Epsom salt, also known as magnesium sulfate, is a popular home remedy used by many gardeners to help plants grow. While it can provide numerous benefits to plants, such as improving flower blooms and enhancing a plant’s green color, epsom salt doesn’t benefit all plants. Some plants are sensitive to the high amounts of magnesium and sulfur found in epsom salt and can suffer adverse effects if it is applied to their soil or foliage.
Plants That Are Sensitive to Epsom Salt
Here are some of the key plants that should avoid being treated with epsom salt:
Azaleas and Rhododendrons
These flowering shrubs thrive in acidic soil and do not tolerate the magnesium in epsom salt well. Applying epsom salt to azaleas and rhododendrons can result in magnesium toxicity, causing the plants to become nutrient deficient and experience yellowing leaves.
Hydrangeas are another acid-loving plant that can suffer adverse effects from epsom salt. Too much magnesium absorption leads to yellow leaves, poor flowering, and other signs of magnesium toxicity. For hydrangeas to bloom their best, an acidic soil pH below 6.0 is ideal.
Tomatoes and Peppers
Tomatoes and peppers thrive in slightly acidic soil and do not respond well to epsom salt. It may cause foliage burn, blossom end rot, reduced fruit yields, and magnesium toxicity. Tomatoes and peppers are also prone to magnesium deficiency in alkaline soils above a pH of 6.5.
Beans and Peas
Beans and peas prefer slightly acidic to neutral soil. Epsom salt makes the soil more alkaline and results in magnesium buildup, preventing the ideal uptake of nutrients like nitrogen and potassium. This leads to yellowing leaves, stunted growth, and lower bean and pea yields.
Strawberries, blackberries, and raspberries grow best in slightly acidic soil, as do blueberries. Epsom salt raises the soil pH too much for optimal growth and production. The magnesium in it can lock out other nutrients, leading to leaf yellowing and fewer berries.
Reasons These Plants Don’t Respond Well to Epsom Salt
Sensitive plants like azaleas, blueberries, tomatoes, and beans don’t benefit from epsom salt for the following reasons:
It Raises the Soil pH
Epsom salt makes the soil more alkaline, and the plants mentioned prefer acidic conditions. Even a slightly higher pH can limit their ability to absorb nutrients like nitrogen, phosphorus, and potassium. Abnormal pH affects all plant functions.
Causes a Magnesium Buildup
The high amount of magnesium in epsom salt can overaccumulate in the soil. This leads to magnesium toxicity, causing yellow or reddish leaves, poor flowering, and stunted growth. Excess magnesium also prevents the uptake of important minerals like calcium and potassium.
Leads to Salt Damage
Epsom salt is high in sulfates. When overapplied, it accumulates in the soil and causes salt stress for sensitive plants. High salt levels dehydrate plant roots and leaves and caneven lead to plant death.
May Lock Out Other Nutrients
Magnesium and sulfur interact with other soil nutrients. High levels of these minerals can tie up phosphorus, calcium, potassium, nitrogen, manganese, iron, and other nutrients that plants need. Nutrient imbalances or deficiencies affect plant growth.
Negatively Impacts Root Zones
Some plants are extremely sensitive to chemicals and compounds applied near their roots. Epsom salt changes the soil environment, which can damage delicate root hairs, inhibit further root development, and allow root diseases to develop.
The Best Uses for Epsom Salt in the Garden
While epsom salt isn’t ideal for the plants mentioned, it can serve many valuable uses in the garden:
Encourage blooming and enhance flowering when applied to roses, hibiscus, and other ornamentals.
Increase vegetable yields for magnesium-loving plants like potatoes, carrots, radishes, turnips, and cabbage.
Boost peppermint, echinacea, St. John’s Wort, and other medicinal herb growth. The magnesium improves their medicinal properties.
Help potted plants by adding a teaspoon per gallon of water once a month. The magnesium prevents chlorosis.
Treat magnesium deficiency symptoms like yellow vine leaves.
Increase sulfur levels to lower pH in alkaline soils.
Promote vigorous leaf growth and strong plant cell development.
Key Takeaways on Epsom Salt and Plants
- Epsom salt provides magnesium and sulfur but can adversely affect acid-loving plants like blueberries, azaleas, rhododendrons, hydrangeas and certain fruits and vegetables.
- It’s best to test soil before using epsom salt. Only apply it if the soil is deficient in magnesium.
- For plants sensitive to epsom salt, use an acidic fertilizer specially formulated for them, improve drainage, amend soil pH, or use an organic citrus fertilizer.
- Epsom salt is beneficial for plants that thrive in neutral to alkaline soils and need more magnesium for flowering and fruiting.
So in summary, epsom salt is a useful treatment for some plants but should be avoided on others that prefer acidic soil environments. Check that it is suitable for your particular plants before using it in your garden.