Fertilising guide

How to fertilise Sweet orange (Citrus sinensis)— schedule & NPK

Also called Sweet orange, Common orange.

More about sweet orange

About Sweet orange

Citrus sinensis · also called Sweet orange, Common orange · edible

Sweet orange is a subtropical evergreen tree producing juicy, vitamin-C-rich fruit. It requires full sun, well-drained acidic soil, and warm temperatures year-round. In cool climates it excels as a container specimen moved indoors for winter. Dwarf grafted trees are well suited to large pots and conservatories.

Growth habit: Evergreen tree; upright to rounded canopy with somewhat pendulous fruiting branches

Watch for — Nutrient deficiency (yellowing leaves): Interveinal yellowing on young leaves indicates iron or manganese deficiency (often a pH problem); overall yellowing points to nitrogen shortfall. Apply a balanced citrus fertiliser with chelated trace elements and check soil pH is 5.5–6.5.

What fertiliser sweet orange actually wants — and why

Sweet orange 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 sweet orange: 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 sweet orange, 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 sweet orange:

Feed with a specialist citrus fertiliser (high nitrogen, with magnesium and trace elements) every 4–6 weeks from early spring to early autumn. Reduce to every 8 weeks in winter. Yellowing leaves often signal nitrogen or magnesium deficiency. 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 sweet orange 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 sweet orange

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

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

Signs you are over-feeding sweet orange

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for sweet orange:

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 sweet orange

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 sweet orange care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Flush sweet orange 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 sweet orange

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 sweet orange — frequently asked questions

What fertiliser does sweet orange 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. Sweet orange 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 sweet orange?

Feed with a specialist citrus fertiliser (high nitrogen, with magnesium and trace elements) every 4–6 weeks from early spring to early autumn. Reduce to every 8 weeks in winter. Yellowing leaves often signal nitrogen or magnesium deficiency. Feed with a specialist citrus fertiliser (high nitrogen, with magnesium and trace elements) every 4–6 weeks from early spring to early autumn. Reduce to every 8 weeks in winter. Yellowing leaves often signal nitrogen or magnesium deficiency. 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 sweet orange?