Pruning hydrangeas: when & how

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David
David
David

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When should hydrangeas be pruned, and what is the correct pruning method for different hydrangea varieties? Below are detailed instructions on how to properly prune hydrangeas.

deadheading a hydrangea
Proper pruning is necessary for truly healthy – and beautiful – hydrangea plants [Foto: S.O.E/ Shutterstock.com]

Regularly pruning hydrangeas is essential for their health and flower production. When and how often to prune often depends, however, on the hydrangea variety: panicle hydrangeas (Hydrangea paniculata) and smooth hydrangeas (Hydrangea arborescens) flower every year, and can be regularly pruned. Other varieties such as the beloved Hydrangea macrophylla (commonly referred to as bigleaf or French hydrangea) sometimes skip a year between flowering, and an aptly timed prune can help prevent a gap year in flowering.

The first step in pruning is to determine your hydrangea plant’s variety. French and Oakleaf hydrangeas (Hydrangea quercifolia) first form their spring flowers in the autumn, in other words, these types of hydrangeas bloom on last year’s wood. Cutting hydrangeas back too much can risk unintentionally pruning beautiful flowers. Panicle hydrangeas (Hydrangea paniculata) and smooth hydrangeas (Hydrangea arborescens) bloom on new wood meaning that they form their flowers the same year they bloom. Both panicle and smooth hydrangeas can be cut back without any risk of accidentally cutting off blooms.

When to prune hydrangeas

While hydrangeas can be cut either in autumn or spring before new shoots form, there are certain advantages and disadvantages to pruning in each season:

Pruning hydrangeas in autumn

Those who prune their hydrangeas in autumn should consider the following:

  • Dried-up flowers no longer carry the risk as a potential breeding ground for fungal pathogens.
  • If the hydrangea is not sufficiently protected, frost will easily penetrate the vulnerable trimmed spots and damage the plant.
pruning a hydrangea in fall
Frost can penetrate hydrangeas after a fall pruning [Foto: S.O.E/ Shutterstock.com]

Pruning hydrangeas in spring

Springtime pruning carries the following pros and cons:

  • Dried flowers are decorative.
  • Little risk of frost damage.
  • If you need to cover the hydrangea to prevent frost damage, mould will develop quickly due to the dried plant’s poorer air circulation.

Instructions: how to prune hydrangeas

Pruning should be adjusted to the variety of hydrangea that has been planted. We will focus on the classic hydrangea macrophylla, which blooms on old wood, and the smooth and panicle hydrangea, which bloom on new shoots.

Pruning Hydrangea macrophylla correctly

With Hydrangea macrophylla, heavy pruning should be avoided when possible. Most varieties will not flower after being excessively pruned, it is better to correct the shape by annually pruning shoots. With some newer hydrangea macrophylla varieties, however, this is no longer necessary as they are remontant which means that they flower on young shoots several times a year.

When to deadhead hydrangeas in autumn: Ideally, dried flowers should be pruned in autumn, but spring pruning is also possible. It is important to cut just beneath the flower stalk, so as not to endanger next year’s flowers.

  • Deadhead hydrangeas: Remove sick and weak shoots. This reduces the risk of mould and allows light to better reach the plant.
  • Remove any old shoots: Older shoots, especially with a lot of branches at the base, should be removed in time. Depending on the size and age of the hydrangea, shoots can be cut off a few centimetres above the ground. Removing old shoots will help the plant develop new shoots and put more energy into flowers on the young and vital branches.
  • Avoid excessive pruning.
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Pruning smooth and panicle hydrangeas correctly

Hydrangeas that flower on annual wood, i.e. fresh shoots, are usually much less complicated in terms of care. A single cut can be used to remove withered blooms and to correct the plant’s overall shape. Smooth and panicle hydrangeas can be pruned to a height of 30 centimetres, which will promote branching. When pruning smooth and panicle hydrangeas, make sure to prune before new shoots form in autumn or if you live in a colder region, in spring.

Pruning climbing hydrangeas correctly

Climbing hydrangeas (Hydrangea petiolaris) do not need any sort of pruning, though flowers from the previous year should be removed. This not only makes the plant look neater but will also protect the plant against fungal outbreaks. Should the climbing hydrangea begin to grow too tall, do not hesitate to cut it back. You can find more about how to properly cut climbing hydrangeas in this article. Like the French hydrangea, climbing hydrangeas may skip a year between flowering, as the plant only blooms on perennial wood.

If you would like to learn more about the different hydrangea species and varieties, you can find further information in this article.

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