Using Epsom Salt in the Garden

Most people are aware that Epsom salt makes for a soothing bath if you have itchy skin or sore muscles, but did you know it’s also beneficial to some of your garden plants?

Why Epsom salt?

Epsom saltEpsom salt (magnesium sulfate) is high in magnesium.  Magnesium promotes the uptake of nitrogen and phosphorous from the soil.  Magnesium also promotes the creation of chlorophyll, the stuff that gives plants their green color and is essential for photosynthesis.  By improving photosynthesis the plant feeds itself better and stays healthier.  Magnesium also aids a plant in the production of more flowers, which in turn become fruit.  Boosting photosynthesis also boosts sugar production, so fruit trees and vines will produce sweeter fruit.

Before using Epsom salt it is recommended to have your soil tested for magnesium content; amending it may not be needed.

What Plants Benefit?

Most flowering plants can benefit from the use of Epsom salt.  This includes flowers such as roses.  But my focus is the vegetable garden, so I’ll confine my discussion to those plants.  The primary benefactors are the nitrogen hungry plants like tomatoes, potatoes, peppers, eggplant, cucumber, squash, and zucchini.  Do not use it on beans (which are nitrogen fixers) and leafy greens like lettuce, spinach, chard, and kale.

Signs of Need

magnesium deficiency grape leaf, epsom salt will help

Watch the plants leaves.  If leaves are shifting from green to yellow along the edges and between veins, it’s a sign that the plant is in distress and needs a boost.

Brown spots can also be a sign, but brown spots can also indicate other things such as blight or insect damage.  Healthy leaves are better at resisting disease and insect damage, so consider using Epsom salt as a periodic preventative measure.

How to Apply Epsom salt

There are two ways to apply Epsom salt: as a foliar spray and directly to the soil.

To make the spray, add 2 Tablespoons of Epsom salt to a gallon of water in a sprayer.  Shake or stir so it all dissolves.  Then once a month spray this solution directly on the leaves of your plants  in place of your regular watering.  It is best to do this in the morning before the sun gets hot.

Adding calcium (egg shell) and Epsom salt to a young tomato plant

The foliar spray works as a quick fix, but you can also add a 1 Tbsp of dry Epsom salt per 12 inches of plant height to the soil as a side dressing or worked lightly into the top of the soil above the plant’s roots.  Keep away from the stem.  Watering will dissolve the crystals and take the magnesium into the soil for the roots to pick up.  This works more slowly, but maintains over time.  Again once a month is plenty, don’t overdo this.

Either way, your plants will enjoy better health and produce more food for you.

Final note:

High applications of potassium or ammonium can induce magnesium deficiency symptoms in soil that originally contained enough magnesium.  Avoid excess nutrient (fertilizer) applications.

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