Fertilising guide
How to fertilise Hydrangea (Hydrangea macrophylla)— schedule & NPK
Also called mophead hydrangea, lacecap hydrangea, bigleaf hydrangea.
About Hydrangea
Hydrangea macrophylla · also called mophead hydrangea, lacecap hydrangea · flowering
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. Toxic to pets.
Bigleaf hydrangea (Hydrangea macrophylla) is native to China and Japan; it is the species famous for soil-driven flower-color change in blue/pink cultivars.
Feed in spring; note that fertilizers and soil amendments shift pH and aluminium availability, so feeding choices can alter bloom color in blue/pink types.
Growth habit: Deciduous flowering shrub
Sources: rhs.org.uk, missouribotanicalgarden.org, rhs.org.uk
What fertiliser hydrangea actually wants — and why
Hydrangea is an acid-loving plant — it can only take up nutrients in acidic soil, so the feed itself matters less than using an ericaceous formula and never liming.
An ericaceous (acidic) fertiliser, formulated to keep the soil pH low and supply iron and trace elements in a form acid-loving roots can absorb. Ordinary feeds and any lime lock out iron and yellow the leaves.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for hydrangea: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed hydrangea, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For hydrangea:
A balanced feed in early spring; an ericaceous feed and aluminium sulphate maintain blue colour on bigleafs. In practice: an ericaceous feed in spring as growth resumes, repeated through the main growing months; never apply lime, bonemeal or wood ash, which raise pH.
The dormant-season rule matters more than the exact interval: skip feeding entirely when hydrangea is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for hydrangea
Follow the ericaceous product's own rate — these are formulated for the plant, so the dilution on the label is right for hydrangea. The variable that actually matters is pH, not concentration.
Feeding always goes onto already-damp soil, never dry roots — water hydrangea first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the hydrangea watering schedule.
Signs you are over-feeding hydrangea
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for hydrangea:
- Brown, scorched leaf margins from too strong or too frequent a dose.
- White salt crust on the soil surface.
- Soft, lush growth that fruits or flowers poorly.
Signs you are under-feeding hydrangea
- Yellowing leaves with green veins (iron chlorosis from high pH).
- Weak growth, poor cropping and an overall pale, stressed look.
- Stunted new shoots in spring despite adequate water and light.
If the symptoms point at watering, light or roots rather than nutrition, the full hydrangea care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush hydrangea with rainwater (not hard tap water, which raises pH) if salts build up; better still, mulch with pine needles or composted bark and water with rainwater to hold the acidity.
Organic vs synthetic feeds for hydrangea
Organic options
Composted pine bark, pine-needle mulch, used coffee grounds and an organic ericaceous feed gently maintain acidity. UK: Vitax or Westland Ericaceous; US: Espoma Holly-tone or Dr. Earth Acid Lovers. Slow, soil-improving, hard to overdo.
Synthetic / liquid feeds
A liquid or granular ericaceous feed — UK: Miracle-Gro Ericaceous, Vitax or Westland; US: Miracle-Gro Acid-Loving Plant Food or Espoma Holly-tone. Pair with rainwater and an acidic mulch for it to work.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising hydrangea — frequently asked questions
What fertiliser does hydrangea need?
An ericaceous (acidic) fertiliser, formulated to keep the soil pH low and supply iron and trace elements in a form acid-loving roots can absorb. Ordinary feeds and any lime lock out iron and yellow the leaves. Hydrangea is an acid-loving plant — it can only take up nutrients in acidic soil, so the feed itself matters less than using an ericaceous formula and never liming.
How often should I feed hydrangea?
A balanced feed in early spring; an ericaceous feed and aluminium sulphate maintain blue colour on bigleafs. A balanced feed in early spring; an ericaceous feed and aluminium sulphate maintain blue colour on bigleafs. In practice: an ericaceous feed in spring as growth resumes, repeated through the main growing months; never apply lime, bonemeal or wood ash, which raise pH.
What strength of feed for hydrangea?
Follow the ericaceous product's own rate — these are formulated for the plant, so the dilution on the label is right for hydrangea. The variable that actually matters is pH, not concentration.
What does over-feeding hydrangea look like?
Brown, scorched leaf margins from too strong or too frequent a dose. White salt crust on the soil surface. Soft, lush growth that fruits or flowers poorly. Feeding hydrangea an ordinary fertiliser, or growing it in hard tap water / limey soil, is the defining mistake — it triggers lime-induced chlorosis (yellow leaves, green veins) no amount of feeding fixes until the pH comes down.
Should I flush the soil of hydrangea?
Flush hydrangea with rainwater (not hard tap water, which raises pH) if salts build up; better still, mulch with pine needles or composted bark and water with rainwater to hold the acidity.
Keep reading
- Hydrangea care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water hydrangea — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise peace lily
- How to fertilise bird of paradise
- How to fertilise hoya
- All 200 fertilising guides in the Growli library