Mandarin Tree Leaves Turning Yellow: What It Usually Means

Why Mandarin Tree Leaves Turn Yellow

Watering imbalance and root stress

Overwatering is one of the most common causes of yellow leaves on mandarin trees. When soil stays wet for too long, roots lose oxygen and cannot absorb nutrients efficiently, even if fertiliser is present. This leads to yellowing, leaf drop, and weak growth.

Underwatering can cause similar symptoms. Dry soil limits nutrient movement to the roots, reducing chlorophyll production and causing leaves to yellow, particularly during hot weather.

• Water deeply, then allow the soil surface to partially dry.
• Ensure pots drain freely and never sit in water.
• In-ground trees benefit from deep, infrequent watering rather than shallow daily irrigation.

Nutrient imbalance and poor fertiliser choice

Mandarin trees require a specific nutrient balance to stay green and productive. General-purpose fertilisers are often too high in nitrogen or lack sufficient potassium, which can destabilise growth and reduce nutrient efficiency.

Using a citrus fertiliser designed specifically for citrus plants helps maintain stable leaf colour by supplying nutrients in ratios mandarins can consistently use. A fruiting-friendly balance such as NPK 6-2-12 supports leaf health while prioritising flowering and fruit quality.

Magnesium and calcium demand during fruiting

Yellowing often appears during flowering and fruit development, when calcium and magnesium demand increases. Magnesium is essential for chlorophyll production, while calcium supports strong leaf and fruit structure.

If yellowing persists despite correct watering and feeding, supplementing with a Cal-Mag fertiliser during high-demand periods can help restore leaf colour and stabilise growth, particularly in pots or sandy soils.