Hydrangeas how to prune

Pruning Hydrangeas: A Simple Guide

It’s technically autumn now which means, I know, don’t say it, winter is closing in. We’ve had a few cold spells in the past few weeks and some places have even had frost warnings. Fall isn’t a time to mope about the upcoming snow, slush, ice, and blistering cold winds: it’s harvest time, bird-watching time, and of course, pruning time.

Not all of our garden plants benefit from a yearly trim but some most definitely do. Take the iris for example: without a good haircut, your iris could be harbouring borers and fungus that will sit and wait for their time to strike.

Now let’s talk about hydrangeas: a garden beauty and a bit confusing when it’s time to prune. Do you or don’t you, that is the question.

What Variety Are You Growing?

There are three main varieties: hydrangea macrophylla, hydrangea arborescens, and hydrangea paniculata. If you don’t know what type you have, check your variety with this excellent reference guide: http://www.hydrangeashydrangeas.com/identify.html.

As a general rule though, pink, purple, and blue flowers indicate hydrangea macrophylla; Annabelle, Bounty, and Incrediball are all classified under the arborescens family; Limelight and PeeGee varieties are found within the paniculata variety.

Hydrangea Macrophylla

  • This variety can be left alone and not pruned at all, if you have no desire to get out pruning (although it is suggested that you prune old plants to allow space for new growth)
  • If you choose to prune, do it before August or you will be left with no blooms next year: hydrangeas set their buds in the summer the year before they are to bloom
  • Remove dead stems and prune for size when necessary

Hydrangea Arborescens

  • These are your Annabelles
  • Do not prune this type in the spring – this is a job best left for the fall
  • Heavy pruning (within a few inches of the ground) will not harm the plant but will cause stems to remain thin (the end result is a hydrangea that needs staking to hold up the large flower head in the early summer

Hydrangea Paniculata

  • The PeeGees and Limelight varieties
  • Prune these in the spring, fall, or winter but I would suggest pruning every other year to allow for strong stems
  • If pruning into a tree-form, prune out crossing branches and anything that you find unattractive
  • Again, if looking to form a tree, do not remove the main stem or your tree will be stunted and will grow out rather than up

Final Notes

Knowing what type of hydrangea you have is essential for pruning as some set their buds long before they will flower and some regenerate no matter how drastically we prune them back.

You’d be right in thinking this looks a bit of a mess. Poor Annabelle! This is her equivalent of a bad hair day.

The ‘Annabelle’ Hydrangea arborescens is one of the best flowering shrubs for a small city garden. Compact and somewhat shade tolerant, it performs well in an urban setting, producing a load of white pompom aka mophead flowers.

As with all hydrangeas, moisture does make it put on a better show. With all the rain last summer, ‘Annabelle’ was particularly happy in my garden. As usual, I left the drying heads over winter after flowering to catch the snow. About this time of year, though, she looks frazzled and badly in need of a haircut.

If you’re sure you have ‘Annabelle’, nothing could be easier, really. It makes its flowers on the current season’s wood. So late winter or early spring is the time to prune. Just look for the first set of fat new buds, as in the picture above, and prune back the stem to just above this new growth.

If you have a lusty plant and want to keep it contained, you can cut back drastically – almost to the ground – in late winter before the new growth appears. Or you can leave more of the main woody stem, as I do, to give the heavy heads more support in my shade-challenged garden. Cut any dead branches to the ground at any time; they’ll be brittle, so easy to identify.

When you’re finished, your shrub will look more like this. The stems will be about 18-24″ (50-60 cm) from the ground.

Be careful, though. Not all hydrangeas flower on new wood. If yours make pink or blue flowers, or if you have oakleaf hydrangeas (just as they sound, they have lobed, oakleaf-shaped leaves), these must be pruned differently, or you’ll lose the flower buds. And we don’t want that!

Have a look at the great site All About Hydrangeas by American Hydrangea Society member Judith King for info on different pruning requirements. She also gives you gives you a handy guide on identifying your hydrangeas so you know which is which.

So, now that your secateurs are nice and sharp, you know what to do with them.

It is used as follows:

  • the dung is spread under the outer area of the crown on the soil
  • if necessary, it can be covered with foliage
  • the dung should be spread in autumn or spring

Other organic substances such as compost, coffee grounds, horn meal and shavings as well as plant manure are also suitable fertilisers. They break down slowly and naturally and provide the hydrangea steadily with important nutrients. However, phosphorous universal fertilisers should not be used. When grown in a pot it should be kept in mind that the hydrangea needs more nutrients and therefore needs to be fertilised more often. Liquid hydrangea fertiliser which can me mixed into the water during spring and summer is the most suitable.

Cutting

If the hydrangea arborescens Annabelle is correctly cut back in late autumn or beginning of spring, growth and flowering in the next growing period is enhanced. As it grows quickly, it can be cropped generously.

You have to keep the following in mind when cutting the hydrangea arborescens Annabelle:

  • the hydrangea arborescens is cut back almost completely every year
  • all shoots that have grown in the past summer are cropped to short stubs
  • usually the plant is 15 cm high after cutting
  • on every stump two eyes remain

From these eyes new shoots grow for the following season. From every old shoot two new ones develop, which is why the hydrangea becomes bigger and boskier as it ages. If some branches grow too close and therefore impede each other, the plant should be thinned out a bit. Additionally, stunted and unwelcome shoots can be cut off during spring and summer. The hydrangea arborescens Annabelle is also very popular as a cut flower. Individual flowering shoots can be easily cut off and bundled for a flower bouquet.

Propping

It can happen that the big flower heads become too heavy for their shoots. It is not a problem if they sink slightly to the ground. Only when the branches are about to break you should take action. Affected flowers can be easily propped with a pole made of bamboo for example.

Hibernation

The hydrangea arborescens Annabelle is perennial and can easily overwinter outside. In regions with stronger frost the plant can be covered with pine brushwood after it has been cut back. A hydrangea arborescens Annabelle which is kept in a pot can also overwinter outside. Thereby, it is recommended that the pot is wrapped in a linen bag for example and put on a wooden pallet.

In this way, it is guaranteed that the substrate does not freeze completely. Only one-year-old young plants in a pot as well as plants in a pot with a diameter less than 30 cm need a frost-free wintering ground. This one should be bright and not warmer than 5°C.

Repotting

Tub plants as well as young plants that are kept in a pot can be repotted or planted outside in spring. As for most plants repotting is necessary when the pot becomes too small and no longer provides sufficient space for the roots.

Reproducing

The decorative flowers of the hydrangea are sterile, which is why the following forms of reproduction are especially suitable.

Cuttings

Cuttings are best derived the plant is cut back. One-year-old shoots are especially suitable as they are about 15 to 20 cm long and possess a minimum of two pairs of eyes. After the top of the shoot is cut off the cutting can be put in a pot with cultivation soil. The pot should be placed in a shady location.

The substrate needs to be kept wet constantly without waterlogging to occur. After two to three weeks the cutting begins to shoot and can be repotted into a pot, a tub or the garden in the following spring.

Layers

If the hydrangea arborescens Annabelle is to be reproduced in summer, this can be done with a layer. For this a flexible shoot is chosen which is only slightly lignified. It is put in a small hollow and covered with substrate. The top needs to be visible. A stone or a piece of wood can be put on the soil to fix the layer. As soon as a first shoot is visible the layer has developed its own roots. Now it can be cut off from the mother plant and planted separately at a desired place.

Allergy

The hydrangea contains glycoside. Some people react allergic against it and should touch only the plant with gloves. As it is poisonous, the hydrangea arborescens should not be eaten by humans nor animals.

Parasites

Aphids often infest the hydrangea arborescens. The few millimetre big insect can be seen with the naked eye. Moreover, they glue the leafs together with honeydew. In case of heavy infestation, the plant can be splashed with water and then sprayed with liquid manure extracted from stinging-nettle. Alternatively, a plant protection product can help.

Diseases

Mildew is the most common disease from which the hydrangea arborescens Annabelle suffers. There, the leafs and shoots are being covered with a white coat which spreads onto the entire plant little by little and thereby kills it. The mucus infests mostly hydrangea arborescens which are already weakened because of too little water or fertiliser. The infested parts need to be cut off generously. Afterwards the plant is treated with a protection product.

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There’s a lot of confusion about when to prune hydrangeas. You hear all sorts of advice: spring, fall, after they bloom, not at all, etc. And in fact, when you prune varies, depending especially on the species you’re growing. Here is a summary:

  1. Hydrangeas that Bloom on New Wood

These hydrangeas bloom on new growth that is produced in the spring. Therefore they can be pruned in late fall, after they finish blooming, or in early spring. However, since their dried flowers remain attractive all winter, it makes sense to prune them in early spring, just after snowmelt, rather than in the fall. After all, why prune off several month’s worth of beauty?

Note that pruning is never obligatory for these species. If you never prune them at all, or simply limit your pruning to deadheading (removing the faded flowers), they’ll still bloom well. And even if you don’t deadhead, note that the faded flowers will fall off all on their own when the plant begins to grow in the spring.

Three species are commonly grown:

PeeGee hydrangea (Hydrangea paniculata) Zone 3

PeeGee hydrangea

This hydrangea produces elongated clusters (panicles) of white flowers that turn increasingly pinker as fall advances. It’s is a very large shrub: most cultivars can reach 15 feet (5 m) in height and diameter if you allow them to grow entirely on their own.

With this shrub, pruning reduces the number of blooms, but gives larger flower clusters. If you want lots of flowers, prune little or not at all. If you want to keep the shrub more compact, prune back severely in early spring. If you prune it down to 6 inches/15 cm from the ground, by late summer you’ll get a compact plant about 3 to 4 feet (about 1 m) with extra-large panicles, although only a few of them. However, the wood won’t yet be fully developed and the stems can break under the weight of the blooms. A good compromise is cut it back annually back to about 3 feet (1 m) (still in early spring). This will give you a shrub about 5 to 6 feet (1.5-2 m) high with a decent amount of intermediate size panicles on stronger branches.

Smooth Hydrangea (H. arborescens) Zone 3

‘Annabelle’ smooth hydrangea

This shrub is easily recognized by its globes or domes of white flowers (there are now a few pink-blooming cultivars as well) which bloom at the tip of the stems starting in the middle of summer. ‘Annabelle’, with its very round balls of white flowers, is the best-known variety.

For very even bloom, giving branches all the same length, cut the plant down to 4 to 6 inches (10-15 cm) in early spring or late fall. However, this gives very large flower heads that tend to flop. If this happens under your conditions, a lighter pruning many help, removing only the top 6 inches (15 cm) of the plant. The resulting stems will be thicker and the flower clusters smaller, giving a stronger plant not so prone to flopping.

Climbing Hydrangea (H. anomala petiolaris), zone 4

This hydrangea is not like the others and rarely needs pruning. Remove only winter-damaged branches and any that wander where you don’t want.

  1. Hydrangeas that Bloom on Old Wood

These hydrangeas bloom from branches produced the previous year, although some cultivars bloom also bloom to a certain degree on new wood, giving a second flush of bloom. In colder climates, these hydrangeas require very careful pruning, mainly consisting of removing dead wood in the spring, at snowmelt. Even deadheading can harm the delicate flower buds that form just below the old flower head, so if you do prune after the flowers fade, make sure to prune just above a pair of healthy buds.

Bigleaf Hydrangea (H. macrophylla), zone 6b

Bigleaf hydrangea

Also called French hydrangea, mophead hydrangea (those with rounded flower clusters) or lacecap hydrangea (those with dome-shaped flower clusters), this hydrangea is renowned for flowers that can be blue in acid soils and pink in alkaline ones. I can be hard to grow in colder areas (north of zone 6) because of its limited hardiness. It’s best to try it in partial shade in rich, deep soil and in a sheltered spot protected from winter winds. In locations where snow cover is abundant and reliable, it may bloom well in zone 4 all on its own, but otherwise, it’s best to consider winter protection.

Winter protection for tender hydrangeas

This hydrangea suffers not only from winter cold, but also spring frosts. Even when it breezes through winter with no damage, it tends to sprout almost immediately in spring, leaving the growing flower buds subject to late frosts. To ensure bloom on this somewhat persnickety plant, winter protection is advised anywhere late spring frosts are possible. In the fall, after the leaves have fallen, surround the plant with a “cage” of chicken wire 1 to 2 feet (30-60 cm) high and fill it with dead leaves. Leave this leaf mulch in place until there is no longer any risk of frost: until late May or even early June in most colder climates. The mulch will keep the soil cold longer, delaying sprouting… and thus protecting the future flowers.

Only after you remove the mulch and the plant begins to grow should you consider pruning… and even then, remove only dead wood!

Mountain hydrangea (H. serrata), zone 5

Mountain hydrangea

This hydrangea is a near twin of the bigleaf hydrangea (H. macrophylla), but with thinner stems and smaller leaves. A little hardier than its cousin, it is theoretically winter-hardy to zone 5. Even so, its tender flower buds remain susceptible to damage from late frosts. In many climates, it is therefore wiser to give the cage-filled-with-fall-leaves treatment described above to ensure abundant bloom.

Oakleaf Hydrangea (H. quercifolia), zone 5

Oakleaf hydrangea

This hydrangea needs little pruning, except to remove any dead or damaged branches, including those damaged by winter cold. If you do need to perform heavy pruning, perhaps on an older specimen that has outgrown its allotted space over time, the best time to do so is in summer, immediately after flowering.

Hydrangea Pruning for the Laidback Gardener

A lot of the information above smacks of hard work, so you might wonder what I do myself, as a laidback gardener, when it comes to pruning hydrangeas. The answer is simple: I don’t prune them at all. And I don’t offer winter protection, either, because I only grown varieties adapted to my conditions. I just let them grow, that’s all. Life is so much easier that way!

To prune or not to prune? That is one of the quintessential gardening questions. Recently I asked a top landscaper in Virginia to weigh in on the issue. “When is the best time to prune hydrangeas without cutting off next year’s flowers?” I asked. Her reply?

“Never,” she said with a laugh. “But your best shot is after they’ve bloomed.”

It turns out that knowing how and when to prune hydrangeas involves first, identifying what kind of shrubs you own. And it all starts with determining whether they flower on old or new wood.

HYDRANGEAS THAT BLOOM ON OLD WOOD

Nikko Blue hydrangeas bloom on old wood

Old wood is quite simply, last year’s wood. Hydrangeas that bloom on old wood set their flower buds on stalks that have been on the plant since last summer. This generally occurs sometime in August, September or October.

Hydrangeas that bloom on old wood include the mophead, bigleaf (macrophylla), lacecap and oakleaf varieties.

Oakleaf hydrangea is recognizable by its foliage that resembles oak leaves

As a rule, these beautiful shrubs need little pruning. But if you must, knowing when and what to cut is key. Most importantly, the more old wood you take, the less of a floral display you’ll get next summer. Follow these three steps to maintain the health and vigor of your old wood hydrangeas:

  1. Immediately after flowering (and no later than July), remove flowering stems back to a pair of healthy buds.
  2. Prune out weak or damaged stems in late winter or early spring. Cut out no more than 1/3 of the oldest stalks, taking them down to ground level.
  3. Repeat the process every summer to rejuvenate the shrub and control its shape.

HYDRANGEAS THAT BLOOM ON NEW WOOD

Limelight hydrangeas bloom on new wood

Hydrangeas that bloom on new wood set their flowering buds on the current season’s growth. Because their flowers come from new growth from the base of the plant, they can be pruned almost any time of year, except summer. Follow these three steps to maintain the health and vigor of these types of hydrangeas:

  1. Cut off faded blooms in late summer to improve the looks of the shrub
  2. Prune out the oldest canes to improve vigor
  3. Cut back the entire shrub in late winter before new growth starts to appear

Additional tricks of the trade include leaving some of the older branches as a framework for new growth (these types of hydrangeas tend to open up and get floppy.) Many gardeners also advocate cutting the shrubs all the way back to the ground, which often produces bigger flowers.

HYDRANGEA ARBORESCENS ‘ANNABELLE’

Considered the crème de la crème of all the varieties that bloom on new wood, Hydrangea arborescens Annabelle is what is called a ‘smooth’ hydrangea. Smooth hydrangeas are known for their giant white blooms and are native to the southeastern United States.

Distinctive white blooms of Hydrangea ‘Annabelle’

What makes Annabelle so special is that it not only produces enormous, pure white flowers from June to August, but also stays compact, growing to just 3 to 5 feet tall and wide. At first glance, it can be hard to tell this cultivar apart from other white-blooming hydrangeas. However, a number of gardeners go by this golden rule: Annabelle flowers open lime green in early summer, change to bright white mid-summer and then switch back to light green in late summer before turning tan in the fall.

More recently, an improved version of Annabelle called Incrediball has been developed. It features basketball-sized blooms and thicker, sturdier stems that don’t flop over even if the flower heads become soaked with rain.

‘Incrediball’ features 12″ flower clusters and blooms on new wood

Pruning hydrangeas like Annabelle can help control for shape and increase blooms. For this reason, some gardeners cut the shrubs back to the ground (within 6″) in late winter or early spring. Some say this encourages them to produce the largest flowers and sturdiest stems. But others claim it weakens the plants over time, causing them to need to be staked.

I recommend taking the middle road and pruning Annabelles back to between 1 and 3 feet above the soil.

PANICLE HYDRANGEAS

Panicle hydrangeas bloom on new wood

Like Annabelles, panicle hydrangeas bloom on new wood. Since there’s no danger of cutting off blooms, they can be pruned in late winter or early spring before new growth. Cut them to the ground or to just a few feet above the soil depending on the size plant you want to maintain. The best known of the panicle hydrangeas include PeeGee and Limelight.

THE SUNNY WORLD OF LIMELIGHT HYDRANGEAS

When they were first introduced from Holland in the early 2000’s, Limelight hydrangeas took the garden world by storm. Featuring enormous, football shaped clusters of flowers, the shrubs performed great in full sun (although for best color, they require some shade).

Limelights keep their beautiful celadon color all summer long before aging slowly to pink. In the fall, they change to shades of dusty red and burgundy. Prune them like Annabelles.

Limelight hydrangeas bloom on new wood

ENDLESS SUMMER IS THE BEST OF BOTH WORLDS

There’s a new kind of hydrangea in town called Endless Summer and it’s rocking the hydrangea world. Introduced in 2004 by Bailey Nurseries, Endless Summer hydrangeas bloom on both old and new wood. As a result, this gives them the ability to flower repeatedly all summer. The company’s tag line is, appropriately,

Experience life in full-bloom.

Endless Summer mophead variety

As of 2018, there are three different varieties currently available. Blushing Bride produces pure white mophead flowers that mature to soft pink. Twist-n-Shout is the first re-blooming lacecap variety. And BloomStruck has vivid purple or rose-pink mophead blooms that hold their color all summer. Summer Crush (available in 2019) will feature raspberry red or neon purple blooms.

It’s easy to imagine the benefits of plants that bloom on both old and new wood. Their flowers naturally last for most of the summer. Moreover, the company says Endless Summer hydrangeas bloom 10 to 12 weeks longer than average hydrangeas. Best of all, these hydrangeas need little to no pruning.

SOME COMMONLY ASKED QUESTIONS ABOUT HYDRANGEAS

Why are my hydrangea flowers turning brown in the summer?

The main reason that mophead flowers turn brown is too much sun; specifically hot mid-day to afternoon sun. To prevent this problem, site your shrubs in areas where they receive direct sun either in the early morning or late afternoon. Same goes for the lacecap varieties, which tend to have a much shorter flowering span than the mopheads. Attention to watering during dry spells also helps prolong blooms.

What do I do if my hydrangeas have grown too big and floppy?

Most gardeners advise waiting until the shrubs have been in the ground for 5 years before beginning a pruning program. If you’ve got the type that blooms on new wood, prune your shrubs in late winter or early spring for shape, taking them down to between 1 and 3 feet from the ground. If you’ve got the kind that blooms on old wood, follow the method above, removing 1/3 of the oldest living stalks each summer after the shrubs have flowered.

When I cut blossoms will it hurt the other blooms?

After August, cut only short stems to avoid affecting next year’s blooms

For hydrangeas that bloom on old wood, deadheading (or cutting flowers for indoor arrangements) can be performed on long or short stems in June through July without affecting next year’s flower buds. After August, it’s best to harvest only short stems.

Can I prune some of the branches and not affect others?

Yes. You are only cutting off the flower buds on the stalks that you prune.

Does watering keep the blooms going? Why do my hydrangeas look so dry in July?

As with all plants, watering during dry spells is key. Keep the soil moist around your hydrangea shrubs to keep the flowers going all summer.

I did all the right things and my hydrangeas didn’t bloom this year. What happened?

Weather can negatively affect blooms, too

Finally, you can follow all the rules and prune your new or old wood shrubs correctly, but weather can also have its negative effects, particularly frost. In colder regions, flowering can be adversely affected by either early fall or late spring frosts, making it confusing as to whether you pruned off the blooms yourself or left it to Mother Nature.

Prune Hydrangea Bushes: Hydrangea Pruning Instructions

Since there are various types of hydrangea bushes, hydrangea pruning instructions may vary slightly with each. Although hydrangea pruning care differs, all hydrangeas can benefit from the removal of dead stems and spent blooms each year.

General Hydrangea Pruning Instructions & Deadheading Tips

Pruning hydrangea bushes is not necessary unless the shrubs have become overgrown or unsightly. You can safely remove spent blooms (deadhead) anytime. However, there are a couple deadheading tips to keep in mind for optimal results. Try to keep cuts above the first set of large leaves or only cut down to the last healthy buds. This ensures the safety of any developing blooms for the next season.

When pruning hydrangea bushes that have become overgrown, cut stems to the ground. Although this may delay blooming the following season, it helps revitalize the plants. All types of hydrangea respond well to occasional pruning, but it’s important to know what variety you have, as hydrangea pruning care varies.

Types of Hydrangea & Pruning Care

Understanding how to prune hydrangea bushes according to their particular type and individual needs is important for the overall health and vigor of hydrangea plants. Hydrangea pruning care techniques differ.

  • Big Leaf Hydrangea (H. macrophylla) includes the commonly grown mophead and lacecap varieties. When hydrangea pruning care should be performed for these sometimes varies. Generally, they are pruned in late summer, after blooming has ceased. However, some people prune them in fall while others do so in spring. As long as you do not cut any stems that have not bloomed, leaving healthy buds intact, they should be okay. Prune weak stems to the ground and cut or deadhead spent flowers and stems to the last bud.
  • Oakleaf Hydrangea (H. quercifolia) gets its name from the oak leaf shaped leaves. These hydrangeas are typically pruned in early spring, as their colorful fall foliage is oftentimes a welcomed sight in autumn. Many people also enjoy leaving the flower heads over winter for additional interest.
  • Pee Gee Hydrangea (H. paniculata), also known as Panicle, usually flowers on the current season’s growth. Therefore, they are generally pruned in late winter or early spring just before summer blooming. They can be pruned in fall as well. This type of hydrangea can also be pruned into a tree form, as it exhibits an upright growth habit.
  • Annabelle Hydrangea (H. arborescens) are usually pruned in the summer following spring blooming. Some people choose to prune them to the ground in late winter or trim dead growth in early spring just prior to blooming.
  • Climbing Hydrangea (H. anamala) often does not require pruning. Hydrangeas of this type produce flowers from side shoots, which can be pruned in fall after blooming has ceased. Cut back shoots to the last healthy bud.

When to prune hydrangea bushes varies and is not an exact science. Keep in mind that pruning hydrangea is not always necessary, and unless the situation calls for it, they can simply be left alone. Removal of spent blooms and dead stems each year should be adequate for maintaining healthy hydrangea bushes.

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