Most hydrangeas in UK gardens are macrophylla, but the four types have quite different pruning needs — getting this wrong is one of the most common ways people accidentally cut off a whole year's flowers.
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Does it climb by itself, clinging to a wall or tree with small aerial roots, like ivy — rather than growing as a free-standing bush?
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If you are still unsure
If you can't tell macrophylla from arborescens (both can look like rounded mopheads), check the old flowerheads over winter: macrophylla leaves last year's brown flowerheads on woody stems that stay upright, while arborescens stems are softer at the base and the whole plant flops when heavy with rain or old flowerheads. If genuinely still unsure, treat it as macrophylla and only deadhead/lightly tidy in spring rather than cutting hard — paniculata and arborescens tolerate that light touch fine even though they could take a harder prune, but macrophylla can't afford to lose the old wood.
COMMON MISTAKE
Hard-pruning a macrophylla in late winter or spring like a paniculata or arborescens removes the old wood carrying that year's flower buds — the single most common way a hydrangea 'stops flowering' after a keen winter tidy-up.
Already know the variety name?
The name on the label tells you the type.
Hydrangea macrophylla ‘Endless Summer’Macrophylla › · One of the first macrophylla cultivars bred to rebloom on new growth as well as old wood; blue in acid soil, pink in alkaline soil.
Hydrangea macrophylla ‘Nikko Blue’Macrophylla › · Classic mophead, vivid blue in acid soil, large rounded flowerheads.
Hydrangea macrophylla ‘Ayesha’Macrophylla › · Unusual mophead with cupped, scented petals that look almost like a lilac.
Hydrangea macrophylla ‘Générale Vicomtesse de Vibraye’Macrophylla › · Historic mophead cultivar, pink or blue depending on soil, still widely sold.
Hydrangea macrophylla ‘Madame Emile Mouillère’Macrophylla › · White mophead, sometimes edged pink, one of the oldest cultivars still commonly sold.
Hydrangea macrophylla ‘Mariesii Perfecta’Macrophylla › · Lacecap type — a ring of large sterile flowers around a flat centre of tiny fertile ones, blue or pink depending on soil.
Hydrangea paniculata ‘Pinky Winky’Paniculata › · White ageing to deep pink from the base up, giving a distinctive two-tone cone.
Hydrangea paniculata ‘Little Lime’Paniculata › · Compact form of 'Limelight', well suited to a smaller garden or a large pot.
Hydrangea paniculata ‘Grandiflora’ (PeeGee)Paniculata › · The original, very old and vigorous paniculata cultivar, sometimes trained as a small standard tree.
Hydrangea arborescens ‘Annabelle’Arborescens › · Huge white globe-shaped flowerheads, the classic and most widely grown arborescens; tends to flop over when the heads get heavy with rain.
Hydrangea arborescens ‘Incrediball’Arborescens › · Like 'Annabelle' but bred with stronger stems that hold the huge white heads upright.
Hydrangea arborescens ‘Invincibelle Spirit’Arborescens › · The first pink-flowered arborescens cultivar, otherwise similar habit to 'Annabelle'.
Hydrangea anomala subsp. petiolarisPetiolaris › · Climbing hydrangea — self-clinging by aerial roots like ivy, white lacecap flowers, the plant almost always sold simply as "climbing hydrangea".
Hydrangea petiolaris ‘Miranda’Petiolaris › · Variegated-leaf selection of climbing hydrangea, leaves edged in cream.