Wicked Organics Organic Organic OMRI Listed

Magnesium Sulfate

NPK N/A

Magnesium sulfate — commonly known as Epsom salt — is a fast-acting, water-soluble source of two essential secondary nutrients: magnesium (10%) and sulfur (13%). While it carries an NPK of 0-0-0, its role in plant health is critical. Magnesium is the central atom in chlorophyll, the molecule that drives photosynthesis, and sulfur is essential for protein synthesis and enzyme function.

When plants are deficient in magnesium, leaves yellow between the veins (interveinal chlorosis), starting with older foliage. Sulfur deficiency shows as uniform yellowing of new growth. Magnesium sulfate corrects both deficiencies rapidly because it dissolves completely in water and is immediately available to plant roots or through foliar absorption.

Old Cobblers Farm™ Wicked Organics Magnesium Sulfate is food-grade quality and approved for organic production. Use it as a soil drench, foliar spray, or dry broadcast to keep your plants green, productive, and photosynthesizing at peak efficiency.

Application Rates FAQs
Nutrient Profile
WO-EPSOM-SALT
N/A
Magnesium Sulfate
Derived From
  • Naturally mined magnesium sulfate heptahydrate (MgSO4·7H2O), commonly known as Epsom salt
N/A
NPK Ratio
Organic
Formula Type
Every 4-6 weeks during the growing season
Feeding Frequency
—
Compatible Plants
What It Is

Understanding 0-0-0

Magnesium sulfate is a naturally occurring mineral compound with the chemical formula MgSO4. In its hydrated form (Epsom salt), it contains approximately 10% magnesium and 13% sulfur by weight. It is one of the most water-soluble magnesium sources available, which makes it ideal for both soil application and foliar feeding.

Magnesium plays a central role in photosynthesis as the core element of the chlorophyll molecule. Without adequate magnesium, plants cannot efficiently convert sunlight into energy, leading to reduced growth and pale foliage. Sulfur supports amino acid and protein production, influences flavor in crops like onions and garlic, and helps plants access other nutrients.

Unlike many fertilizers, magnesium sulfate does not significantly alter soil pH, making it safe to use across a wide range of soil types. It is especially beneficial on sandy or acidic soils where magnesium leaches easily.

N
Nitrogen — 0%

N/A — Magnesium sulfate contains no nitrogen.

P
Phosphorus — 0%

N/A — Magnesium sulfate contains no phosphorus.

K
Potassium — 0%

N/A — Magnesium sulfate contains no potassium. However, it provides approximately 10% magnesium and 13% sulfur — two essential secondary nutrients.

Recommended Plants

Best For

Tomatoes
Peppers
Roses
Potatoes
Blueberries
Evergreens
Lawns
Herbs

Growing Detail

Tomatoes and peppers are heavy magnesium users and commonly develop deficiency symptoms mid-season — Epsom salt applied as a foliar spray or side-dress corrects this quickly. Roses respond with deeper green foliage and more prolific blooms. Potatoes benefit from the sulfur component, which improves tuber quality. Blueberries and evergreens growing in acidic, sandy soils are prone to magnesium leaching and benefit from regular supplementation.
Dosing Guide

Application Rates

Garden Beds
1-2 lbs per 100 sq ft
Container / Pot
1 tbsp per gallon of soil or dissolved in water
Water Mix
1-2 tbsp per gallon of water for foliar spray or soil drench
Lawn
3-5 lbs per 1,000 sq ft
Trees
2 tbsp per gallon of water, drench root zone
Per Acre
100-200 lbs per acre
Frequency
Every 2-4 weeks

How to Apply

Seasonal Notes

Apply magnesium sulfate from early spring through late summer during active growth. Foliar sprays are most effective during rapid vegetative growth and early fruiting. Avoid late fall application as plants enter dormancy. For evergreens, an early spring application helps prevent winter damage.
How It Compares

Side by Side

Magnesium sulfate vs. Dolomitic Lime: Both supply magnesium, but dolomitic lime also raises soil pH significantly. Use Epsom salt when you need magnesium without altering pH. Magnesium sulfate vs. Sul-Po-Mag: Sul-Po-Mag (0-0-22) provides potassium, magnesium, and sulfur — use it when potassium is also needed. Use Epsom salt for targeted magnesium/sulfur supplementation.

Safety & Storage

Magnesium sulfate is non-toxic and food-grade safe. No special protective equipment is required, though gloves are recommended for extended handling. Store in a dry location — Epsom salt absorbs moisture readily and can clump if exposed to humidity. Keep in a sealed container.

Got Questions?

Frequently Asked

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