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Epsom Salt for Plants: Complete Guide

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All you need to know about using Epsom salt in the garden

Epsom salt for plants

You may have heard people talk about using Epsom salt in the garden. But does it help or hinder plants?

In this article, we’ll cover how Epsom salt works. We’ll look at whether it can be useful. We’ll also talk about how to use Epsom salt for plants – and when it could do more harm in your garden than good. This is your complete guide to Epsom salt for plants.

First of all, what is Epsom salt?

What is Epsom salt?

Epsom salt is a combination of magnesium, sulfur and oxygen – in other words, magnesium sulfate.

The name comes from the English town of Epsom in Surrey where magnesium sulphate was first discovered in the 17th century, in the waters of a natural spring. The mineral occurs naturally in lake beds, groundwater, seawater and limestone caves.

How does Epsom salt help plants?

Epsom salt is rich in magnesium. Micronutrients such as magnesium and iron help to keep plants healthy. They encourage the take up valuable nutrients such as nitrogen and phosphorus.

Epsom salt can make plant leaves greener by contributing to the creation of chlorophyll, which is vital for plants to gain energy from the sun.

Magnesium also plays a role in healthy flower and fruit production. So, a useful mineral to have around.

If your soil is rich with organic material though, you should already have enough magnesium. Plants only use small amounts of it.

Sometimes soil can get exhausted and become mineral-deficient, which is where adding magnesium comes into play. This is usually the case if you are a commercial grower, not a home gardener.

Which plants are helped by Epsom salt?

Epsom salt is often used in the cultivation of roses, tomatoes and peppers. Some gardeners find it useful in growing potatoes, carrots and lemons too. All of these plants love magnesium.

Are your plants lacking in nutrients?

Understanding your garden soil will help you to figure out what’s needed. A soil test can reveal nutrient deficiencies and imbalances.

If your plants are lacking magnesium, you could find Epsom salt of benefit. But it’s always useful to know what the soil is lacking before you try something.

Some plants suffer magnesium deficiency because the soil has too much phosphorus in it. Adding Epsom salt won’t help in this case, because the phosphorus level will still be too high. So our advice is to get your soil tested to see what’s missing.

It’s important to understand that Epsom salts are not nutrients. The core nutrients your plants need are nitrogen, phosphorus and potassium. 

Epsom salt can help your plants to absorb more of these nutrients, but it is not a general fertiliser and will not be useful if used in this way.

What does a magnesium deficiency look like?

If you notice that the leaves on your tomatoes look yellow, but the veins stay green, the soil might be lacking in magnesium.

Epsom salt for plants: How to use

Epsom salt is used in two ways – either watered into the soil or used as a spray on the foliage. In both cases, Epsom salt should be diluted in water. Use 1 tablespoon of salt to 1 gallon of water.

Which plants don’t like Epsom salt?

Epsom salt is useful in certain situations, but plants will grow just fine without its help. Beans, for example, can grow happily even when magnesium levels are low.

Here’s an interesting thing. You’ll see a lot of talk about how Epsom salt helps to stop blossom-end rot in tomatoes, but in fact, adding the salt could contribute to the problem. This is because blossom-end rot is caused by a lack of calcium.

Adding magnesium to the soil means the tomato plant will try to take up both minerals when it just needs calcium. In other words, the magnesium and calcium compete with each other.

As we said above, it’s worth getting a soil test to figure out exactly what nutrients you have in your soil, so you can make an informed judgement about what to do next.

Epsom salt for ferns and other house plants

House plants with yellowing leaves can benefit from Epsom salt solution if they are deficient in magnesium. Dilute using the following ratio: 1 tablespoon of salt to 1 gallon of water.

The easiest way to treat your house plants is with a spray. Spraying the leaves with the salt solution is thought to work faster than watering the soil to green up your plants again.

Always keep in mind that there are lots of reasons why a plant might have yellowing leaves. Make sure you cover the basics first, before reaching for a supplement.

Check that the soil or growing medium is rich in the right nutrients and that your plants are getting the right amount of water, heat and light.

Ways to avoid nutrient deficiencies

By making sure your garden and container soils are rich in nutrients at the start of every season, you shouldn’t need to reach for supplements.

Start each season by adding a general-purpose feed to your soil which is packed with nitrogen, phosphorus and potassium.

These are the three essential nutrients for plants. Add to this a good mulch of compost to get things going, and you should get excellent results.

Epsom salt for plants: 3 tips to take away

  1. Epsom salt can be useful for tired soil which is low in magnesium, where you want to grow magnesium-loving plants such as tomatoes, peppers, potatoes and carrots. The salt helps plants to absorb nutrients and makes leaves greener, which means plants can gather more energy from the sun.
  2. Epsom salt is not a fertilizer and shouldn’t be used as a blanket solution to yellow or wilting plants. Find out what nutrients your soil is mis by doing a simple soil test. Then you can address the imbalance by adding the right nutrients.
  3. You can use an Epsom salt spray on indoor plants such as ferns to help with yellowing caused by a lack of magnesium. But remember that Epsom salt doesn’t work as a fertilizer. Replenish essential nutrients by repotting house plants and using fresh compost.

Inspired to grow plants? Check these out:

21 Types of Evergreen Trees

30 of the Best Winter Garden Plants

The Complete Guide to Winter Greenhouse Gardening

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