Hydrangeas: planting, pruning and care

Description and botany

Hydrangeas, called in Latin Hydrangea, are mainly bushes and include around fifty species, plus very many varieties! What gardeners usually mean by hydrangea most often refers to Hydrangea macrophylla, the species most widely cultivated. There are in fact more than 600 horticultural varieties of Hydrangea macrophylla.

Hydrangeas originate mainly from East Asia, although a few species occur in North America (for example Hydrangea arborescens…). Many species come from China, Japan and Korea. Hydrangea macrophylla, for instance, is native to Japan, but has naturalised in several regions worldwide (Central America, New Zealand…).

Hydrangea gives its name to family Hydrangeaceae (237 species), which also includes other ornamental plants such as Deutzia and Philadelphus. Some genera are very close to hydrangeas: Pileostegia, Schizophragma… Schizophragma are sometimes considered climbing hydrangeas!

Hydrangeas form bushes with a fairly broad, rounded habit. Most reach between 80 cm and 2 m in height. Some Hydrangea paniculata grow particularly tall (variety ‘Levana’, for example, reaches 3 m). Climbing hydrangeas (Hydrangea petiolaris and H. seemanii) are an exception, as they can reach 10–15 m! If you wish to grow hydrangeas in a pot, choose more compact varieties such as Hydrangea paniculata ‘Bobo’, or Hydrangea serrata…

Hydrangea macrophylla – botanical illustration

Hydrangeas are long-lived. In good growing conditions they can live for several decades, sometimes 50 years.

Hydrangeas generally flower throughout summer, from June until September–October. Those of the ‘Endless Summer’ series were selected for their very long flowering period!

They then produce large inflorescences made up of many flowers. These can be globular; flat (with all flowers on same level); or conical (Hydrangea paniculata). They form corymbs or paniculate clusters, often at stem tips, and can measure up to 15–20 cm across. Hydrangea inflorescences resemble those of some Viburnum!

Hydrangea arborescens are also valued for large inflorescences often creamy in tone (white–pale yellow, soft pink, pastel…): variety ‘Annabelle’, for instance, bears large white spheres that bend stems under their weight. Variety ‘Hayes Stardust’ has inflorescences up to 20 cm across made of small star-shaped flowers in creamy white to light green shades.

Some hydrangeas have very unusual flowers! Hydrangea macrophylla ‘Camino’, for example, surprises with inflorescences of rounded flowers with dentate edges. In ‘Hovaria Hopcorn’, sepals are rounded, incurved. Conversely, they are very fine and star-shaped in Hydrangea macrophylla ‘Princess Diana’ and ‘Stargazer’. Flowers can also be double, when each floret bears many sepals.

Inflorescences generally carry two types of flowers: large sterile flowers, very decorative, around periphery, and small fertile flowers, more discreet, at centre. In sterile flowers it is the enlarged sepals that are decorative; they look like petals. Fertile flowers bear many stamens. Horticultural varieties have been selected for large numbers of decorative sterile flowers.

Some hydrangeas have particularly vivid, extravagant blooms. Other times flowers are more delicate and natural. They can be very romantic, as in Hydrangea ‘You And Me Romance’…

Hydrangea flower colours are very attractive, often pink or blue. Flowers can also be white, red, mauve–violet, green… Sometimes bicoloured, as in Hydrangea macrophylla ‘Mirai’. Some varieties are remarkable for colour combinations, such as ‘Schloss Wackerbarth’.

Colours also tend to change with time, flowers sometimes taking green or pink–red shades. Colour change is very marked in some varieties, such as Hydrangea paniculata ‘Vanille Fraise’ (flowers first white and pink, then turning red), or hydrangeas of the ‘Magical’ series.

Different inflorescence forms: round-headed / flat-headed / paniculate

With Hydrangea macrophylla and Hydrangea serrata, flower colour has the particularity of changing according to soil pH: flowers turn blue in acidic soil and more pink in calcareous soil. It is therefore possible to slightly alter colour (to obtain blue) by adding, for example, aluminium sulfate in the form of alum, or crushed slate. White-flowering varieties do not change colour with pH.

Hydrangeas with blue flowers in acidic soil

Hydrangea flower colours therefore show great variability, depending on pH but also on season (early or late flowering).

Feel free to harvest flowers and dry them for dried bouquets! You can consult our advice sheet on how to dry hydrangea flowers.

Hydrangeas bear large leaves, often broad and ovate, measuring between 10 and 25 cm long. Species name macrophylla indeed means “large-leaved”. Leaf lamina margin is dentate. In Hydrangea quercifolia, leaves are lobed and resemble oak foliage, which gave the species its name (Quercus = oak in Latin).

Leaves are generally opposite (placed two by two on stems). They can also be inserted in threes (whorled).

Most cultivated hydrangeas are deciduous, except Hydrangea seemanii.

Usually hydrangea leaves are dark green. Foliage can also be variegated, as in Hydrangea petiolaris ‘Silver Lining’, with margins of white. Leaves are purple in Hydrangea macrophylla ‘Julisa’. As with flowers, hydrangea leaves can change colour at year end, taking fine autumn hues, especially in Hydrangea quercifolia! Variety ‘Snowflake’, for example, has leaves that turn purple late in season. Colour-wise, the most striking is perhaps hydrangea ‘Little Honey’, which bears superb golden-yellow foliage dazzling through season, then colouring orange–red in autumn!

Various foliage: Hydrangea macrophylla, Hydrangea quercifolia ‘Little Honey’, Hydrangea paniculata, Hydrangea petiolaris ‘Silver Lining’, Hydrangea macrophylla ‘Merveille Sanguine’

Stems are black in Hydrangea macrophylla ‘Nigra’ and ‘Zorro’, which highlights green foliage and flower colour.

Some hydrangeas are also villous, with more or less downy stems and leaves. This is the case in Hydrangea aspera, Hydrangea villosa and Hydrangea involucrata.

After pollination, flowers form capsules that open when ripe. These contain tiny seeds.

Beautiful autumn colours of Hydrangea quercifolia ‘Burgundy’ / Dark stems of Hydrangea macrophylla ‘Zorro’

Although hydrangeas are generally fairly hardy, some Hydrangea macrophylla varieties can be somewhat tender. The most cold-sensitive include varieties Hydrangea macrophylla ‘Mirai’ (-12°C) or ‘Leuchtfeuer’. Conversely, more resistant varieties include ‘Blueberry Cheesecake’, ‘Magical Noblesse’, ‘Ayesha’, and those of the ‘Endless Summer’ series. Among other hydrangea groups, Hydrangea serrata are particularly hardy. If you live in a cold-climate region and grow Hydrangea macrophylla, we recommend planting them near a west-facing wall. This will help them persist and flower well.

Discover Hydrangea paniculata in video with Olivier :

Main hydrangea varieties

Hydrangeas for shade and acidic soils

Hydrangeas for sun and ordinary soils

Hydrangeas for calcareous soils

Climbing hydrangeas

Hydrangeas suitable for container cultivation

These are Hydrangea macrophylla and Hydrangea serrata. They have a fairly ‘classic’ growing habit for hydrangeas: they like to be sheltered from direct sun and do well in soils with an acidic tendency. Hydrangea macrophylla are the most common hydrangeas, with large spherical inflorescences. H. serrata are smaller, offer delicate flowering, often flattened or domed, and are very hardy.

Hydrangea macrophylla Ayesha

Hydrangea whose flowers range from pale pink to soft blue depending on soil. Sepals are rounded and incurved, reminiscent of lilac flowers. It is an old, very hardy variety.

• Flowering time August to October
• Height at maturity 1,50 m

See the product sheet

Hydrangea macrophylla Endless Summer Bloomstar

Hydrangea offers very long summer flowering, from early summer until frosts. Flowers can range from pink to blue, depending on the soil in which it is grown.

• Flowering time July to November
• Height at maturity 1,70 m

See the product sheet

Hydrangea macrophylla Merveille Sanguine

Hydrangea ‘Merveille Sanguine’ bears large rounded inflorescences of a pronounced pink–red. Its foliage is dark, purple.

• Flowering time September to November
• Height at maturity 2 m

See the product sheet

Hydrangea serrata Blue Bird - Mountain Hydrangea

Hydrangea with flattened blue and white inflorescences. Fertile flowers are small, blue and positioned at the centre, surrounded by large, paler sterile flowers, mostly white.

• Flowering time August to October
• Height at maturity 1,20 m

See the product sheet

Hydrangea serrata Avelroz - Mountain Hydrangea

Hydrangea offers a delicate, soft luminous pink flowering. Inflorescences are flattened, with a profusion of small fertile flowers at the centre, surrounded by large sterile flowers. Its foliage takes on beautiful autumn colours.

• Flowering time July, August
• Height at maturity 1 m

See the product sheet

These are mainly Hydrangea paniculata. These hydrangeas produce large conical inflorescences, in panicles. They need sufficient light to flower well! Hydrangea arborescens and quercifolia can also grow in sun.

Hydrangea paniculata Vanille Fraise

Very popular, this paniculate hydrangea produces large conical inflorescences, the colour ranging from white to pink. They are borne on red stems.

• Flowering time August to November
• Height at maturity 2,50 m

See the product sheet

Hydrangea paniculata Limelight

This variety has large inflorescences initially green then white, which tend to become tinged with pink when autumn arrives. A very floriferous and bright variety.

• Flowering time August to November
• Height at maturity 2 m

See the product sheet

Hydrangea paniculata Great Star Le Vasterival

This variety bears large star-shaped flowers, pure white, composed of undulate sepals. A flowering appreciated for its elegance!

• Flowering time August to November
• Height at maturity 2 m

See the product sheet

Indeed, although Hydrangea macrophylla prefer acidic soils and dislike lime, this is far from true for all hydrangeas! In fact, Hydrangea arborescens and quercifolia will accept calcareous substrates. Hydrangea arborescens forms a shrub bearing large rounded inflorescences. Hydrangea quercifolia, for its part, is prized for its lobed foliage and lovely autumn colours.

Hydrangea arborescens Annabelle

This is our star variety, arguably the most popular! In summer this hydrangea bears a profusion of large inflorescences, about 30 cm in diameter, initially light green then pure white. It has been awarded the Award of Garden Merit by the Royal Horticultural Society (RHS).

• Flowering time July to October
• Height at maturity 1,50 m

See the product sheet

Hydrangea arborescens Pink Annabelle - Invicibelle

This hydrangea offers large spherical inflorescences, light pink. It is a very floriferous variety, with a fairly wide, spreading habit. It adapts well to growing in a pot.

• Flowering time July to November
• Height at maturity 1,50 m

See the product sheet

Hydrangea quercifolia Little Honey

This hydrangea is notable for its superb golden-yellow foliage! Its leaves are very attractively lobed, reminiscent of oak foliage. It produces a white, simple and delicate flowering. Avoid planting in full sun, as this could scorch its leaves.

• Flowering time September to November
• Height at maturity 1,50 m

See the product sheet

Hydrangea quercifolia Harmony

This variety bears large white inflorescences. This hydrangea also offers beautiful autumn colours, its foliage then taking on a red-purple hue.

• Flowering time August to November
• Height at maturity 2,50 m

See the product sheet

These are the petiolaris and seemanii hydrangeas. They offer white, fairly light and airy inflorescences, and have the advantage of being able to flower even in shade! You can plant them, for example, against a north-facing wall. They attach themselves using their climbing roots, and can climb very high!

Hydrangea anomala subsp. petiolaris- Climbing Hydrangea

This is a climbing hydrangea that offers a beautiful airy white flowering. It has been awarded the Award of Garden Merit by the Royal Horticultural Society (RHS).

• Flowering time July, August
• Height at maturity 4 m

See the product sheet

Hydrangea petiolaris Silver Lining- Climbing Hydrangea

This climbing hydrangea is notable for its foliage variegated with white, ideal for bringing brightness to a shaded spot. It also produces white flowers in summer.

• Flowering time June, July
• Height at maturity 3,50 m

See the product sheet

These are the most compact hydrangeas, reaching at most one metre in height.

Hydrangea paniculata Bobo

This hydrangea produces a profusion of cream-white flowers in summer, gathered in panicles. It is perfect for small spaces and prefers sunny positions.

• Flowering time September to November
• Height at maturity 70 cm

See the product sheet

Hydrangea serrata Shôjo - Mountain Hydrangea

Hydrangea ‘Shojo’ bears composite inflorescences with many small dark-blue flowers at the centre and larger paler flowers on the outside. Its foliage takes on beautiful autumn colours. Place it in shade or semi-shade, sheltered from the sun during the hottest hours.

• Flowering time July to September
• Height at maturity 1 m

See the product sheet

If you still have difficulty deciding among all these varieties, do not hesitate to consult our factsheet Hydrangeas – How to choose them?

Planting hydrangeas

Where to plant?

Most hydrangeas, notably Hydrangea macrophylla and serrata, prefer semi-shade, sheltered from sun during hottest hours of afternoon! Climbing hydrangeas are perfect for planting on a north-facing wall. Also avoid sun for hydrangea ‘Little Honey’: its golden foliage could scorch. Hydrangea paniculata and arborescens, on the other hand, enjoy sun!

Hydrangea serrata ‘Veerle’

Plant hydrangeas in soil that stays cool in summer. Most species dislike drought. Hydrangeas appreciate soils rich in organic matter, fertile. They like light, well-aerated soil. They will thrive in soil similar to woodland topsoil, found naturally in forests. They will do less well if planted in compact soil.

As a rule, hydrangeas do not like markedly calcareous soil, which causes chlorosis (yellowing of leaves). They prefer slightly acidic or neutral soils. If your soil is calcareous, you can grow them in pots, or dig a wide planting hole and fill it with potting compost, which you can mix with a little heather soil. However, Hydrangea paniculata, arborescens, quercifolia and sargentiana tolerate limestone well (read our advice sheet on this subject Hydrangeas on calcareous soil, it’s possible!).

It is preferable to place hydrangeas in a spot sheltered from wind. Choose a slightly sheltered position (for example, against a wall). The plant will then be less vulnerable to late spring frosts.

You can place hydrangea at back of a border, in a hedge, at an edge… Planting in a pot is also a good solution to adorn a patio or courtyard. In that case choose Hydrangea paniculata ‘Bobo’, or Hydrangea serrata, which have a rather compact habit. Climbing varieties are perfect for dressing a north-facing wall.

→ Also discover our video: Drought-resistant hydrangeas.

When to plant?

Hydrangeas are preferably planted in early autumn, around September, but planting can also be done in spring, after last frosts.

Hardier species can also be planted in winter or summer, provided periods of frost or hot spells are avoided.

How to plant?

Keep at least one metre between two hydrangeas, although this also depends on variety chosen.

1. Place rootball in a basin filled with water. This allows proper rehydration and makes subsequent watering easier.
2. Meanwhile, dig a planting hole. It should be about three times the size of the rootball.
3. Add organic matter: well-rotted compost or manure, organic fertiliser (crushed horn, dried blood…). If you grow Hydrangea macrophylla, you can also add a little heather soil (especially if you want blue flowers, or if your soil is calcareous).
4. Remove plant from its pot.
5. Rake bottom of the rootball to loosen the roots slightly.
6. Place plant in the planting hole, collar level with soil surface, then firm down lightly.
7. Water generously.

Planting a hydrangea

As hydrangeas appreciate soil that stays cool, it is always best to apply a layer of organic mulch at their base: choose, for example, BRF, fallen leaves, pine bark… Also, water regularly for several weeks after planting.

Hydrangeas can very well be grown in pots and tubs; for all details, consult our advice sheet: “Hydrangea in a pot: planting and care”

Hydrangea paniculata ‘Vanille Fraise’ grown in large barrels ( ©Biosphoto – Friedrich Strauss)

Caring for hydrangeas

Hydrangeas need soil to remain relatively cool. Water during summer, especially in dry spells. Be vigilant, particularly in first year or when growing in a pot (potting mix dries out more quickly). Avoid using hard water; prefer rainwater. Also beware of excess moisture: hydrangeas do not like standing water, which may encourage disease.

Inflorescence of a withered hydrangea

We recommend applying some well-rotted compost at the base of your hydrangeas in spring, to enrich soil. Incorporate it into soil by lightly scratching surface with a hand fork. You can also add horn meal or blood meal. However avoid excess fertiliser or organic matter, as this can encourage plant to produce lots of foliage at expense of flowering.

Similarly, it is preferable to always keep a layer of mulch at the base of the bush, as this helps soil remain cool while limiting weed growth… And as it decomposes, this mulch will enrich soil. Use for example ramial chipped wood or dead leaves, to a depth of at least 5 cm.

If you grow your hydrangea in a pot, remember to repot from time to time. You can do this every two years, at beginning of spring.

When inflorescences are withered, it is best to leave them in place over winter, as they will protect stems from cold. Cut them only at start of spring.

To keep blue flowers on your hydrangeas, you can occasionally add alum or crushed slate. We explain more in our article : How to get a blue hydrangea in the garden?

If you need to transplant a hydrangea, consult our video tips :

How to prune hydrangeas?

Pruning encourages generous flowering and helps plant maintain a balanced, harmonious shape. You can prune hydrangea each year in March–April. Carry out very light pruning on Hydrangea macrophylla and H. serrata, removing mainly dead wood, damaged branches and withered inflorescences. If you prune too short you may compromise flowering, because flower buds form at tips of stems. You can also thin and aerate centre of bush by removing some branches. Prune more severely Hydrangea paniculata and arborescens: cut back previous year’s branches, cutting just above healthy buds. We also recommend fairly light pruning for climbing hydrangeas. When pruning, always prioritise removal of damaged, malformed or dead branches.

For full details on pruning hydrangeas, see our advice sheets : When to prune hydrangeas? and How to prune hydrangeas?

Also see Tips to protect hydrangeas in winter

Also see our videos : How to prune Hydrangea macrophylla and Hydrangea paniculata

Hydrangea diseases and parasitic problems

Hydrangeas can be affected by several diseases. Take particular care with Botrytis cinerea, a fungal disease also known as grey mould and favoured by heat and humidity. They can also be affected by powdery mildew, which appears as a white, felt-like coating on leaves. For both these fungal diseases, treat using a sulphur-based solution.

Hydrangea leaf affected by powdery mildew

Regarding pests, hydrangeas are particularly susceptible to attacks by cottony cushion scale (Pulvinaria hydrangeae). These are small elongated insects with a white, cottony appearance. If not too numerous, you can remove them with a cloth soaked in soapy water. Aphids also sometimes attack hydrangeas. They pierce leaves and feed on sap, which weakens the plant. To get rid of them, use black soap. You may also encounter problems with red spider mites. As these dislike humidity, simply spray water onto foliage.

If substrate is too calcareous, hydrangea may suffer from chlorosis. Foliage discolours, becoming yellow between veins. Plant is deficient: calcium present in soil blocks plant’s iron uptake. Use iron chelate (readily absorbed), or consider growing the plant in a pot, in a mix of potting compost and heather soil.

Propagation

Best technique to multiply hydrangeas is propagation by cuttings. It is also possible to sow seeds in late winter, but this method is slower and more difficult. Climbing species are usually propagated by layering.

Propagation by cuttings

Hydrangeas multiply very well by propagation by cuttings! This technique is fairly easy. Prefer to do it in late summer, around August, on semi-woody stems.

1. Choose a healthy young stem (that grew during the year), not flowering, and cut it using pruning shear, just below a node (leaf insertion point). It should measure about 15 cm in length and carry at least three pairs of leaves.
2. Remove leaves from the base, leaving only two or three leaves. If those at the top of the cutting are large, trim them in half.
3. Prepare a pot with potting compost, then water to moisten it.
4. Optionally dip the base of the stem in plant hormone.
5. Make a small hole in the substrate using a small cane or a pencil.
6. Plant the cutting, and firm the substrate around it to remove air pockets.
7. You can cover the pot with a plastic bag to retain high humidity (enclosed propagation).
8. Then place in a sheltered warm spot, without direct sunlight.

Keep substrate slightly moist until cutting starts growth.

→ Learn more about hydrangea cutting in our tutorial!

Discover our video tips – How to propagate a hydrangea :

… as well as our advice sheet: Getting good cuttings from climbing hydrangea Hydrangea petiolaris

Pairing hydrangeas in the garden

Since Hydrangea macrophylla and Hydrangea serrata are rather suited to shady spots, they will easily find a place in a woodland garden. Plant them, for example, with foxgloves, Paris polyphylla, hostas, Geranium nodosum, ferns and Thalictrums. Also consider Brunnera macrophylla, which offer superb foliage and very delicate, charming flowering. Create a shady, cool corner with a fairly natural style. Although at first glance the large inflorescences of hydrangeas can seem “artificial” and exuberant, some varieties have more delicate flowerings and can perfectly fit into a fairly natural, wild-looking border.

In sun, you can use Hydrangea paniculata to compose a colourful border, with perennials and long-flowering bushes. Place hydrangeas towards the back, and put nepetas, Verbena bonariensis, echinaceas, Achillea, hardy geraniums in front. This will give you a flowering border throughout summer. Feel free to scatter some ornamental grasses (Stipa, Pennisetum, Briza media …) to add lightness and movement.

An idea for a sunny combination: Rudbeckia fulgida ‘GoldSturm’, Miscanthus sinensis ‘Zebrinus’ and ‘Gracillimus’, Pennisetum alopecuroides ‘Hameln Gold’, Hydrangea paniculata ‘Limelight’

As Hydrangea macrophylla prefer rather acidic soils and shady spots, you can plant them with other species that will enjoy the same conditions, such as azaleas, camellias, Pieris or skimmia. Add a few ferns if desired.

Hydrangeas can be incorporated into a romantic garden. Pair them with other plants with delicate flowerings, such as astrantias, gypsophilas or foxgloves. For hydrangeas, you might choose a variety such as ‘You and Me Romance’, which offers a very romantic flowering. Varieties with white flowers also suit this style of garden.

An example of a romantic combination: Hydrangea arborescens ‘Annabelle’, Agastache ‘Black Adder’, Veronicastrum virginicum var abum, Angelica gigas, Veronica spicata ‘Alba’, Nepeta faassenii ‘Six Hills Giant’

Because they offer lush foliage and delicate, generous flowering, often in blue or white tones, hydrangeas are perfect for a cottage garden! Plant them with delphiniums, oriental poppies, cosmos, hardy geraniums… The aim is a border that is both wild and abundant, with a profusion of flowers opening in soft, pastel tones.

Finally, you can pair Hydrangea quercifolia with other plants that take on beautiful autumn colours: maples, dogwoods, Nandina domestica…