If your citrus trees are showing yellowing leaves, you're not alone—this is a common problem in New Zealand gardens, and magnesium deficiency is often the culprit. The good news is that epsom salt (magnesium sulfate) is an affordable, effective remedy that can help restore your trees' health and vibrant green foliage.
Why Citrus Trees Turn Yellow
Yellowing leaves on citrus trees typically signal magnesium deficiency. Magnesium is essential for chlorophyll production, the pigment that gives plants their green colour. When your soil lacks this vital nutrient, new growth appears pale or yellow, even though the leaf veins may remain green. This condition is particularly common in acidic or sandy soils across Auckland and the wider Auckland region.
How Epsom Salt Helps
Epsom salt is magnesium sulfate—a naturally occurring compound that delivers readily available magnesium directly to your plants. Unlike synthetic fertilisers, it's gentle, cost-effective, and works quickly. Most gardeners see improvement in leaf colour within 2–4 weeks of treatment.
How to Apply Epsom Salt to Your Citrus Trees
Soil Application (Best for established trees):
- Dissolve 1 tablespoon (approximately 15g) of epsom salt per litre of water.
- Water the soil around the base of your tree, avoiding direct contact with the trunk.
- Apply once per month during the growing season (spring and summer).
- For larger trees, scale up: use 2–3 tablespoons per 10 litres of water.
Foliar Spray (Fastest results):
- Mix 1 tablespoon of epsom salt per litre of water in a spray bottle.
- Spray the undersides of leaves early morning or late evening to avoid leaf burn.
- Repeat every 2–3 weeks during the growing season.
- This method delivers magnesium directly through the leaf surface.
Dry Application:
- Sprinkle 1–2 tablespoons of epsom salt around the drip line of your tree (where water naturally falls from branches).
- Water thoroughly after application to dissolve the salt into the soil.
- Apply once per month.
Finding Epsom Salt in New Zealand
Epsom salt is widely available and affordable across New Zealand. You'll find it at most hardware stores, garden centres, and supermarkets in the health and wellness section (it's also used for bath soaks). Check local retailers in Auckland or online for competitive pricing. Prices typically range from very affordable for small bags to economical bulk options.
Additional Tips for Healthier Citrus
While epsom salt addresses magnesium deficiency, maintaining overall plant health requires attention to other factors. Ensure your citrus trees receive full sun (at least 6–8 hours daily), well-draining soil, and regular watering during dry spells. A balanced citrus-specific fertiliser applied in spring and summer will provide additional nutrients. Mulch around the base to retain moisture and regulate soil temperature.
If yellowing persists after two months of epsom salt treatment, consider a soil test to rule out other deficiencies or pH imbalances. Your local garden centre or regional council can often provide guidance on soil testing services in Auckland.
With consistent care and regular epsom salt applications, your citrus trees should recover their vibrant green foliage and reward you with healthy, productive growth.