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.

Hortensia

Hydrangea

Plantez les hortensias au printemps ou à l'automne dans un sol humide et fertile, à mi-ombre ou au soleil pendant la moitié de la journée. Les hortensias sont rustiques (RHS H5) et comptent parmi les arbustes à fleurs les plus gratifiants pour les jardins britanniques. L'Hortensia macrophylla (à tête ronde et à capuchon) est le plus classique : la couleur de ses fleurs varie en fonction du pH du sol (acide = bleu, alcalin = rose). H. paniculata (Limelight, Vanille Fraise) produit d'énormes capitules en forme de cône, quel que soit le pH. H. arborescens (Annabelle) produit des fleurs blanches de la taille d'un ballon de basket sur les nouvelles pousses. Chaque variété a des besoins différents en matière de taille — et la plupart des échecs avec les hortensias sont dus à une mauvaise taille, et non à un emplacement inadapté. Arrosez abondamment tout au long de l'été ; paillez généreusement ; fertilisez en mars. Cueillez-les frais pour les vases ou faites sécher les capitules pour des compositions hivernales.

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