When To Prune Hydrangeas In The UK

Hydrangea

Almost all hydrangeas should be pruned in late winter or early spring, with the exception being the climbing hydrangea which is pruned after flowering in summer. Before you start hacking back your shrub you first need to identify which type of hydrangea you have in your garden. This is because different types of hydrangeas need different methods of pruning.

The most common hydrangeas planted in UK gardens are mop-head and lace-cap hydrangeas. These types of hydrangeas produce flowers on older wood, so you don’t prune them hard. Leave the old flowers on over winter as this provides protection to developing buds during a cold snap.

Then in spring simply dead-head them, cut back an inch or two down to the nearest set of healthy buds. If you have a really overgrown shrub, take out two or three of the main stems at the base, and your hydrangea will send up new shoots. This new growth will not flower in the coming summer but it will help to reshape your shrub.

So if you cut back your mop-head or lace-cap right back to the ground, your hydrangea won’t flower that year. Which is one of the most common questions asked about Hydrangeas, “Why isn’t my hydrangea flowering?”, and this is the reason why because all the older wood has been pruned to hard and the new growth that shoots up doesn’t flower that year.

If you wish to renovate your hydrangea and still have it produce flowers in the summer then this can be done over a three year period by cutting back a third of the shrub each year and this will totally rejuvenate your plant.

A different type of hydrangea, hydrangea paniculata produces flowers on new growth and needs no pruning if you wish to let it grow to its ultimate height, which is about 10 feet. If you wish to contain your paniculata you need to prune in spring creating a framework from which new growth can shoot from. It doesn’t matter how hard it is pruned, just cut back to your desired shape and size, and it will still flower on the new growth produced during the up and coming summer.

If you are unable to identify which type of hydrangea you have planted in your garden, simply dead-head in the spring and watch carefully during the summer to see if flowers are produced on new or old wood. If it produces flowers on new growth you can prune it back hard next spring if you wish.

Below is a list of the different types of hydrangeas to help you with which variety you have planted in your garden.


Types of Hydrangeas

Mop-Head Hydrangea

Mop-Head Hydrangea

The most common hydrangea planted in UK gardens, that produces big dome-shaped clusters of flowers in blue, pink or white. The scientific name hydrangea macrophylla translates into big or large leaved, which is one of the common name’s for a mop-head, big leaf hydrangea. An other common name is florist hydrangea, because of the popularity of their use in the floral industry.


Lace-Cap Hydrangea

Lace-Cap Hydrangea

Lace-cap Hydrangeas are very similar to a mop-head, but instead of producing a round dome of showy flowers a lace-cap produces delicate flower clusters of small fertile florets with scattered showy sterile florets to form a ring. A lace-cap hydrangea is generally hardier than a mop-head too.


Climbing Hydrangea

Climbing Hydrangea

Latin name hydrangea petiolaris, climbing hydrangeas are a useful low-maintenance climber for a shady or north positioned wall. Native to the woodlands of Japan, Korea and Siberia in Russia, where it grows up tress and across rock faces. The flowers a climbing produces are not too dissimilar to a lace-cap hydrangea, with flowers in clusters comprising of both small fertile and more showy sterile flowers.


Mountain Hydrangea

Hydrangea serrata species was formerly grouped with the lace-cap hydrangea because of its flattened flower-heads that consist of central, small florets surrounded by showy, larger florets. Mountain hydrangeas are typically smaller and more compact than the common mop-head hydrangea.


Smooth Hydrangea

Smooth Hydrangea

Native to the United States and commonly known as wild hydrangea or sevenbark. The reason behind it being called “sevenbark” is because the stem bark has a tendency to peel off in several successive thin layers with different colours. Smooth hydrangeas produce exceptional giant white booms on new wood.


Rough-Leaved Hydrangea

Rough-Leaved Hydrangea

Hydrangea aspera are native to the Himalayas, Central and Western China, and were first introduced to the UK in 1908 by Ernest Wilson. The rough-leaved hydrangea produces flowers similar to a lace-cap hydrangea.


Oak-Leaved Hydrangea

Oak-Leaved Hydrangea

Hydrangea quercifolia is commonly known by its translation oak-leaf hydrangea and is native to South-eastern parts of the United States. It produces long pointed white flowers with leaves shaped like giant oak leaves that go a striking orange-red colour in autumn.


Hydrangea Paniculata

Hydrangea Paniculata

The panicled hydrangea is native to China, Korea, Japan and Russia. The name “paniculata” comes from the fact that many of the blooms are panicle-shaped (somewhat coneshaped) rather than ball-shaped.


How To Prune Hydrangeas

As mentioned at the start of this article mop-head and lace-cap require minimal pruning as they produce flowers on old wood. Simply deadhead in late winter or early spring by cutting last year’s spent flowers off and prune an inch or two down to the next set of healthy buds that should be developing.

Mountain, oak-leaf and rough-leaf hydrangeas also only need the same minimal pruning as the mop-head and lace-cap require.

Poor or neglected hydrangeas can be entirely renovated by cutting off all the stems at the base. However, this will remove all the flowers for that summer, and the new stems will not bloom until the following year.

The paniculata and smooth hydrangea are also pruned in late winter or early spring, but they can be hard pruned if needed as they produce flowers on new growth. To maintain a permanent framework cut back last year’s stems to a pair of healthy buds.

To produce larger flowers hard prune to the lowest pair of buds, this will create a low framework of branches of no more than 12in (30cm) high, but if more height is required prune to about 24in (60cm) tall.

When pruning your hydrangea remember to remove any crossing, dead, damaged, straggly and weak stems. Also cut out any stems that trail onto the ground.

If there has been any frost damage in the spring, cut back damaged shoots to just above the first undamaged pair of buds on live and healthy wood.

Climbing hydrangeas should have over-grown and unwanted shoots cut back directly after flowering has finished. Most flowers are produced towards the top of the plant, so try to leave as much of this un-touched as possible.

Established climbers will tolerate a hard prune in spring, but extensive renovation in one go is more than likely to reduce flowering for the next couple of years. To prevent this from happening stagger drastic pruning over the course of three or four years, thus reducing the plant size gradually.


Deadheading Hydrangeas

Hydrangea

Spent flowers on mop-head hydrangeas can in mild areas of the UK be removed directly after flowering, but it is best to leave them on your plant over winter to provide some frost protection for the tender buds developing below. Remove the dead flower-heads in late winter or early spring, cutting back the stem to the first strong, healthy pair of buds down from the faded bloom.

Lace-cap are a more hardier variety of hydrangea and the faded blooms can be cut back after flowering has finished to the second pair of leaves below the head in order to prevent seed developing, which saps energy from the plant.


How To Take Hydrangea Cuttings

Propagating hydrangea cuttings is generally an easy task, but they are slow to root so it can be a problem getting them to over-winter unless they have developed a good root system. So the best time to take cuttings is in early summer, around July to give them the best head start in establishing a healthy root system.

  1. Take a cutting from a healthy stem of your hydrangea that is about 5-6” inches long, with at least three leaf nodes. Most experts recommend taking a cuttings from a stem that hasn’t flowered this year.
  2. Remove the lower leaves of the bottom two leaf nodes and trim the base just below the first leaf joint. The leaf node is where a leaf comes out of the stem. Most roots will form from this point.
  3. This should leave the top two leaves on the cutting, if the leaves are very large, you can cut them by half with sharp scissors.
  4. Dip the cutting in rooting hormone (this is entirely optional).
  5. Fill an 8” inch (20cm) deep pot (the pots need to be deep enough to accept the full length of the cutting stem), with one part sterile compost to one part sharp sand or horticultural grit.
  6. Using a dibber, make a deep planting hole in the compost, most of the cutting should be buried in the compost. Cover the pots with a little horticultural grit to improve surface drainage and prevent fungal growth.
  7. Water well and allow to drain. Place the cuttings in a damp shady spot. Remember hydrangeas are shade-loving so they don’t mind deep shade whilst rooting. Ideally place them in a gravel tray to ensure that plenty of moisture is available around the leaves.
  8. There is no real need to use a propagator or cover the pots with polythene, so long as you place the cuttings in a damp shady spot and not in bright sun.
  9. If the leaves wilt then spray them with tepid water on a regular basis until they perk-up.
  10. Hydrangea cuttings can take some time to root, so don’t be tempted to check for roots until new shoots and some top growth appears, usually after about 4 to 8 weeks.
  11. Once they have rooted well give them a regular feed with a general purpose liquid fertiliser.
  12. They can be potted-on at this stage but I usually keep them in their original pots until they are large enough to be planted straight out in the garden, in late summer or early autumn.
  13. If the cuttings have rooted late then sink the pots into the ground and cover with a little mulch to keep them snug until the spring. Don’t worry if the leaves fall off in winter as this is normal, they should sprout new shoots in the spring.

Hydrangea Facts

  • There are between 70 to 75 species of hydrangeas.
  • They are native to southern and eastern Asia (China, Japan, Taiwan, Korea, the Himalayas, and Indonesia) and the Americas. By far the greatest species diversity is in eastern Asia, notably China, Japan, and Korea.
  • Most are shrubs that grow to 3-9 ft, but some are small trees, and others are lianas that reach up to 100 ft by climbing trees.
  • They can be either deciduous or evergreen, though the widely cultivated temperate species are all deciduous.
  • Having been introduced to the Azores, Hydrangeas are now very common particularly on Faial Island, which is known as the “blue island” due to the vast number of hydrangeas present on the island.
  • Hydrangea is derived from Greek and means ‘water vessel’, which is reference to the shape of its seed capsules.
  • In Japan, ama-cha, meaning sweet tea, is another herbal tea made from the mountain hydrangea, whose leaves contain a substance that develops a sweet taste (phyllodulcin). For the fullest taste, fresh leaves are crumpled, steamed, and dried, yielding dark brown tea leaves.
  • Ama-cha is mainly used for kan-butsu-e (the Buddha bathing ceremony) on April 8 every year—the day thought to be Buddha’s birthday in Japan. During the ceremony, Ama-cha is poured over a statue of Buddha and served to people in attendance. A legend has it that on the day Buddha was born, nine dragons poured Amrita over him; ama-cha is substituted for Amrita in Japan.
  • In Korean tea, the mountain hydrangea is used for an herbal tea called sugukcha or ilsulcha.
  • The pink hydrangea has risen in popularity all over the world, but especially in Asia. Pink hydrangeas have many different meanings, but generally mean, “You are the beat of my heart,” as described by the celebrated Asian florist Tan Jun Yong, where he was quoted saying, “The light delicate blush of the petals reminds me of a beating heart, while the size could only match the heart of the sender!”.
  • The oak-leaved hydrangea was declared the official state wildflower of Alabama in 1999.

Conclusion

One of the nation’s favourite flowering shrubs is a pretty low maintenance and problemfree plant. If you remember to just literarily deadhead your hydrangea in spring if it produces its blooms on old wood, you will have flowers every summer on your hydrangea. And if the shrub planted in your garden produces flowers on new wood you prune it however much you wish in spring and it will still produce blooms that summer.

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