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Magnesium is a key nutrient for plants. Learn more about what magnesium does for plants and how to provide it in your garden.

Magnesium is a mineral that is often overlooked, but it is an important element for plant life. Magnesium helps to regulate the uptake of other essential nutrients and aids in photosynthesis. Without magnesium, plants can be stunted or they may not produce flowers or fruit.

Magnesium deficiencies are common in soil, so it's important to add this nutrient to your garden if you want healthy plants. There are many ways to supplement magnesium into your garden, so read on to find out how to get started!

What is magnesium?

Magnesium is a mineral that is found in soil and is important for plants. It helps to regulate the uptake of other nutrients and aids in photosynthesis. Magnesium is also necessary for plant growth and development.

What does magnesium do for plants?

Magnesium's major function is to serve as the central atom in a chlorophyll molecule. Without magnesium, there would be no chlorophyll. Green color plants owe their color to chlorophyll, but it does a lot more than that. Photosynthesis relies on chlorophyll.

Plants use photosynthesis to convert light, water, and carbon dioxide into energy (sugar) and oxygen. Plants require energy in order to develop and produce flowers or fruit. A plant will not be able to create enough energy without enough magnesium. The plant will cease growing when it does not have enough energy. It also aids in the activation of many plant cell enzymes needed for growth and contributes to protein synthesis.

Magnesium is required for the formation and maintenance of strong and good plant health. It also aids in phosphate metabolism. The importance of magnesium as a mineral has been recognized since ancient times. Magnesium assists with the transport of phosphorus through plant tissues. Plants require three primary nutrients: nitrogen, phosphorus, and potassium (NPK). Most plants require less magnesium than nitrogen, phosphorus, or potassium. However, it is still a vital mineral for plants to survive.

What causes a magnesium deficiency in plants?

A magnesium insufficiency in plants is sometimes caused by a magnesium shortage in the soil. This is more probable with sandy soil (as opposed to clay, which has more magnesium).

However, there are other possible causes of magnesium deficiency in plants. which are discussed below:

1. Lack of water

A lack of water has a variety of negative effects on plants, the most notable of which is that it causes wilting leaves. A lack of water can also result in nutrient insufficiencies in plants. Plants require water to obtain nutrients. After magnesium dissolves in water, plant roots absorb both the solution and the absorbed water through their roots.

Plants will not be able to absorb magnesium if there isn't enough water in the soil. This will result in yellow leaves and other signs of nutritional inadequacy.

2. Soil pH imbalance

Plants will not grow well in soil that has an insufficient or excessive pH. Plants can also develop a magnesium deficiency if the soil's pH is wrong. If your soil's pH is too low, add lime (calcium carbonate) to raise it. To prevent magnesium scurvy, use dolomitic lime instead of calcium carbonate.

3. Nutrient Imbalance

Excess nutrients in the soil, particularly nitrogen and potassium, can also induce a magnesium deficiency. When one nutrient is present in excessive quantities in the soil, it may prevent plants from absorbing additional essential elements. Too much calcium in the soil, for example, may prevent plants from absorbing magnesium.

Another reason for this is that magnesium and calcium have comparable chemical properties, which means they "compete" for uptake by a plant's roots. When there is too much calcium in the soil, magnesium loses this competition.

As a result, the plant becomes magnesium deficient. This can even occur when there is plenty of magnesium in the soil. You might end up with too much calcium in your soil if you apply too much lime (calcium carbonate) or other calcium-rich soil amendments.

4. Toxic Elements in the Soil

Toxic elements, such as arsenic, can also prevent a plant from absorbing magnesium. These toxic elements can bind to soil particles and form an insoluble compound. This will prevent the plant from being able to take up the magnesium from the soil.

If you think your soil might be contaminated with a toxic element, book a soil test by a soil testing laboratory. If the results show that your soil is contaminated, take appropriate action to remove or mitigate the toxic element.

5. Infrequent or inefficient fertilization

A lack of magnesium in the soil can also be due to infrequent or inefficient fertilization. When plants don't receive enough nitrogen, phosphorus, and potassium (NPK), they will not be able to absorb magnesium from the soil.

This is because magnesium is one of the nutrients that plants need in order to grow. If your plants aren't getting enough NPK, they will be unable to absorb magnesium from the soil.

Symptoms of magnesium deficiency in plants

1. Yellow leaves

This is one of the most common symptoms of magnesium deficiency. The leaves will start to turn yellow and then brown as the deficiency becomes more severe. In plants suffering magnesium deficiency, older leaves show interveinal chlorosis(dark green veins with yellow areas between them)

2. Wilting leaves

Magnesium is necessary for plants to maintain turgor pressure. When they are deficient in magnesium, plants will start to wilt.

3. Poor growth

If a plant is magnesium deficient, it will not grow as well as it should.  This will result in slow growth. It may be stunted or have a reduced number of leaves. The deficiency is often not directly visible but still negatively affects crop growth.

4. Dead patches

If the deficiency is severe, it can cause dead patches on the leaves.

5. Brown patches

Brown patches on the leaves are another sign of a magnesium deficiency.

6. Curling of the leaf edges

The leaves may start to curl up is a sign of severe magnesium deficiency.

7. Rust-colored spots 

The areas on the leaves that are affected by the magnesium deficiency will often be rust-colored.

8. Necrosis

The plant tissue in the leaves will start to die if there is a magnesium deficiency.

9. Poor fruit production

A magnesium deficiency can also affect the fruit production of a plant. The fruits may be smaller than normal or may not ripen properly.

10. Blossom end rot

Blossom end rot is a condition that affects the tomato plant and other fruit of plants. The bottom part of the fruit will start to turn black and rotten. This is often due to magnesium deficiency.

What is a good source of magnesium for plants?

If you need to add magnesium to your soil, there are several good sources you can use, and some of them are listed below:

1. Compost

Even if your plants don't have a mineral or nutrient deficiency, adding organic compost to the soil is a good idea. Compost increases the nutrient content of the soil while also providing organic material.

Over time, this natural stuff decomposes to give plants a long-lasting supply of nutrients. Organically derived substances also attract earthworms and helpful microorganisms to assist improve your garden soil.

2. Dolomitic Lime

Dolomitic lime is a form of limestone that has been altered by the addition of magnesium. The majority of dolomitic limestone is made up of magnesium (typically around 10% magnesium by weight) and calcium (usually around 20% calcium by weight).

If you want to add calcium or raise the soil pH while also adding magnesium to your soil, dolomitic lime is a good option.

3. Sulfate of Potash Magnesia

Sulfate of Potash Magnesia, often known as Sul-Po-Mag, has 11.2% magnesium, 22% sulfur, and 22% potassium by weight. This is an excellent option if you want to add potassium to your soil in addition to magnesium and sulfur.

4. Epsom Salt

Epsom salts are a form of magnesium sulfate. It is made up of 13% magnesium and 10% sulfur by weight. Epsom salts can be used to add magnesium to your soil as well as sulfur.

5. Magnesium Chloride

Magnesium chloride is a form of magnesium that has been combined with chlorine. It is made up of 31% magnesium and 17% chlorine by weight. Magnesium chloride can be used to add both magnesium and chlorine to your acidic soil.

6. Magnesium Nitrate

Magnesium nitrate is a form of magnesium that has been combined with nitrogen. It is made up of 21% magnesium and 16% nitrogen by weight. Magnesium nitrate can be used to add both magnesium and nitrogen to your acid soils.

In Conclusion: What can too much magnesium do to your plants?

While a magnesium deficiency can cause problems for plants, too much magnesium can also be harmful. If there is too much magnesium in the soil, it can interfere with the uptake of other nutrients, such as nitrogen, phosphorus, and potassium. This can lead to nutrient deficiencies. Additionally, too much magnesium can cause the soil to become too alkaline, which can be harmful to plants.

If you are concerned that your soil has too much magnesium, you can have it tested to find out. You can also add organic matter to the soil to help buffer the effects of excess magnesium.


  • I have some plants at my backyard (string beans, Chayote, tomatoes, and garlic) but very slow in growing and sometimes don’t produce much fruits and other don’t produce fruits at all. I know something is wrong how I’m doing my gardening. I need more info to learn to improved my hobby, please help.

    Cesar V. Cubcubin
  • very interesting and informative..


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