To prune or not to prune? This is one of the quintessential gardening questions. Recently, I asked a top landscaper in Virginia to weigh in on the issue. “When is the best time to prune hydrangeas without cutting off next year’s flowers?” I asked. Her reply?
“Never,” she said with a laugh. “But your best shot is after they’ve bloomed.”
It turns out that knowing how and when to prune hydrangeas involves first, identifying what kind of shrubs you own. And it all starts with determining whether they flower on old or new wood.
PRUNING HYDRANGEAS THAT BLOOM ON OLD WOOD
Nikko Blue hydrangeas bloom on old wood
Old wood is quite simply, last year’s wood. Hydrangeas that bloom on old wood set their flower buds on stalks that have been on the plant since last summer. This generally occurs sometime in August, September or October.
Hydrangeas that bloom on old wood include the mophead, bigleaf (macrophylla), lacecap and oakleaf varieties.
Oakleaf hydrangea is recognizable by its foliage that resembles oak leaves
When it comes to pruning, these beautiful shrubs require very little. But if you must, knowing when and what to cut is key. Most importantly, the more old wood you take, the fewer flowers you’ll have next summer.
Follow these three steps to maintain the health and vigor of your old wood hydrangeas:
- Immediately after flowering (and no later than July), prune flowering stems back to a pair of healthy buds.
- In late winter or early spring, prune out weak or damaged stems. Remove no more than 1/3 of the oldest stalks, taking them down to ground level.
- Repeat the process every summer to rejuvenate your shrubs and control their shape.
PRUNING HYDRANGEAS THAT BLOOM ON NEW WOOD
Limelight hydrangeas bloom on new wood
Hydrangeas that bloom on new wood set their flowering buds on the current season’s growth. Because their flowers come from new growth from the base of the plant, they can be pruned almost any time of year, except summer. Follow these three steps to maintain the health and vigor of these types of hydrangeas:
- Cut off faded blooms in late summer to improve the looks of the shrub.
- Prune out the oldest canes to improve vigor.
- Cut back the entire shrub in late winter before new growth starts to appear.
Additional tricks of the trade include leaving some of the older branches as a framework for new growth (these types of hydrangeas tend to open up and get floppy.) Many gardeners also advocate cutting the shrubs all the way back to the ground, which often produces bigger flowers.
Considered the crème de la crème of all the varieties that bloom on new wood, Hydrangea arborescens Annabelle is what is called a ‘smooth’ hydrangea. Smooth hydrangeas are known for their giant white blooms and are native to the southeastern United States.
Distinctive white blooms of Hydrangea ‘Annabelle’
What makes Annabelle so special is that it not only produces enormous, pure white flowers from June to August, but it also stays compact, growing to just 3 to 5 feet tall and wide. At first glance, it can be hard to tell this cultivar apart from other white-blooming hydrangeas. However, a number of gardeners go by this golden rule:
Annabelle flowers open lime green in early summer, change to bright white mid-summer and then switch back to light green in late summer before turning tan in the fall.
More recently, an improved version of Annabelle called Incrediball has been developed. It features basketball-sized blooms and thicker, sturdier stems that don’t flop over. In fact, they remain upright even in the rain.
‘Incrediball’ features 12″ flower clusters and blooms on new wood
Pruning hydrangeas like Annabelle can help control for shape and increase blooms. For this reason, some gardeners cut the shrubs back to the ground (within 6″) in late winter or early spring. Some say this encourages them to produce the largest flowers and sturdiest stems. But others claim it weakens the plants over time, causing them to need to be staked.
I recommend taking the middle road and pruning Annabelles back to between 1 and 3 feet above the soil.
PRUNING PANICLE HYDRANGEAS
Panicle hydrangeas bloom on new wood
Like Annabelles, panicle hydrangeas bloom on new wood. Since there’s no danger of cutting off blooms, they can be pruned in late winter or early spring before new growth. Cut them to the ground or to just a few feet above the soil depending on the size plant you want to maintain. The best known of the panicle hydrangeas include PeeGee and Limelight.
THE SUNNY SIDE OF LIMELIGHT HYDRANGEAS
When they were first introduced from Holland in the early 2000’s, Limelight hydrangeas took the garden world by storm. Featuring enormous, football shaped clusters of flowers, the shrubs performed great in full sun (although for best color, they require some shade).
Limelights keep their beautiful celadon color all summer long before aging slowly to pink. In the fall, they change to shades of dusty red and burgundy. Prune them like Annabelles.
Limelight hydrangeas bloom on new wood
ENDLESS SUMMER – THE BEST OF BOTH WORLDS
There’s a new kind of hydrangea in town called Endless Summer and it’s rocking the hydrangea world. Introduced in 2004 by Bailey Nurseries, Endless Summer hydrangeas bloom on both old and new wood. As a result, this gives them the ability to flower repeatedly all summer. The company’s tag line is, appropriately,
Experience life in full-bloom.
Endless Summer mophead variety
As of 2018, there are three different varieties currently available. Blushing Bride produces pure white mophead flowers that mature to soft pink. Twist-n-Shout is the first re-blooming lacecap variety. And BloomStruck has vivid purple or rose-pink mophead blooms that hold their color all summer. Summer Crush (available in 2019) will feature raspberry red or neon purple blooms.
It’s easy to imagine the benefits of plants that bloom on both old and new wood. Their flowers naturally last for most of the summer. Moreover, the company says Endless Summer hydrangeas bloom 10 to 12 weeks longer than average hydrangeas. Best of all, these hydrangeas need little to no pruning.
SOME COMMONLY ASKED QUESTIONS ABOUT HYDRANGEAS
Why are my hydrangea flowers turning brown in the summer?
The main reason that mophead flowers turn brown is too much sun; specifically hot mid-day to afternoon sun. To prevent this problem, site your shrubs in areas where they receive direct sun either in the early morning or late afternoon. Same goes for the lacecap varieties, which tend to have a much shorter flowering span than the mopheads. Attention to watering during dry spells also helps prolong blooms.
What do I do if my hydrangeas have grown too big and floppy?
Most gardeners advise waiting until the shrubs have been in the ground for 5 years before beginning a pruning program. If you’ve got the type that blooms on new wood, prune your shrubs in late winter or early spring for shape, taking them down to between 1 and 3 feet from the ground. If you’ve got the kind that blooms on old wood, follow the method above, removing 1/3 of the oldest living stalks each summer after the shrubs have flowered.
When I cut blossoms will it hurt the other blooms?
After August, cut only short stems to avoid affecting next year’s blooms
For hydrangeas that bloom on old wood, deadheading (or cutting flowers for indoor arrangements) can be performed on long or short stems in June through July without affecting next year’s flower buds. After August, it’s best to harvest only short stems.
Can I prune some of the branches and not affect others?
Yes. You are only cutting off the flower buds on the stalks that you prune.
Does watering keep the blooms going? Why do my hydrangeas look so dry in July?
As with all plants, watering during dry spells is key. Keep the soil moist around your hydrangea shrubs to keep the flowers going all summer.
I did all the right things and my hydrangeas didn’t bloom this year. What happened?
Weather can negatively affect blooms, too
Finally, you can follow all the rules and prune your new or old wood shrubs correctly, but weather can also have its negative effects, particularly frost. In colder regions, flowering can be adversely affected by either early fall or late spring frosts, making it confusing as to whether you pruned off the blooms yourself or left it to Mother Nature.