Epsom Salt & Magnesium for Yellow Leaves

Epsom salt is magnesium sulphate (MgSO4), a soluble source of magnesium and sulphur. Magnesium sits at the centre of the chlorophyll molecule, so it is essential for photosynthesis; supplying it corrects deficiency, greens up pale leaves and supports vigorous growth and fruiting.

The classic sign is interveinal chlorosis on older leaves — the leaf veins stay green while the tissue between them turns yellow, because the plant moves mobile magnesium up to younger growth. It shows first on lower, older leaves, often on sandy, acidic or high-potassium soils. A leaf or soil test confirms it.

Magnesium sulphate heptahydrate, the usual Epsom salt, is about 9.8% magnesium and around 13% sulphur. So to supply a given amount of magnesium you need roughly ten times that mass of Epsom salt. The calculator handles this conversion both ways for you.

Use a low-concentration foliar spray for a quick fix when symptoms appear, because leaves absorb magnesium directly within days. Use a soil application per hectare for a lasting correction that feeds the crop through its roots over the season. Many growers do a foliar rescue first, then address the soil.

Epsom salt foliar sprays are usually mixed at a low concentration — commonly around 1–2% solution, or roughly 10–20 grams per litre of water — to avoid leaf scorch. Spray in cool conditions, cover the foliage to run-off, and repeat every couple of weeks if needed rather than over-concentrating.

Choose foliar or soil mode and enter your target — a spray volume and concentration, or an area and per-hectare rate. The tool returns the Epsom salt to apply and the magnesium that supplies, using the 9.8% magnesium content of magnesium sulphate. Mode is shown so you can plan the right kind of application.

Yes. Excess magnesium can unbalance soil cations and compete with calcium and potassium uptake, and strong foliar sprays scorch leaves. Only apply it where a deficiency is real — confirmed by symptoms or a test — rather than as a routine tonic, and keep foliar concentrations low.

No. Dolomitic lime supplies magnesium while raising pH on acid soils, kieserite is a slower-release magnesium sulphate, and compound fertilisers can include magnesium. Epsom salt is favoured for its high solubility, making it ideal for foliar sprays and fertigation where a fast, water-soluble source is needed.

Magnesium deficiency causes interveinal yellowing, not blossom-end rot — that is a calcium problem, and adding magnesium can even worsen it by competing with calcium. Diagnose the actual deficiency before reaching for Epsom salt; it is a magnesium and sulphur supplement, not a cure-all.

They are accurate for the 9.8% magnesium content of standard Epsom salt, but real plant response depends on soil magnesium, pH, competing nutrients and how thoroughly foliage is wetted. Treat the dose as a starting point, verify deficiency with a test, and adjust based on the crop's recovery.