Big, beautiful blooms, sometimes as big as softballs, in soft shades of white, pink, and blue, make these old-fashioned shrubs a long-time favorite.
Knowing when and how to trim them can cause a gardener considerable worry. Old wood or new wood? In the spring or fall? To the ground or just a small trim?
Don’t worry. It’s not as confusing as you might think.
With the rise in popularity of these garden beauties, there are hundreds of new varieties. Breeders have been developing these shrubs to have gorgeous flower colors and grow in sizes more suited to smaller gardens. Breeders have also made them easier to care for – that includes pruning!
There are only a few simple rules to remember. In fact, some hydrangeas don’t need a lot of pruning, and some never need to be trimmed at all. Let’s demystify the process so you can master this garden chore with confidence.
1. Identify Your Type
Different species have different flowering patterns, which means different pruning times. Don’t know what kind you have? There’s a short identification guide at the end of this article.
2. Figure Out The Species
Latin, or scientific, names tell you the genus, the species, and the cultivar name. The species name is the second name after “Hydrangea.” The species name will guide you in regards to when to prune.
3. Don’t Trim Too Often
Hydrangeas do not need to be trimmed often. When you trim them, don’t trim too much. You should remove dead and broken branches, branches that cross and rub against each other, and dead flower heads. When choosing between branches that rub against each other, cut away the weaker limb.
4. Buy a Plant That Fits Your Space
Since hydrangeas shouldn’t be pruned very often, shop wisely and choose a variety that will fit in your garden. Don’t buy a shrub that will get 8 feet wide if you only have space for a 4 foot one.
5. Save The Plant Tag
The plant tag carries a wealth of information and often includes pruning recommendations. Save it in a drawer or take a picture of it before throwing it away so you can refer to it in the future.
6. Trim Hydrangeas That Bloom on Old Wood Right After They Are Done Flowering
For hydrangea species that bloom on old wood, or stems that grew the previous year, prune them right after they have finished flowering. The following season’s flower buds form in late summer or fall. If you trim after the buds set, you could cut them off, and you won’t have any flowers next summer.
An easy way to remember the species that bloom on old wood is to remember the acronym MASQ.
- Bigleaf or French varieties (H. macrophylla) should have a third of the oldest stems removed all the way to the ground in autumn. This keeps your plant vigorous and “young.” None of the branches will be older than three years old.
- Climbing varieties (H. anomala, formerly called H. petiolaris) grow so slowly that they seldom need pruning. Only remove dead or damaged stems or if you need to direct its growth.
- Mountain varieties (H. serrata) are treated just like the Bigleaf species.
- Oakleaf varieties (H. quercifolia) also don’t need pruning. Only remove any dead and broken branches.
7. Prune Hydrangeas That Bloom on New Wood in Late Winter
Prune hydrangeas that bloom on new wood in late winter or early spring. Pruning encourages new stems, and more stems mean more flowers!
- Smooth varieties (H. arborescens) can be cut all the way to the ground in early spring. In colder zones, these shrubs die back and are often treated like a hardy perennial. In warmer zones, cut them to the ground before they start leafing out because these old stems won’t produce any flowers.
- Panicle varieties (H. paniculata) should be pruned in late winter or early spring. Up to one third of the old stems can be removed to the ground. Older varieties of this shrub can get really large – up to 20 feet tall! Luckily, you can cut back the tops, creating a rounded shape, and not lose next year’s flowers. Tree forms should be pruned every year.
8. Hydrangeas That Bloom on Old and New Wood only Need Dead Flowers Removed
H. macrophylla and of H. serrata are cultivars that bloom on both old wood and new wood. The Endless Summer series and the Forever & Ever series have many beautiful varieties. The only pruning they ever need is removing their flower heads and dead or weak stems cut to the ground.
9. Prune By Using Loppers or Hand Pruners.
Don’t use manual hedge shears, and definitely don’t use power trimmers!
10. For all hydrangeas, remove dead flower heads in late winter or early spring.
Some gardeners don’t like the look of dried flower heads in winter. If that’s the case for you, trim them off at any time. Cut just under the flower head.
11. Made a mistake?
Not to worry, these plants are very forgiving. If you accidentally cut when or what you shouldn’t have, let it grow for a year. You’ll get those beautiful blooms next year!
Know Your Hydrangea: A Quick ID Guide
If you lost the plant tag or inherited hydrangeas when you moved into your home, you may have no idea what kind you have. Here’s a quick guide to some of the defining characteristics of the different species. With so many cultivars on the market, your specific plant might look a little different!
Bigleaf hydrangeas have large serrated leaves and large flowers that are either mophead or lacecap. The mophead varieties are also known as hortensias. These shrubs grow 3 to 6 feet tall, are hardy to zone 6 and marginally hardy to zone 5. They might not flower in cooler zones as cold weather can kill the buds. Common cultivars are Nikko Blue and Charm.
Climbing hydrangeas are woody vines with glossy green leaves and white flowers. They have tiny rootlets that attach themselves to trees and walls. They are slow to get established and it can be many years before they reach their mature size.
Mountain hydrangeas are related to bigleaf but have narrower leaves, smaller flowers, and grow to about 5 feet tall and wide. In the Tuff Stuff series and the Let’s Dance series are several plants with improved cold hardiness.
Oakleaf hydrangeas have a coarse texture, peeling bark, leaves shaped like oak leaves that color red in fall, and white flowers on long panicles. The flowers change from white to pinky-brown and then to brown. This shrub grows 4 to 6 feet tall and wide and can have a suckering habit, sometimes creating a thicket.
Arborescence, or smooth, hydrangeas, has smooth leaves, rounded white flower heads, and grows 3 to 5 feet tall and wide. The flowers can be gathered to make dried bouquets. Annabelle, Grandiflora, and the Invincibelle series are easy-to-find varieties.
Panicle hydrangeas, sometimes called PeeGee, have toothed leaves, white cone-shaped flowers that age to a purple-pink, and can be over 10 feet in height and spread. Older cultivars include Tardiva, Unique, and Grandiflora (PeeGee, for paniculata grandiflora). Limelight, Quick Fire, Pinky Winky, and Vanilla Strawberry are newer varieties.
If you want a more in-depth identification guide, make sure to check out our comprehensive guide on identifying different hydrangea species.