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Plant care

Hydrangea care

Hydrangea macrophylla

Also called mophead hydrangea, lacecap hydrangea, bigleaf hydrangea.

RHS H5USDA 5-9 for H. macrophyllaToxic to petsIndoor 1-2 m tall and wide for most bigleafs

Watering rhythm

Bright indirect light (just back from a sunny window)

Deep watering 1-2 times per week, more in heat

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Light

Bright indirect light (just back from a sunny window)

Soil

Rich, moisture-retentive loam

Humidity

40-70% (outdoor)

Temp

13-24°C

Pet safety

Toxic to pets

Mature size

1-2 m tall and wide for most bigleafs

Care at a glance

Light

Hydrangea is what florists mean by "bright spot, no direct sun" — close enough to a south or east window to feel the brightness, with a sheer curtain or a few feet of distance keeping the sun off the leaves. Morning sun with afternoon shade in warm climates; near-full sun in cool climates. Deep shade reduces flowering. A phone lux-meter at the leaf surface should read 1,500-3,000 lux at noon.

Watering

Water hydrangea deep watering 1-2 times per week, more in heat. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Shallow-rooted and quick to wilt; mulch heavily and water deeply rather than little-and-often.

Soil and pot

Hydrangea grows best in rich, moisture-retentive loam. Compost-rich. pH 5.0-5.5 for blue flowers, 6.5+ for pink. Aluminium availability drives the colour shift. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Hydrangea sits happiest at around 40-70% (outdoor) humidity and 13-24°C (55-75°F). Outdoor humidity rarely matters. If you keep the room above 13 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed hydrangea sparingly. A balanced feed in early spring; an ericaceous feed and aluminium sulphate maintain blue colour on bigleafs. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on hydrangea in the Growli community. Each is annotated with the most common cause so you know where to start.

  • No flowers — Pruned at the wrong time — bigleafs flower on old wood, panicle types flower on new wood.
  • Wilting in summer — Shallow roots in hot sun; mulch heavily and move plant if possible.
  • Brown crispy flower heads — Sun scorch on cut flowers indoors, or natural end-of-season ageing.
  • Powdery mildew — Common in late summer; improve airflow.
  • Aphids — Common on new growth; rinse off with water.

Companion plants

Hydrangea pairs well with Hosta, Astilbe, and Fern. These are species with similar light and water needs, so you can group them in the same room or on the same shelf and water as a batch.

Propagation

Softwood cuttings in early summer under a humidity dome root in 4-6 weeks. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Hydrangea is toxic to pets. ASPCA lists Hydrangea as toxic to cats, dogs, and horses due to cyanogenic glycosides. Symptoms include vomiting, diarrhoea, and lethargy. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Hydrangea care — frequently asked questions

What is Hydrangea?

Hydrangea (Hydrangea macrophylla) is a flowering plant with a deciduous flowering shrub growth habit, reaching 1-2 m tall and wide for most bigleafs at maturity. Hydrangea is a deciduous shrub with large rounded (mophead) or flat (lacecap) flower heads from midsummer to autumn. Flower colour on bigleaf types depends on soil pH — acidic gives blue, alkaline gives pink.

How much light does hydrangea need?

Hydrangea grows best in bright indirect light (just back from a sunny window). Morning sun with afternoon shade in warm climates; near-full sun in cool climates. Deep shade reduces flowering.

How often should I water hydrangea?

Water hydrangea deep watering 1-2 times per week, more in heat. Shallow-rooted and quick to wilt; mulch heavily and water deeply rather than little-and-often. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is hydrangea toxic to cats and dogs?

Hydrangea is toxic to pets. ASPCA lists Hydrangea as toxic to cats, dogs, and horses due to cyanogenic glycosides. Symptoms include vomiting, diarrhoea, and lethargy.

What USDA hardiness zone does hydrangea grow in?

Hydrangea is rated for USDA zone 5-9 for H. macrophylla; 3-9 for paniculata; 3-8 for arborescens and RHS hardiness H5. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Hydrangea deep-dive guides

Every aspect of hydrangea care, each with its own calibrated guide:

Featured in these plant shortlists

Hydrangea qualifies for 3 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Hydrangea is also known as mophead hydrangea, lacecap hydrangea, and bigleaf hydrangea.