to prune panicle hydrangea? Summer, hands down. The very worst time to prune panicle hydrangeas is in early summer before flowers emerge. Panicles bloom in late summer and – if you prune before then – you’ll cut off all the flower buds. This is a common mistake when pruning panicle hydrangeas as well as many other shrubs in the landscape. But thankfully, it's easy to avoid.
How to Prune Panicle Hydrangeas
A panicle hydrangea looks best when it is regularly refreshed. You’ll want to take off about one-third of the shrub every year. For example, if your panicle is 6 feet (2 m) tall, prune off about 2 feet (.6 m) at the top.
Alternatively, you can try a simple rejuvenation pruning technique. Take out about one-third of the branches, selecting the oldest branches first. Continue this over the course of three years, taking out a different one-third each year until the entire shrub has been refreshed.
In addition, take a close look at the shrub. Are there any thin, spindly stems? Trim out these to create a more pleasing shape. Also, trim out any thin side branches, remove any crossing branches, and prune away any dead or diseased stems. Always use a pair of sharp, clean pruners, like these ones from Fiskars that our team of experts love. Or splurge on the Felco pruners pro gardeners swear by.
Pruning Panicle Hydrangeas Into Trees
Do you want a hydrangea into the form of a small tree? Pick a panicle. It’s the only hydrangea species that can be pruned into a tree.
The pruning process to create a tree hydrangea starts early by identifying and encouraging a central trunk. If you are buying a panicle tree from the nursery, they will have done the initial shaping work for you.
But you’ll still need to prune your tree hydrangea regularly to hold that shape. This is mandatory. if you skip even one year, tree top growth can become out of control and ruin the shape. If this happens, it is very difficult to restore the tree form.
