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

Magnesium Sulphate (Epsom Salt): Magnesium & Sulphur for Plants and Gardens

Magnesium Sulphate Heptahydrate, better known as Epsom Salt, is a fully water-soluble crystalline compound that supplies two important plant nutrients: magnesium and sulphur. It's a versatile, economical product used across agriculture, horticulture, gardens and industry, and it's especially valued for correcting magnesium deficiency in plants. It's available in 1kg, 2kg, 4kg and 25kg, so you can buy a small tub for pots or a bulk bag for the orchard.

Why Plants Need Magnesium

Magnesium sits at the centre of the chlorophyll molecule, so it's 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 stay green, often in tomatoes, citrus, roses, palms and potted plants. Because Epsom Salt dissolves completely, it delivers magnesium quickly 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's worth doing a soil or tissue test first and not over-applying, as 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.

Specifications

• Chemical formula: MgSO₄·7H₂O
• Appearance: white crystalline granules
• Solubility: fully soluble in water
• Supplies: magnesium and sulphur
• Sizes: 1kg, 2kg, 4kg and 25kg

Key Features & Benefits

• Fully water-soluble source of magnesium and 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

Frequently Asked Questions

What is magnesium sulphate used for on plants?
It's 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's 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; "sulfate" is the US spelling, but it's 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 aren't magnesium deficient, adding more won't 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 doesn't significantly acidify soil, unlike some other treatments. It simply supplies magnesium and sulphur.

What Weights does it come in?
It's available in 1kg, 2kg, 4kg and 25kg, with the 25kg bag suited to larger gardens, orchards and commercial use.

Where can I buy Epsom Salt in Australia?
It's available online from BPG Supplies, with free in-store pick-up from our Bonnyrigg location in South-West Sydney.