Plant Hydrangeas

When and How Should you Prune Hydrangeas?

A lot of people get confused about the pruning of hydrangeas. Should you prune them? If yes, then when and how should you Prune Hydrangeas?

The decision of when to prune Hydrangea depends on whether yours is an Old wood Bloomer or a new wood bloomer.

When to prune Old wood bloomers Hydrangeas?

Old wood means that the plant stemmed from the previous summer. Hydrangeas that flower on old wood set their flower buds on stems that have been there since the previous year.

You should prune Old wood bloomers Hydrangeas just after they have blossomed, usually late summer.

Hydrangeas that bloom on old wood include mophead, bigleaf (Macrophylla), Lacecap, and Oakleaf varieties.

When to prune New wood bloomers Hydrangeas?

New wood refers to the stems that form during the current flowering season. The hydrangea varieties that grow flowers on new wood start to develop buds on these stems that have grown during the current season.

The flowers come from new growth from the base of the plant, therefore, these Hydrangeas can be pruned at almost any time of the year except the summer.

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When to prune popular hydrangea varieties?

Let us look at some of the popular varieties of Hydrangeas and determine when is the best time to prune them.

Bigleaf hydrangeas

Bigleaf hydrangeas (Hydrangea Macrophylla) have very long, large dark green leaves up to 8 inches. They bloom through mid-summer to late summer. Bigleaf hydrangeas have large, rounded flowers.

The color of the flowers depends on the pH of the soil. Acidic soil causes flowers to be blue, while alkaline soil results in pink flowers.

Bigleaf hydrangeas grow on old wood. You will have to prune this plant just after it has finished flowering.

Smooth hydrangeas

Smooth (wild) hydrangeas (H. arborescens) bloom in spring or early summer. The flowers are big and round. They come in either white color or shades of pink. The most common garden variety of smooth hydrangeas is Annabelle. It is identified by its large flowers shaped like round snowballs.

Smooth hydrangeas flower on new wood. That is why you need to prune it in late winter or early spring.

Panicle hydrangeas

Panicle (peegee) hydrangeas (H. paniculata) have large, cone-shaped flower panicles. As the flowers start to bloom, they are white or greenish in color, but they gradually start turning pink.

Panicle hydrangeas also grow on new wood, which means that you need to prune it in late winter or early spring.

Oakleaf hydrangeas

Just like the name suggests, oakleaf hydrangeas (H. quercifolia) have leaves like those of oak trees. The flowers of oakleaf hydrangea bloom early in the season. At first, they are cream or greenish in color and eventually turn pink.

Oakleaf hydrangeas grow on old wood. That is why you need to prune right after it has flowered.

Mountain hydrangeas

Mountain hydrangeas (H. serrata) resemble bigleaf hydrangeas, only in a compact form. The flowers of this plant are shaped like lacecaps, and the color depends on the pH of the soil.

Mountain hydrangeas bloom on old wood. However, this plant is small in size – 2 to 4 feet. This means that it does not require pruning very often. If you still want to prune, do so immediately after flowering.

Climbing hydrangeas

Climbing hydrangeas (H. anomala subsp. petiolaris) are rapid climbing vines. They grow up to as long as 40 feet. This plant has white flowers that bloom in spring or early summer. The flowers bloom in flattened clusters that are up to 8 inches wide.

Climbing hydrangeas grow on old wood. So when pruning is needed, it will be done after the flowers have faded.

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How to prune hydrangeas?

Here is how you can prune popular varieties of Hydrangeas

How to Prune Bigleaf hydrangeas?

Bigleaf hydrangeas grow on old wood, which means that they set their flower buds from late summer to early fall.

If you try to prune your hydrangea in spring or even in late fall, all the flower buds will be removed, and there won’t be any blooms for a year.

Bigleaf hydrangeas don’t actually require any pruning. However, if you need to prune the plant to control its size or shape, make sure you prune it just after the flowers have faded.

Also, remember never to prune more than one-third of the total growth.

Deadhead faded flowers

You can trim the spent flowers so that your plant looks clean. Clip the faded flowers with the help of bypass pruners.

Prune dead stems

You can start to prune your hydrangea when you notice that most of the flowers have faded. Prune stems that are dead or look weak.

However, be careful not to cut away all the old wood, as bigleaf hydrangea blooms on old wood. This is where the flowers will bloom as the new growth matures.

Prune for size

If your plant has grown beyond its space, you can prune it to keep the size in check. You can prune some selected branches all the way down to the ground or up to the main stem, but do not prune away all the healthy branches so that you do not lose all the flowers.

You can prune about one-third of a bigleaf hydrangea, but pruning it harshly can weaken the plant for a season or two.

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How to prune Smooth hydrangeas?

Smooth hydrangeas include cultivars like Annabelle, Grandiflora, and Incrediball. This hydrangea has quite ordinary white flowers and blooms fairly easily.

This is a round shrub with leaves that are rounded and pointy at the tip. The color of the leaves is paler on the underside.

Smooth hydrangea blooms on new wood and does well with aggressive pruning.

Remove dead branches:

Smooth hydrangeas grow on new wood. So, pruning in early spring will ensure that there is a lot of new growth for blooms. Remove any branches that are dead or have been injured during the winter. Prune the branches up to the main stem or even to the ground level.

Trim for shape:

This shrub has a rounded shape. So you can trim some additional branches as well in order to control the shape of the plant. You can lightly prune the plant so that it produces a large shrub with a lot of smaller flower heads. “Light pruning” means that you can trim up to one-third of each stem’s length.

Prune hard for large flowers:

Aggressive pruning of a smooth hydrangea 12 to 18 inches from the ground will result in a shrub that produces fewer but larger flower heads. These flowers are much larger than normal, so much so that sometimes they might require propping.

How to Prune Panicle hydrangeas?

Panicle hydrangeas, also known as pee gee hydrangeas, produce flower clusters that are shaped like cones or a football. These flowers bloom during mid to late summer.

They start off white, cream, or green in color, gradually turning pink. Even after these blooms dry, they stay on the plant, even after all the leaves have fallen.

Panicle hydrangeas grow on new wood. They prefer heavy pruning.

Deadhead faded flowers:

You can remove the spent flowers as they fade during the growing season. This will also help prolong the blooming of the flowers, as the plant will put more energy into new growth as you prune the old blooms.

Prune lightly to keep shape:

As the flowers start to fade and become unattractive, you can trim the plant lightly to maintain the shape. Prune selected branches that disrupt the look of the plant. Panicle hydrangea is an attractive plant to look at, even after blooming is over.

Prune hard in late winter or early spring:

Flower buds on panicle hydrangeas develop on the new growth that happens during spring. Hard pruning some individual stems in late winter or early spring will prevent the plant from overgrowing its space. At the same time, it will also encourage the healthy growth of plants and flowers.

You can prune one-third of the total mass of panicle hydrangeas without causing any damage to the plant.

The best way to prune is to trim the smaller wood down to the ground level while leaving the larger stems intact. If you need to maintain the size of the plant, you can also partly trim the larger stems.

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How to prune Oakleaf hydrangeas?

Oakleaf hydrangea is known for its foliage that is shaped like oak leaves.

The main attraction of this plant is not its blooms, but the foliage. This shrub flowers on old wood, so if you want to prune, you should do so immediately after the plant has stopped flowering.

Pruning in oakleaf hydrangea is done to maintain the shape or size of the plant and not to stimulate new blooms, so be careful while trimming this plant.

Prune winter dieback:

Check your plant in early spring, before new growth begins. If you notice that your shrub has experienced winter dieback, prune the stems to below the point of injury. You should wait until the plant has finished flowering for any more pruning.

Prune for shape:

Oakleaf hydrangea grows on old wood, so heavy pruning should be done right after the plant has finished flowering. You can use sharp bypass pruners to remove stems and branches in order to get the desired shape for your plant.

Oakleaf hydrangea does not like heavy pruning, so do not trim more than one-third of the total mass of the plant. It is not even necessary to prune this variety, so you do not need to do it unless you want to maintain the shape or size of the shrub.

Cut the stems just above the point where they meet the main stem.

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How to prune Mountain hydrangeas?

Mountain hydrangeas are small in size, with narrow, pointed leaves and flattened flower heads. This plant is very similar to Hydrangea macrophylla, especially the flowers.

However, this plant is much smaller in size and does not have the big leaves of Hydrangea macrophylla. This plant does not need to be pruned at all, but if you want to trim it to maintain the size or shape, do it carefully. This plant blooms on old wood.

Remove damaged stems in early spring: If there are any stems that are dead or have been damaged due to winter injuries, you can remove them right up to the ground level in early spring, before new growth begins.

Prune for shape: This shrub does not need to be pruned annually. If you have to prune, do so after the plant has finished flowering. Use bypass pruners to trim back the stems.

How to prune Climbing hydrangeas?

The climbing hydrangea is not a shrub, but a woody vine. It grows upwards by using another tree or any external support. It does not require any pruning except to control the size.

Climbing hydrangea blooms on old wood grown in the previous season, so if you have to prune, you need to do it immediately after the plant has flowered.

Prune to maintain size: As climbing hydrangeas are established, they can grow rapidly and might need to be pruned to control their size. Prune the vines right after the plant flowers. Most of the flowers develop at the top of the plant, so trimming the sides will not have a lot of impact on the appearance of the plant.

Prune to refresh the plant: Any overgrown or neglected vines can be trimmed back to the ground level in early spring in order to rejuvenate the plant. However, this can reduce the flowering for a season or two.