Best NPK for Citrus Trees

Healthy citrus trees depend on balanced nutrition. The right NPK ratio shapes leaf colour, flower abundance, and fruit quality. Among modern blends, the CompleteGrow Advanced Formula NPK 4-18-38 + Calcium & Magnesium stands out for producing strong roots, rich foliage, and high-yield harvests with consistent flavour and colour.

Understanding the Right NPK Balance for Citrus

Citrus trees are heavy feeders that extract nutrients rapidly during flowering and fruiting. A fertiliser with a low nitrogen level and elevated phosphorus and potassium supports steady growth without overstimulating leaves. This makes the 4-18-38 ratio ideal for long-term fruit production and strong plant health.

Nitrogen (4%)

Supplies controlled green growth and maintains canopy colour. Too much nitrogen encourages soft, leafy shoots at the expense of flowers. The moderate 4 percent ensures balanced energy use and compact foliage.

Phosphorus (18%)

Drives root expansion and early flower formation. Citrus roots sit close to the surface; adequate phosphorus ensures nutrient uptake during rapid spring growth and heavy flowering.

Potassium (38%)

Essential for fruit density, sweetness, and rind quality. High potassium levels in the 4-18-38 blend increase juice content and help fruit withstand hot, dry conditions.

Added Calcium & Magnesium

Calcium strengthens cell walls and prevents rind splitting, while magnesium deepens green pigmentation and improves energy transfer within leaves. Together they keep citrus foliage glossy and resilient all year.

The result is a precise nutrient profile that supports flowering, maximises fruit size, and maintains vivid leaf colour—making NPK 4-18-38 + CaMg the most effective formula for long-term citrus vitality.

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How to Fertilise Citrus Trees for Lasting Growth and Fruit Quality

Timing is crucial when feeding citrus. Each growth phase demands different nutrient levels to build a strong root network, sustain flowering, and fill fruit to maturity. A structured routine using CompleteGrow Advanced NPK 4-18-38 + Calcium & Magnesium ensures balanced nutrition without the risk of over-feeding.

Seasonal Feeding Schedule

Spring (Sept – Nov): Apply a full feed as buds form to power new leaves and flowers. Dissolve 1–2 tablespoons per metre of canopy in water and drench the soil evenly.
Summer (Dec – Feb): Re-apply every 3–4 weeks to sustain fruit sizing and sweetness. Always water deeply after feeding to prevent salt concentration.
Autumn (Mar – Apr): Give a lighter feed to store energy for the next flowering cycle and strengthen roots before cooler weather.
Winter (May – Aug): Pause fertilising while growth slows. Focus on pruning and mulch renewal to protect soil moisture.

Feeding Citrus in Pots and Containers

Potted citrus trees dry out quickly and leach nutrients with frequent watering. Feed with a half-strength solution every 2–3 weeks during active growth, and flush pots with clean water monthly to prevent mineral build-up. The calcium and magnesium in the 4-18-38 formula stabilise foliage colour and maintain rind firmness even in limited soil volume.

Application Tips for Best Results

Water the soil before applying any fertiliser to protect fine feeder roots.
Spread evenly beneath the canopy, keeping fertiliser away from the trunk.
Feed early morning or late afternoon to minimise evaporation and leaf stress.
Mulch lightly after feeding to retain moisture and improve nutrient absorption.

Following this rhythm keeps nutrient availability steady year-round, resulting in consistent yields, fragrant blossoms, and a dense evergreen canopy that defines a well-fed citrus tree.

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Common Questions About Feeding Citrus Trees

Why choose a low-nitrogen fertiliser for citrus?

Excess nitrogen produces large, soft leaves but limits flower and fruit formation. A controlled 4 percent nitrogen level focuses plant energy on blossom production and balanced growth.

What does potassium do for citrus fruit?

Potassium enhances sugar formation, juice content, and peel strength. Trees fed with high-K blends like 4-18-38 consistently yield sweeter fruit with improved colour and shelf life.

My leaves are yellow between veins—what causes that?

This pattern indicates magnesium deficiency. The magnesium in the CompleteGrow Advanced Formula quickly restores chlorophyll balance and deepens leaf tone within a few weeks of consistent feeding.

How often should mature trees be fertilised?

Mature citrus respond best to lighter, more frequent applications—every 4–6 weeks through spring and summer—rather than large infrequent doses. Regular micro-feeding keeps nutrient uptake stable.

Final Recommendation

For vibrant foliage, heavy flowering, and full-flavoured fruit, feed citrus with

CompleteGrow Advanced NPK 4-18-38 + Calcium & Magnesium

Its precise balance of nutrients keeps trees productive and healthy season after season—delivering greener leaves, firmer rinds, and citrus harvests that truly stand out.