Magnesium deficiency in New Zealand soils is more common than many gardeners realise, particularly in regions with naturally acidic soil or where intensive farming has depleted mineral levels. If your fruit trees—especially lemon trees—are showing yellowing leaves while the veins remain green, magnesium deficiency is likely the culprit.
Why Magnesium Matters for Fruit Trees
Magnesium is a core component of chlorophyll, the pigment that gives leaves their green colour and enables photosynthesis. Without adequate magnesium, your trees struggle to produce energy, resulting in weakened growth and reduced fruit yield. This deficiency typically appears first on older leaves and progresses upward as the tree reallocates remaining magnesium to new growth.
Recognising Magnesium Deficiency in Lemon Trees
Yellow or orange leaves with green veins are the classic sign. You may also notice:
- Premature leaf drop
- Poor fruit set or smaller fruit
- Slow, stunted growth
- A general lack of vigour in the canopy
NZ soils, particularly in Auckland and Waikato regions, can be naturally low in magnesium due to leaching and intensive cropping. Citrus trees are especially heavy feeders and deplete soil reserves quickly.
Fixing Yellow Leaves: The Epsom Salt Solution
Epsom salt (magnesium sulphate) is one of the fastest and most cost-effective ways to correct magnesium deficiency. Unlike slow-release soil amendments, Epsom salt is readily available to plant roots and produces visible results within weeks.
How to apply Epsom salt to fruit trees:
- Soil application: Dissolve 1–2 tablespoons per mature tree in water and apply around the root zone. Repeat every 4–6 weeks during the growing season (September to March in NZ).
- Foliar spray: Mix 1 tablespoon Epsom salt per litre of water and spray directly onto leaves early morning or late evening. This provides faster results for severe deficiencies.
- Frequency: Apply every 2–3 weeks for foliar treatment until symptoms improve, then revert to soil application for maintenance.
Fruit Tree Fertiliser Requirements in New Zealand
Beyond magnesium, citrus and other fruit trees in NZ need balanced nutrition:
- Nitrogen (N): Supports leafy growth; apply in spring and early summer.
- Phosphorus (P): Encourages root development and flowering; essential for fruit set.
- Potassium (K): Improves fruit quality and disease resistance.
- Magnesium (Mg): Maintains leaf health and photosynthetic efficiency.
- Trace elements: Zinc, iron, and boron support overall tree health.
A slow-release citrus fertiliser applied in spring, combined with Epsom salt supplementation, creates a robust feeding programme tailored to NZ conditions.
Why The Epsom Salt Company
We supply premium-grade Epsom salt specifically suited for garden and agricultural use across Auckland and New Zealand. Our product is pure, fast-acting, and cost-effective—ideal for treating magnesium deficiency in your fruit trees without harsh chemicals or complicated application methods.
Whether you're correcting an existing deficiency or maintaining healthy, productive trees, Epsom salt is a proven, natural solution backed by decades of horticultural practice in NZ gardens.