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Potassium for Citrus Trees: Why It Matters for Flowering, Fruit Size and Quality

Potassium is one of the most important nutrients for citrus trees. It directly influences flowering, fruit set, fruit size, sweetness, peel strength, and overall stress tolerance. Citrus trees with adequate potassium produce better crops, stronger fruit, and more consistent yields.

While nitrogen drives leafy growth, potassium is the nutrient that turns flowers into fruit. Many citrus trees grow well but fruit poorly because potassium supply is too low or poorly balanced.

Recommended fertiliser for citrus potassium needs

Use a potassium-rich citrus fertiliser such as Citrus Fertiliser – Lemon, Lime & Orange Tree (NPK 6-2-12 + Trace Elements).
The 12% potassium (K) is intentionally higher than nitrogen to support flowering, fruit set and fruit development.
Moderate nitrogen prevents excessive leafy growth that can reduce flowering.
Added trace elements support nutrient uptake and prevent secondary deficiencies.

What potassium does inside citrus trees

Supports flower formation and fruit set
Improves fruit size, firmness and juice quality
Regulates water movement and stress tolerance
Strengthens cell walls and fruit peel
Improves resistance to heat and drought stress

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Citrus Potassium Deficiency: Symptoms and Common Causes

Potassium deficiency in citrus trees often shows during flowering and fruiting stages. Trees may look healthy early in the season but struggle to hold fruit, produce small fruit, or drop fruit prematurely.

Potassium deficiency symptoms in citrus

Poor flowering or flowers dropping early
Small, thin-skinned or misshapen fruit
Fruit drop during development
Leaf edge yellowing or scorching on older leaves
Reduced drought tolerance and stress resistance

Why citrus trees become potassium deficient

Overuse of nitrogen-heavy fertilisers
Leaching in sandy soils or pots
High crop load draining potassium reserves
Infrequent feeding during fruit development

Potassium deficiency is often mistaken for general stress or blamed on pests. In reality, fruiting citrus trees have much higher potassium demand than leafy growth demand. Balanced feeding is essential once flowering begins.

Low potassium

Poor flowering, fruit drop, small or weak fruit.

Too much nitrogen

Strong leaf growth but poor fruiting and delayed maturity.

Balanced potassium

Consistent flowering, better fruit set and improved fruit quality.

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How to Use Potassium Correctly for Citrus Trees

Potassium should increase as citrus trees move from vegetative growth into flowering and fruiting. This does not mean eliminating nitrogen, but rather ensuring potassium remains dominant during fruit development.

Best practice potassium feeding strategy

Use a potassium-rich citrus fertiliser consistently during spring and summer
Avoid switching to high-nitrogen products once flowering starts
Feed regularly rather than heavily to avoid leaching losses
Ensure trace elements are present to support uptake

Why citrus-specific fertilisers work better

Citrus fertilisers with higher potassium, such as NPK 6-2-12, align with the natural nutrient demand of fruiting citrus trees. They support both canopy health and fruit performance without pushing excessive leaf growth.

FAQ: Potassium for Citrus Trees

Is potassium good for citrus trees?
Yes. Potassium is essential for flowering, fruit set, fruit size and overall fruit quality.

What does potassium deficiency look like in citrus?
Poor flowering, fruit drop, small or weak fruit, and yellowing or scorching on older leaf edges.

Can too much nitrogen cause potassium problems?
Yes. Excess nitrogen increases potassium demand and can worsen deficiency if potassium is not increased accordingly.

What fertiliser is best for potassium in citrus trees?
A citrus-specific fertiliser with higher potassium than nitrogen, such as an NPK 6-2-12 formulation, is ideal.

Does potassium affect citrus fruit taste?
Yes. Adequate potassium improves fruit firmness, juice content, sweetness and overall eating quality.