How do I make my hydrangea flowers blue (or pink)?

Only works on H. macrophylla mophead and lacecap types. For blue: soil pH must be acid (4.5–5.5). Add aluminium sulphate or specialist hydrangea blueing agent twice a year (March and September). Ericaceous compost in pots. For pink: soil pH alkaline (7+). Add garden lime annually. White-flowered cultivars (Annabelle, Limelight, Vanille Fraise) don't change colour regardless of pH. Paniculata and arborescens types are not pH-sensitive.

When and how should I prune my hydrangea?

Crucial — depends entirely on type. Macrophylla (mophead/lacecap): light prune in March, removing only spent flowers and weak stems. Flowers on last year's wood, so heavy pruning loses next year's flowers. Paniculata: hard prune each March to a permanent framework 30 cm above ground. Flowers on this year's wood, so heavy pruning is what makes it flower. Arborescens (Annabelle): all stems to 30 cm each March. Wrong pruning for type is the single biggest cause of hydrangea problems.

Why is my hydrangea not flowering?

Most likely: wrong pruning for the type, or late frost damage to flower buds in spring. Macrophylla pruned hard like a paniculata loses all flower buds. Other causes: too much shade, too little water, over-feeding with nitrogen, or a young plant not yet established. Patience for new plants — they often skip a year while settling in.

What's the difference between mophead, lacecap, and paniculata hydrangeas?

Mophead (macrophylla): rounded heads of densely-packed sterile flowers — the classic. Pink, blue, white. Flower on last year's wood. Lacecap (macrophylla): flat heads of small fertile flowers ringed by larger sterile ones. Same plant, different flower form. Paniculata: cone-shaped flower heads — Limelight (lime-green), Vanille Fraise (white turning pink). Flower on this year's wood; pruned hard. Arborescens (Annabelle): basketball-sized round white heads. Flower on this year's wood; pruned hard.

Can I grow hydrangeas in containers?

Yes — H. macrophylla compact cultivars (Cityline series, You & Me, Endless Summer) and dwarf paniculatas (Bobo, Little Lime) suit large containers. Use 40-litre pots minimum, peat-free compost (ericaceous if maintaining blue mopheads), water daily in summer. Container hydrangeas need feeding more than ground plants — a slow-release granular feed in March and again in June.

How do I dry hydrangea flower heads?

Pick mature heads in autumn when they've turned slightly papery to the touch — usually September or October. The petals should feel papery, not soft and fresh. Cut stems 30–40 cm long; remove leaves; hang upside down in a cool dark airy place for 2 weeks. Dried hydrangeas keep their shape for 1–2 years; colours fade but the overall effect is beautiful in winter arrangements.

Hydrangea — Grow

Hydrangea

shrub

About

Plant hydrangeas in spring or autumn in moist, fertile soil with part-shade or sun for half the day. Hydrangeas are hardy (RHS H5) and one of the most rewarding flowering shrubs for UK gardens. Hydrangea macrophylla (mophead and lacecap) is the classic — flower colour shifts with soil pH (acid = blue, alkaline = pink). H. paniculata (Limelight, Vanille Fraise) gives huge cone-shaped flower heads regardless of pH. H. arborescens (Annabelle) produces basketball-sized white flowers on new growth. Each type has different pruning needs — and most hydrangea failures are bad pruning, not bad sites. Water deeply through summer; mulch heavily; feed in March. Pick fresh for vases or dry the heads for winter arrangements.

How to grow hydrangea

1
Identify your hydrangea type
Mophead and lacecap (H. macrophylla); paniculata (H. paniculata); arborescens (H. arborescens); oakleaf (H. quercifolia); climbing (H. anomala subsp. petiolaris). Each needs different pruning, and confusion is the commonest reason for poor flowering.
2
Plant in a partly-shaded spot
Morning sun, afternoon shade is ideal in most of the UK. Full sun is fine in cool maritime gardens. Avoid deep shade — flowering reduces sharply. Macrophylla types tolerate more sun than paniculata in the south.
3
Plant in moist, fertile soil
Fork in well-rotted compost or leaf mould. Hydrangeas drink heavily — moisture-retentive soil is essential. Heavy clay improved with grit works; light sandy soil needs lots of organic matter to hold water.
4
Adjust soil pH for mophead colour (if you want)
H. macrophylla mophead flower colour shifts with soil pH. Acid soil (pH 4.5–5.5): blue flowers. Alkaline soil (pH 7+): pink. To turn pink mopheads blue, apply aluminium sulphate or specialist hydrangea blueing agent twice a year. To turn blue to pink, add lime. Some cultivars (Vibrania) are bred for set colours and don't shift. White mopheads stay white regardless.
5
Prune by type
Macrophylla (mophead/lacecap): light prune in March. Cut spent flowers back to the next fat pair of buds; remove weak or crossing stems at the base; that's all. Paniculata: cut back hard each March — to a permanent framework 30 cm above the ground. Flowers on this year's growth. Arborescens (Annabelle): cut all stems to 30 cm each March. Flowers on this year's growth. Oakleaf and climbing: light prune only after flowering; flowers on last year's wood.
6
Water deeply through summer
Hydrangea leaves wilt dramatically in drought — the plant looks like it's dying. Water deeply twice a week through July and August. Mulch heavily with compost to hold moisture. Containers need daily watering in hot weather.
7
Feed in March
A balanced shrub feed in March. Ericaceous formula if you're maintaining blue mophead colour (the soil chemistry stays right longer). Don't over-feed — pushes leaves at the expense of flowers.
8
Dry flowers for arrangements
Pick mature flower heads in autumn when they've turned papery (usually September–October). Hang upside down in a dry place for 2 weeks. Dried hydrangea heads keep their shape and colour for 1–2 years.

Common questions

The hydrangea year in your garden

Dispatching imaginary bots to check your garden out...

What to do now

Hardiness Zones

H1a (tender)H7 (very hardy)

H1a

H1b

H1c

RHS H5–H6

USDA 6 equivalent