How much Epsom salt to use for your plants

The idea

Use Epsom salt to supplement magnesium and sulfur for both indoor and outdoor plants.

For indoor potted plants, dissolve 1 teaspoon of Epsom salt per gallon of water. This solution should be used almost every time you apply fertilizer to your houseplants.

For outdoor plants planted in the ground, sprinkle about 2 tablespoons (a medium handful) of Epsom salt around the base of the plant, avoiding direct contact with the main stem. After sprinkling, water the area thoroughly to help the salt dissolve and leach into the soil. For larger trees, a couple of big handfuls can be used.

Why it works

Epsom salt is primarily magnesium sulfate, providing two crucial nutrients: magnesium and sulfur. These elements are vital for healthy plant growth and tend to become depleted in soil, especially in potting mixes where plants have limited access to external nutrient sources. Magnesium and sulfur act as catalysts, helping plants to better absorb and utilize other macronutrients (like nitrogen, phosphorus, and potassium) that are essential for overall growth and production. Adding Epsom salt acts as a form of "insurance" to prevent deficiencies, leading to richer green foliage, stronger root and shoot development, and more abundant blooms.

For outdoor plants, the larger volume of soil acts as a natural buffer, making precise measurements less critical. However, for potted plants, where the soil volume is confined, consistent supplementation is more important.

Try it

1. For indoor potted plants: Mix 1 teaspoon of Epsom salt into 1 gallon of water. Use this solution to water your plants approximately every time you apply your regular fertilizer. This ensures a steady supply of magnesium and sulfur.
2. For outdoor garden plants: Take about 2 tablespoons (a medium handful) of Epsom salt and sprinkle it evenly around the base of the plant, making sure not to pile it directly against the stem. Water the area thoroughly to help the Epsom salt dissolve and be absorbed by the roots.
3. For larger trees: Use a couple of large handfuls of Epsom salt, spreading it around the drip line of the tree, and then water well.
4. Prevent salt buildup: Every third or fourth watering, use plain tap water without any additives to flush out any excess salts that might accumulate in the soil, particularly for potted plants.

Watch out for

• While generally safe, Epsom salt is a supplement, not a complete fertilizer. Continue to provide your plants with a balanced fertilizer that meets their primary nutrient needs.
• Always water thoroughly after applying Epsom salt to ensure it dissolves and is available to the plant roots, preventing surface crusting.
• Ensure your potted plants have good drainage to prevent waterlogging and excessive salt accumulation in the soil.
• Observe your plants for any signs of nutrient imbalance, although magnesium and sulfur toxicity from Epsom salt is rare when used as directed.