Lush, deep-green growth starts with magnesium. It sits at the heart of every chlorophyll molecule, the engine behind photosynthesis, so when plants have enough of it, they green up, grow vigorously, and put more energy into leaves, flowers, and fruit. Magnesium Sulphate, better known as Epsom salts, is one of the quickest ways to give them magnesium, along with a solid dose of plant-available sulphur in a single application.
It is a clear, fully water-soluble crystalline mineral supplying 9.8% magnesium (Mg) and 13% sulphur (S). Because it dissolves completely and both nutrients are ready for the plant to take up right away, it works fast, whether you water it into the root zone or spray it straight onto the leaves. It supplies magnesium without raising soil pH, so you can correct a deficiency without disturbing soil chemistry you already have dialled in.
From a single houseplant or raised bed up to market gardens, orchards, vineyards, and field crops, Magnesium Sulphate is a simple, proven way to keep plants healthy, productive, and green.
The role of magnesium and sulphur in plants
Magnesium and sulphur are both secondary nutrients, needed in smaller amounts than nitrogen, phosphorus, and potassium, but no less essential to how a plant functions.
Magnesium: Beyond its role in chlorophyll, magnesium activates a wide range of plant enzymes, drives the energy transfer that powers growth, and helps move sugars and other nutrients through the plant. Because it is mobile within the plant, a shortage appears first on the oldest leaves as the plant pulls magnesium toward new growth.
Sulphur: Sulphur is a building block of amino acids, proteins, and several plant enzymes and vitamins, so it underpins protein synthesis and works alongside nitrogen in overall development. At 13%, Magnesium Sulphate delivers a meaningful sulphur contribution in the same application as the magnesium.
Who it's for
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Home gardens and raised beds: quick correction of yellowing on tomatoes, peppers, potatoes, roses, and other magnesium-hungry crops.
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Containers and houseplants: soluble drench or foliar dosing to correct magnesium yellowing without overloading a small root zone.
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Greenhouse and market garden: foliar or fertigation dosing for a fast in-season response.
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Orchard and vineyard: foliar programs timed off tissue analysis, where magnesium demand runs high through fruit development.
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Broadacre and field crops: soluble magnesium and sulphur for foliar or fertigation use across larger acreages.
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Cannabis: magnesium is a common limiting nutrient in fast-growing, heavy-feeding crops, and Magnesium Sulphate is a simple way to top it up in soil or hydroponic feeds.
How to apply
Before dosing, confirm the deficiency with a soil or tissue test where you can. Magnesium yellowing looks like several other nutrient issues, so a test tells you magnesium is actually the limiting nutrient and stops you from correcting a problem that isn't there.
Magnesium Sulphate dissolves fully in water and can be delivered as a foliar spray, a soil drench, or a dry application worked into the bed. Start on the low side and adjust to crop response.
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Foliar feed (fastest response): Dissolve 5 g in 1 L of water and spray to cover the leaves. Foliar feeding puts magnesium where the symptoms appear and provides the quickest visible results.
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Soil drench: Dissolve 0.5 g per 1 L of water (about 50 ppm Mg) and water in.
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Garden beds: Dissolve 10 g per 1 L of water and apply at 1 L per square metre (about 10 sq ft) of bed. For severe deficiency, repeat monthly until corrected.
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Fruit trees and shrubs: Apply 20 g per square metre, spread evenly out to the drip line. Keep it at least 10 cm back from the base of the plant, and water in well, rinsing any granules off the foliage.
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Broadacre, orchard, and vineyard (foliar): Base the rate on tissue analysis. Rates generally fall between 3 and 5 lbs per acre dissolved in 75 to 100 L of water.
Guaranteed analysis
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Magnesium (Mg): 9.8%
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Sulphur (S): 13%
Form: clear, water-soluble crystalline solid (magnesium sulphate heptahydrate).
Storage and safety
Keep out of reach of children and pets. Avoid contact with eyes, and wash any solution off plant foliage and off your skin after handling.
Approved for use in organic production
Magnesium Sulphate (Epsom salts) is permitted for use in organic production under CAN/CGSB-32.310-2026 and CAN/CGSB-32.311-2026.
