Redox Magnesium Sulphate Heptahydrate (Epsom Salt) – Magnesium & Sulphur for Plants

Magnesium and Sulphur for Plants and Gardens

Magnesium Sulphate Heptahydrate, better known as Epsom Salt, is a fully water-soluble compound that supplies two important plant nutrients: magnesium and sulphur. This is the Redox product, analysing at around 9.7% magnesium and 12.9% sulphur, a versatile and economical input used across agriculture, horticulture and the garden, and especially valued for correcting magnesium deficiency in plants. It is available in 1kg, 2kg, 4kg and 25kg, so you can grab a small pack for pots and beds or a bulk bag for the orchard.

Why Plants Need Magnesium

Magnesium sits at the centre of the chlorophyll molecule, so it is essential for photosynthesis and healthy green foliage, while sulphur supports protein and enzyme function. When plants run short of magnesium, they show interveinal chlorosis, a distinctive yellowing between the leaf veins while the veins themselves stay green, often seen in tomatoes, citrus, roses, palms and potted plants. Because Epsom Salt dissolves completely, it delivers magnesium quickly, either through the soil or as a foliar spray.

How to Use in the Garden

Epsom Salt is best used to correct a known or suspected magnesium deficiency rather than as a routine feed, so it is worth doing a soil or tissue test first and not over-applying, since excess can build up salts and unbalance other nutrients. As a general guide:

• Foliar spray: dissolve around 5 to 20g per litre of water and spray thoroughly over the leaves, in the morning or late afternoon to avoid leaf burn. This gives the fastest correction of deficiency.
• Soil and garden beds: dissolve about 10g per litre and apply at roughly 1 litre per square metre.
• Fruit trees and shrubs: apply around 20g per square metre, spread evenly out to the drip line, keeping it about 10cm away from the trunk or base.
• Frequency: monthly for severe deficiency, otherwise as needed based on testing.

Key Features & Benefits

• Fully water-soluble source of magnesium and sulphur
• Redox analysis: approx. 9.7% magnesium, 12.9% sulphur
• Corrects magnesium deficiency and interveinal yellowing in plants
• Supports chlorophyll production and healthy green foliage
• Works as a fast-acting foliar spray or soil application
• Useful on tomatoes, citrus, roses, palms and potted plants
• Available in 1kg, 2kg, 4kg and 25kg, shipped Australia-wide

Product Details

• Product: Magnesium Sulphate Heptahydrate (Epsom Salt)
• Grade: Horticultural / technical, for garden and agricultural use
• Chemical formula: MgSO₄·7H₂O
• Analysis: Approx. Mg 9.7%, S 12.9%
• Appearance: White crystalline product
• Solubility: Fully soluble in water
• Available sizes: 1kg, 2kg, 4kg, 25kg
• Brand: Redox

Frequently Asked Questions

What is magnesium sulphate used for on plants?
It is used to correct magnesium deficiency, which shows as yellowing between the leaf veins. Magnesium supports chlorophyll and green growth, and sulphur supports overall plant health. It is commonly used on tomatoes, citrus, roses and palms.

How much Epsom salt do I use per litre of water?
For a foliar spray, dissolve around 5 to 20g per litre and spray the leaves. For soil application, about 10g per litre applied at 1 litre per square metre. Always start with a soil test and avoid over-applying.

Is Epsom salt the same as magnesium sulphate?
Yes. Epsom salt is the common name for magnesium sulphate (specifically the heptahydrate form). "Sulphate" is the Australian and UK spelling, while "sulfate" is the US spelling, but it is the same compound.

When should I use Epsom salt in the garden?
Use it to treat a known or suspected magnesium deficiency, not as a routine fertiliser. If your plants are not magnesium deficient, adding more will not improve growth and can unbalance the soil, so test first.

Will Epsom salt make my soil acidic or change pH?
Magnesium sulphate is close to pH neutral and does not significantly acidify soil, unlike some other treatments. It simply supplies magnesium and sulphur.

What weights does it come in?
It is available in 1kg, 2kg, 4kg and 25kg, with the 25kg bag suited to larger gardens, orchards and agricultural use.

Where can I buy Epsom Salt in Australia?
It is available online from BPG Supplies, with shipping across Australia and local pickup in Bonnyrigg, South-West Sydney.