Fertilising guide

How to fertilise Bigleaf Hydrangea 'Nikko Blue' (Hydrangea macrophylla 'Nikko Blue')— schedule & NPK

Also called Nikko Blue Mophead.

More about bigleaf hydrangea 'nikko blue'

About Bigleaf Hydrangea 'Nikko Blue'

Hydrangea macrophylla 'Nikko Blue' · also called Nikko Blue Mophead · flowering

'Nikko Blue' is a classic mophead bigleaf hydrangea with large rounded flower heads that turn vivid blue in acidic soil or pink in alkaline soil. A vigorous deciduous shrub blooming in summer on old wood, it needs moist, rich soil and shelter, and rewards correct pruning with its signature voluptuous blue domes.

Growth habit: Rounded, multi-stemmed deciduous shrub with large coarse leaves; blooms on old wood (last year's stems), so flower buds form in late summer for the following year.

What fertiliser bigleaf hydrangea 'nikko blue' actually wants — and why

Bigleaf Hydrangea 'Nikko Blue' 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.

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 bigleaf hydrangea 'nikko blue': 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 bigleaf hydrangea 'nikko blue', 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 bigleaf hydrangea 'nikko blue':

Feed in spring and early summer with a balanced shrub fertiliser; for blue flowers use a low-phosphorus feed and aluminium sulphate to acidify, or garden lime to shift toward pink. 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 bigleaf hydrangea 'nikko blue' 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 bigleaf hydrangea 'nikko blue'

Follow the ericaceous product's own rate — these are formulated for the plant, so the dilution on the label is right for bigleaf hydrangea 'nikko blue'. The variable that actually matters is pH, not concentration.

Feeding always goes onto already-damp soil, never dry roots — water bigleaf hydrangea 'nikko blue' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the bigleaf hydrangea 'nikko blue' watering schedule.

Signs you are over-feeding bigleaf hydrangea 'nikko blue'

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for bigleaf hydrangea 'nikko blue':

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 bigleaf hydrangea 'nikko blue'

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 bigleaf hydrangea 'nikko blue' care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Flush bigleaf hydrangea 'nikko blue' 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 bigleaf hydrangea 'nikko blue'

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 bigleaf hydrangea 'nikko blue' — frequently asked questions

What fertiliser does bigleaf hydrangea 'nikko blue' 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. Bigleaf Hydrangea 'Nikko Blue' 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 bigleaf hydrangea 'nikko blue'?

Feed in spring and early summer with a balanced shrub fertiliser; for blue flowers use a low-phosphorus feed and aluminium sulphate to acidify, or garden lime to shift toward pink. Feed in spring and early summer with a balanced shrub fertiliser; for blue flowers use a low-phosphorus feed and aluminium sulphate to acidify, or garden lime to shift toward pink. 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 bigleaf hydrangea 'nikko blue'?

What does over-feeding bigleaf hydrangea 'nikko blue' 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 bigleaf hydrangea 'nikko blue' 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 bigleaf hydrangea 'nikko blue'?