When To Prune Hydrangeas

Why Didn't My Hydrangeas Bloom?

Blooming hydrangea bush
Tetsuya Tanooka/a.collectionRF/ amana images/ Getty Images

Hydrangeas make beautiful focal points in the garden and require minimal care, other than pruning. Many hydrangeas have interesting foliage and bark, but most are grown for their large showy blossoms. So it’s very disappointing when hydrangeas don’t bloom for a season. If that happens, it is probably one of three reasons.

  1. Either it did not get enough sun
  2. An early frost or cold spell killed the flowers buds or
  1. It was pruned at the wrong time

To complicate the issue, different types of hydrangeas need pruning at different times. You will have to know what type of hydrangea your plant is. Hopefully, you saved the label. If not, an educated guess can be made by looking at the foliage and flowers.

How to Prune Hydrangeas

When to prune a hydrangea generally depends on when it sets its flower buds. Other than the modern repeat blooming hydrangeas, like 'Endless Summer' and  'Lime Light', most older hydrangeas set the next season's flower buds in either late summer/fall or during the growing season.

In a Nut Shell:

  1. Prune during the summer, just after the flowers fade:
    • Bigleaf or Florist Hydrangea (Hydrangea macrophylla)
  2. Prune in late winter or early spring:
    • Hills-of-Snow or Sevenbark Hydrangea (H. arborescens ‘Grandiflora’),
    • Oakleaf Hydrangea (H. quercifolia)
    • Peegee Hydrangea (H. paniculata ‘Grandiflora’),
    • Tea of Heaven (H. serrata)
  1. Prune as needed to control growth -
    • Climbing Hydrangea (H. anomala petiolaris)

Here are more specifics for each hydrangea type:

Bigleaf, Mophead, or Florist Hydrangea (Hydrangea macrophylla)

The popular mophead hydrangea is sometimes easy to recognize because it is the one whose flower color changes with the soil pH: blue in acid soil, pink in alkaline.

There are a few varieties that simply stay white, making it much harder to categorize them from the flowers. The leaves are coarsely serrated and glossy, dark green. Hydrangea macrophylla also include the Lacecap hydrangeas, whose flowers look like a circle of unopened buds surrounded by open petals. In reality, the unopened buds are the fertile flowers with pollen and the outer flashy petals are sterile and are just there to attract bees. This is true of most hydrangeas, so don’t become frustrated waiting for all the buds to open.

Bigleaf hydrangeas set their flower buds at the ends of the upright or lateral branches, during late summer to early fall. Pruning Bigleaf hydrangea in the spring or even late fall, after the buds have been set, will remove the flower buds and any chance of getting flowers that season.

Bigleaf hydrangea should be pruned as soon as the flowers have faded. You should begin to see new growth coming in from the base of the plant, about this time. To keep the plant vigorous, selectively prune out the dead and weaker stems, both old and new. Don’t prune out all the old wood, since this is what will keep flowering as the new growth matures.

Bigleaf hydrangeas are the variety most susceptible to winter bud injury.

If you live in an area with severe winters or your plant is exposed to winter winds, you might need to offer it some winter protection, to protect the flower buds. Tying the branches together and wrapping them with burlap isn’t pretty, but it could mean winter survival. Remove the burlap when the buds begin to swell.

Hills-of-Snow or Sevenbark Hydrangea (H. arborescens ‘Grandiflora’)

This hydrangeas doesn't usually have any problems blooming, although their white flowers are not as showy as we’ve come to expect from hydrangeas. Hills-of-Snow is a rounded shrub with leaves that are somewhat rounded with a pointed end and they are paler on the lower surface than on the top. Hills-of-Snow does not usually have trouble blooming because its flowers are set only on new growth. This is a good thing because it is very susceptible to winter injury and is often killed back to the ground, in colder areas.

If winter injury is not that bad, you can prune slightly by removing some branches to the ground and cutting others back to shape the plant.

'Annabelle' is a very popular Hydrangea arborescens cultivar with conical flowerheads that are considerably larger than ‘Grandiflora’. Its leaves are fuzzy gray on the lower surface.

Oakleaf Hydrangea (H. quercifolia)

It's probably not surprising that oakleaf hydrangea is easily recognized by its oakleaf shaped foliage. Since its major attraction is its foliage, loss of bloom is less disappointing than in other varieties. Oakleaf hydrangea also blooms on new season growth and can be pruned in late winter or early spring, while dormant, to remove dead wood. If it has experienced winter dieback, prune back to below the point of injury.

Peegee Hydrangea (H. paniculata ‘Grandiflora’)

This is the most commonly grown hydrangea variety. Peegee’s have massive snowball shaped flower clusters in mid to late summer. The flowers start out white and slowly turn pink, drying and remaining on the plant long after the leaves have fallen. These are also the varieties you see trained into standards that look like small trees.

Peegee’s don’t require hard pruning to the ground. New flower buds will be set on new spring growth. Some gentle pruning in late winter or early spring will not only keep the plants from becoming overgrown, it will also encourage more new growth and hopefully more flower buds. You can deadhead the flowers, as soon as they become unattractive and clean up the overall shape of the plant.

Tea of Heaven (H. serrata)

Tea of Heaven is a small shrub with narrow, pointed leaves and flattened flowerheads. It is sometimes confused with H. macrophylla because the flowers can look like lacecaps and/or be blue or pink, but it by no means has big leaves. H. serrata also blooms on new wood and should be pruned in late winter or early spring.

Climbing Hydrangea (H. anomala petiolaris)

The stunning climbing hydrangea is the type you see slowly making its way up a tree or support.

It is actually a vine, not a shrub and requires little to no pruning. Once climbing hydrangeas become established, they can grow quite vigorously and may need occasional summer pruning to stay in bounds.