How does epsom salt affect plant growth?

Question:

How does epsom salt affect plant growth?

Hardiness Zone: 1

Young City from Augusta, GA

Answer:

Young City,

This is a great question, because although Epsom salt can be beneficial to plants, it isn't always in the way that gardeners think. Usually Epsom salts are sold as a fertilizer component or used as a tool to change soil pH.

Here's how it really affects plants:

Epsom salts contain two elements important for plant growth-magnesium and sulfur. Magnesium helps form chlorophyll in plants and is essential for photosynthesis. Magnesium is present naturally in the soil and is also found in organic fertilizers. Sulfur helps activate many plant proteins and enzymes needed for growth. It helps plants resist the cold, assists in root production and seed growth. Sulfur is often delivered to plants in the form of rainwater.

The claim is often made (at least by the folks selling it) that plants are usually deficient in these two elements. Not so. Some plants, like chrysanthemums and gardenias for example, do sometimes carry high levels of magnesium in their leaves, and can benefit from having high levels of magnesium in their soil. In the case of most plants, however, soil usually contains enough of these elements that adding Epsom salt is unnecessary.

Soils that lack magnesium tend to be acidic. Epsom salt is actually considered a neutral salt, meaning it has very little effect on a soil's pH. In cases where a soil is acidic, it's better to add dolomitic lime if you want to increase the pH. IF it turns out that the soil is deficient in magnesium but the pH is fine, THEN it's better to add Epsom salt to increase the magnesium levels because adding it will not alter the pH.

Epsom salts are a good way to deliver sulfur and magnesium to plants. If your plant is low in either of these nutrients, adding Epsom salt can be beneficial. In most cases, however, low magnesium goes hand in hand with soil acidity. In these cases dolomitic lime is more appropriate than Epsom salts as a way to add magnesium, while raising soil pH.

It's best to test your soil before adding Epsom salts or you may end up wasting your time, or even making things worse.

Ellen