Ornamentalshrub ornamentalStraightforward

Hydrangea

Hydrangea macrophylla

The shrub whose flower colour follows the soil, which is the most-asked ornamental question in Britain and the most often mis-stated. It applies to mophead and lacecap hydrangeas only, it works in one direction far more easily than the other, and it does nothing at all to a white cultivar.

Position: Partial shade or Dappled shade
Water: high demand
Drainage: Moisture-retentive
Grows to: 100–200 cm × 100–250 cm
Hardiness: H5
Flowers: July to September
Difficulty: Straightforward

Described view

The same hydrangea cultivar flowering blue on acid soil and pink on alkaline soil, side by side, with a white cultivar showing no change

August

In flower

Coming next month: plant.

Hydrangea’s year

Resolved for United Kingdom (general). Every window is stored against a climate event rather than a date, so a late frost pocket runs later than the band shows. What else August calls for.

Activity	M	A	J	A	S	O
Plant	March.	April.			September.	October.
In flower			July.	August.	September.
Prune	March.	April.

Timing that travels

The band above resolves this plant's windows into months for one region. These are the windows themselves, stored against a climate event rather than a date — which is the form that survives being carried to a colder garden, a frost pocket, or next year.

Conditions it needs

Light: Partial shade, Dappled shade
Frost: Hardy
Hardiness rating: H5 (RHS)
Grows best at: 15–24 °C
Soil: Loam, Clay
Soil pH: 5–7
Drainage: Moisture-retentive
Water needs: high
Drought: poor tolerance
Waterlogging: moderate tolerance
Heat: poor tolerance
Wind and exposure: poor tolerance

Where these figures come from

LightSourced guidancemoderate confidence

Royal Horticultural Society: Hydrangea — position

Checked 2026-08-13

FrostSourced guidancehigh confidence

Royal Horticultural Society: Hydrangea — hardiness

Checked 2026-08-13

Hardiness ratingSourced guidancemoderate confidence

Royal Horticultural Society: RHS hardiness ratings

Checked 2026-08-13

Grows best atSourced guidancemoderate confidence

Royal Horticultural Society: Hydrangea — temperature

Checked 2026-08-13

SoilSourced guidancemoderate confidence

Royal Horticultural Society: Hydrangea — soil

Checked 2026-08-13

Soil pHSourced guidancemoderate confidence

Plant Finder — Missouri Botanical Garden: Hydrangea macrophylla — culture

Checked 2026-08-13

DrainageSourced guidancemoderate confidence

Royal Horticultural Society: Hydrangea — soil

Checked 2026-08-13

Water needsHorticultural consensusmoderate confidence

The name comes from the Greek for water. It shows stress fast.

No external citation — see the evidence type above.

Checked 2026-08-13

DroughtHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

WaterloggingHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

HeatHorticultural consensusmoderate confidence

Wilts visibly in full afternoon sun even when the soil is moist.

No external citation — see the evidence type above.

Checked 2026-08-13

Wind and exposureHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

On your soil

Computed by comparing this plant's recorded requirements against each soil's recorded characteristics. A recorded horticultural fact overrides the comparison where GrowingHQ holds one.

Soil	Verdict	Why
Heavy clay	Prefers this soil	Heavy clay suits Hydrangea as it stands: The pH suits it: it wants 5 to 7, and this soil is in that range. Clay is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Sandy	Works, with one condition	Hydrangea will crop on sandy, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Chalky and alkaline	Struggles here	Hydrangea struggles on chalky and alkaline: The soil is substantially too alkaline for it: it wants pH 5 to 7, and this soil sits around 7.8 to 8.5. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering. A container or a raised bed of imported soil sidesteps the problem entirely.
Loam	Prefers this soil	Loam suits Hydrangea as it stands: The pH suits it: it wants 5 to 7, and this soil is in that range. Loam is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Silty	Grows well here	Hydrangea grows perfectly well on silty without special measures, though it is not the soil it would choose.
Peaty and acid	Grows well here	Hydrangea grows perfectly well on peaty and acid without special measures, though it is not the soil it would choose.
Shallow over rock	Works, with one condition	Hydrangea will crop on shallow over rock, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Made ground and urban soil	Grows well here	Hydrangea grows perfectly well on made ground and urban soil without special measures, though it is not the soil it would choose.

Not sure which you have? Four hand tests will settle it.

Space and spacing

Mature height: 100–200 cm
Mature spread: 100–250 cm
Rooting depth: 50 cm
Spacing: 120–180 cm apart

Where these figures come from

Mature heightHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Mature spreadHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Rooting depthHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
SpacingSourced guidancemoderate confidence: Royal Horticultural Society: Hydrangea — spacing
Checked 2026-08-13

Measured centre to centre. Plants set closer than this compete for light and water long before they look crowded, and the crowding cannot be undone once they are in.

In a container

Minimum volume: 30 litres or more
Minimum depth: 35 cm

Where the container figures come from

Minimum volumeHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Minimum depthHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

A good container plant provided it is never allowed to dry out, which in practice means daily watering in summer and a shaded position for the pot itself. Loam-based compost holds moisture far better than multipurpose.

Habit and ultimate size

What the plant becomes, rather than what it is when you buy it. The gap between the two is where most planting mistakes live.

Foliage: Deciduous
In a container: Good in a container long-term

Where these figures come from

FoliageSourced guidancehigh confidence: Royal Horticultural Society: Hydrangea macrophylla — foliage
Checked 2026-08-13
In a containerHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

Growth rate: Moderate — roughly 30–60 cm a year
Ultimate height: 100–200 cm
Ultimate spread: 100–250 cm
Time to reach it: 10–15 yearsSourced guidance

Where these figures come from

Growth rateSourced guidancemoderate confidence: Royal Horticultural Society: Hydrangea macrophylla — growth rate
Checked 2026-08-13
Ultimate heightSourced guidancemoderate confidence: Royal Horticultural Society: Hydrangea macrophylla — ultimate height
Checked 2026-08-13
Ultimate spreadSourced guidancemoderate confidence: Royal Horticultural Society: Hydrangea macrophylla — ultimate spread
Checked 2026-08-13
Time to reach itSourced guidancelow confidence: Royal Horticultural Society: Hydrangea macrophylla — time to ultimate size
Checked 2026-08-13

Cutting it back. Cut out a third of the oldest stems at the base each spring rather than shearing the whole plant over. Mophead and lacecap hydrangeas flower on wood made the previous year, so an all-over trim in spring removes the entire season's flowers.

source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Where and how you can grow it

Each way of growing is assessed separately, and “not assessed” is a real answer rather than a gap we have filled in with a guess.

Method	Suitability	What it needs
Open ground	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Traditional dug bed	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Raised bed	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Container	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13	30 litres; Reliable watering — it will not forgive a dry fortnight
Hydroponics	Not suitable source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13

Growing it

FeedingBlue flowers require acid soil, roughly pH 5.5 or below, where aluminium is available to the plant; above about pH 6.5 the same cultivar flowers pink. Making an acid soil alkaline is easy; making an alkaline soil reliably acid is not, so a blue hydrangea on chalk is a container of ericaceous compost rather than a soil project. White cultivars do not change colour at any pH.
PruningCut back to the first strong pair of buds below each faded head in spring, and take out a couple of the oldest stems at the base. Mophead hydrangeas flower on wood made the previous year, so a hard cut in spring removes the flowers.
WateringThe name means water vessel and the plant means it. Hydrangeas are shallow-rooted and wilt visibly on hot afternoons even in moist soil; the test is whether they have recovered by the following morning, and if they have not, the soil is genuinely dry. Water thoroughly at the base and mulch, particularly for plants in containers or under the rain shadow of a wall.
MulchingMulch generously every spring with garden compost, leaf mould or well-rotted manure, keeping it off the stems. This is the single most useful thing done for a hydrangea in a British garden and it is doing the watering job rather than the feeding one — the roots are shallow and spreading, the leaves are large and lose water fast, and a mulched plant wilts far less in July than an unmulched one in the same border. Do not mulch with mushroom compost, which is limy and will shift a blue hydrangea towards pink.

Where this guidance comes from

FeedingSourced guidancehigh confidence: Royal Horticultural Society: Hydrangea — flower colour
Checked 2026-08-13
PruningSourced guidancehigh confidence: Royal Horticultural Society: Hydrangea — pruning
Checked 2026-08-13
WateringSourced guidancehigh confidence: Royal Horticultural Society: Hydrangeas — watering
Checked 2026-08-13
MulchingSourced guidancemoderate confidence: Royal Horticultural Society: Hydrangeas — cultivation
Checked 2026-08-13

The bud you cut to becomes the new shoot, and it grows in the direction it points — which is why an outward-facing bud opens the plant up and an inward-facing one crosses the middle.

What goes wrong

Problem	How often	Notes
Capsid bug	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Pruned at the wrong time	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	Autumn deadheading takes next summer's buds; leave the heads on until spring.
Powdery mildew	occasional source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13

Start from what you can see

Crisp brown edges around the leaf margin

Sources for this page

GrowingHQ editorial synthesis · Plant Finder · Royal Horticultural Society

Each figure on this page carries its own citation, under the “where these figures come from” note in its section. Record last reviewed 2026-08-14.

If something is wrong with it

Holes eaten in leaves — 3 causes GrowingHQ holds for hydrangea
Lower leaves turning yellow — 2 causes GrowingHQ holds for hydrangea

Something else? Work through it with the diagnostic tool.