Moderate Flowering Toxic to pets

Hydrangea

Hydrangea macrophylla

Hydrangea is a majestic deciduous shrub whose enormous colorful ball-shaped inflorescences brighten shaded gardens throughout summer.

The essentials at a glance

Watering

Every 2 days
Light

Bright indirect light
Humidity

60–80 %
Temperature

-10–25 °C

How to care for your Hydrangea

Everything you need to keep your Hydrangea healthy: watering, light, humidity, feeding, repotting and pruning.

Hydrangea macrophylla originates from Japan and was introduced to Europe in the 18th century. Its imposing globular inflorescences can measure up to 25 cm in diameter and display a palette ranging from white to deep blue, through pink and purple. Its fascinating peculiarity is the ability to change color depending on soil pH. It is a shrub that excels in shade and cool soil, ideal for woodland gardens and north-facing facades.

Watering your Hydrangea

Every 2 days

Water copiously and regularly, especially in summer. Hydrangea is extremely thirsty. Apply a mulch at the base to retain moisture.

How to know it needs water

Leaves and flowers wilted and drooping
Soil dry at the surface
Leaf margins browning

How much light a Hydrangea needs

Bright indirect light

Partial shade to dappled light. Direct morning sun is acceptable but avoid the scorching afternoon sun which singes the flowers.

Direct sun tolerated: 2 to 4 h a day
Orientations that suit it: North, North-east, East, South-east, South, South-west, West, North-west

Humidity and misting

60–80 %

60–80% No misting necessary outdoors. If temporarily kept in a pot indoors, maintain good ambient humidity.

Feeding and fertiliser

Every 30 days

Fertilize in spring at bud break. Soil pH determines colour: acidic soil = blue flowers, alkaline soil = pink flowers. Add crushed slate or aluminium sulphate to increase blueness.

Recommended feed: Acidic-soil plant fertilizer in spring. Aluminium sulphate to obtain blue flowers on alkaline soil. · 10-5-10

Repotting your Hydrangea

Every 24 months

Ericaceous compost blended with standard compost. An acidic soil (pH 4.5–5.5) is essential. In the ground, amend with ericaceous compost and acid compost.

When: Autumn or early spring
Potting mix: Ericaceous compost
Mix in: pine bark, coco fibre

The tell-tale signs

Roots emerging from drainage holes
Plant drying out very quickly
Reduced flowering

Pruning your Hydrangea

In late winter (February–March), before buds break. Cut dried flower heads back to the first pair of well-formed buds. Remove dead wood and the oldest stems at the base to renew the shrub (one third of stems each year).

Through the year

Watering is not set once and for all: it follows the light and the growth. Allow 4 days between waterings in the depth of winter, against 1 in the growing season.

Active growth · Days between waterings

Toxicity

All parts are toxic to animals and humans. Contains cyanogenic glycosides that can cause nausea, vomiting, and diarrhoea.

Good to know

Hydrangea can change its flower color depending on soil acidity: it turns blue in acidic soil and pink in alkaline soil due to aluminium absorption.
Its Latin name Hydrangea means 'water vessel' in Greek, referring to the shape of its seed capsules and its legendary thirst.

Frequently asked questions about the Hydrangea

How do you care for a Hydrangea?

Water it every 2 days. Give it bright indirect light. Ideal humidity: 60–80 %. Ideal temperature: -10–25 °C. Water copiously and regularly, especially in summer. Hydrangea is extremely thirsty. Apply a mulch at the base to retain moisture.

How often should you water a Hydrangea?

Every 2 days Water copiously and regularly, especially in summer. Hydrangea is extremely thirsty. Apply a mulch at the base to retain moisture. How to know it needs water : Leaves and flowers wilted and drooping ; Soil dry at the surface ; Leaf margins browning.

How much light does a Hydrangea need?

Bright indirect light Partial shade to dappled light. Direct morning sun is acceptable but avoid the scorching afternoon sun which singes the flowers. 2 to 4 h a day

Is the Hydrangea toxic to cats and dogs?

Yes. All parts are toxic to animals and humans. Contains cyanogenic glycosides that can cause nausea, vomiting, and diarrhoea. Keep it out of reach of your pets and call a vet if any is swallowed.

Why are my Hydrangea leaves turning yellow?

Yellowing most often comes from too much water: the mix stays wet and the roots suffocate. Check that the pot drains, empty the saucer, and let the mix dry before watering again. Too little light or a cold draught cause the same symptom.

When should you repot a Hydrangea?

Repot every 24 months, ideally in autumn or early spring. Ericaceous compost blended with standard compost. An acidic soil (pH 4.5–5.5) is essential. In the ground, amend with ericaceous compost and acid compost.