Plants
Bigleaf Hydrangea
Hydrangea macrophylla · Hydrangeaceae
The bigleaf hydrangea is the classic hydrangea with the big, round mophead blooms — the epitome of the summer front garden and one of the best-selling flowering shrubs of all. From June to September it flowers in pink, blue, violet or white, the blue shades being a small miracle of soil chemistry: they only develop in acidic soil with available aluminium. Take two things to heart — plenty of water and the right pruning — and it will give you decades of pleasure.
- Light
- Semi-shade to light shade; morning sun yes, harsh midday sun no.
- Watering
- Generous and regular — the soil should never dry out completely; rainwater is ideal.
- Care level
- Medium
- Botanical
- Hydrangea macrophylla
The botanical name Hydrangea roughly means water vessel, and that is the heart of its care: the large, soft leaves transpire enormously, and on hot days the plant demonstratively lets everything droop. A semi-shaded spot without harsh midday sun and evenly moist, humus-rich, low-lime soil therefore matter more than any fertiliser.
Flower colour can be steered in pink and blue cultivars: in acidic soil (pH around 4.5 to 5) with aluminium they flower blue, in neutral to slightly limy soil pink. To keep blue, water with rainwater, plant in ericaceous compost and apply hydrangea blueing agent (potassium alum). White cultivars stay white — there is nothing to be dyed here.
For pruning, the most important hydrangea rule applies: bigleaf hydrangeas flower on last year's wood, and the buds for next summer already sit at the shoot tips in autumn. So in spring only remove the old flower heads down to the first strong pair of buds and cut out frost damage — a hard prune costs the entire bloom. The exception are remontant cultivars such as the „Endless Summer“ series, which also flower on new growth.
Late frosts are the second classic hydrangea disappointment: if the plant leafs out early and then freezes back, the flowering largely fails. In harsh spots, a sheltered position near the house wall helps, plus fleece on forecast frost nights in late winter. Container plants overwinter best somewhere cool and frost-free.
In floristry, hydrangea blooms are doubly valuable: fresh as lavish soloists, and in late summer, once the heads have turned papery, as long-lasting dried flowers. For the vase, remember that hydrangeas also drink through their petals — floppy heads can often be revived with an upside-down dip in cold water.
Is Bigleaf Hydrangea toxic to children and pets?
- Children
- Mildly irritating
- Cats
- Toxic
- Dogs
- Toxic
All parts of the hydrangea contain small amounts of cyanogenic glycosides (hydrangin) and are considered toxic to cats and dogs. For children it is mildly toxic — serious poisoning is rare, as large amounts would have to be eaten. Still, keep it away from pets that like to chew.
Typical symptoms: After ingestion: vomiting, diarrhoea, abdominal pain and lethargy; in pets also drooling. Seek veterinary advice when in doubt.
In an emergency:call the German poison control centre in Bonn on +49 228 19240 (24/7) — for pets, contact an emergency vet directly. This information does not replace medical or veterinary advice.
Overview: toxic & non-toxic plants for cats, dogs and children
Care
- 01Semi-shaded position without harsh midday sun, ideally humid and sheltered.
- 02Keep the soil evenly moist — hydrangeas are exceptionally thirsty.
- 03Water with rainwater; hard tap water turns blue cultivars pink.
- 04In spring remove only old flower heads and frost damage, never prune hard.
- 05Feed with hydrangea or ericaceous fertiliser in spring.
- 06In harsh spots protect the buds with fleece during late frosts.
Frequently asked
- How do I get blue bigleaf hydrangeas?
- Blue only develops in pink- or blue-disposed cultivars in acidic soil (pH 4.5–5) with available aluminium. In practice: plant in ericaceous compost, water exclusively with rainwater and apply hydrangea blueing agent (potassium alum) in spring. In limy soil the colour inevitably shifts to pink; white cultivars cannot be coloured at all.
- Why is my bigleaf hydrangea not flowering?
- In the vast majority of cases the flower buds were removed or destroyed: either by pruning too hard in autumn or spring, or by late frost on the fresh growth. Only cut off old flower heads, protect with fleece in harsh spots — or switch to remontant cultivars such as „Endless Summer“, which rebloom on new wood.
- Is bigleaf hydrangea toxic to cats and dogs?
- Yes, hydrangeas are considered toxic to cats and dogs — all parts contain small amounts of cyanogenic glycosides. Typical effects after chewing are vomiting, diarrhoea and lethargy; severe poisoning is rare. If your pet visibly eats the plant, contact your vet to be safe.
- Why is my hydrangea drooping?
- Almost always lack of water — on hot days the large leaves transpire more than the roots can supply. Water deeply in the evening and the plant is usually upright again by morning. If it droops despite wet soil, check for the opposite problem: waterlogging and root damage.
- Can I keep bigleaf hydrangeas in containers?
- Yes, very well — the container should measure at least 30 to 40 centimetres across and never dry out. In winter, insulate the pot or move the plant somewhere cool and frost-free, as roots and flower buds freeze much faster in a container than in the ground.