Determining the Cause of Cal Mag Deficiency in Plants

Last Updated on October 8, 2022 by Real Men Sow

If your plants look unhealthy and you suspect they may be suffering from a Cal Mag or Calcium Magnesium deficiency, it’s essential to take action to restore their health. But before you can do that, you need to identify the cause of the deficiency.
Once you know what is causing the deficiency, you can take steps to correct the problem and help your plants to thrive.

Causes Why There’s Cal Mag Deficiency in the Plant?

Cal mag deficiency is when garden soil is too sandy or coarse. It can also be caused by RO treatment or heavy phosphorus-based fertilizers. Other than these, low transpiration and pH imbalance can also be generated. 

A Highly Acidic or Alkaline Soil

Calc Mag deficiency is most common in soil that is highly acidic or alkaline. You may notice curled edges and yellow spots on the leaves.

The plant will struggle to absorb calcium and magnesium in acidic soil. However, plants that live in alkaline soils can absorb them easily. The plant can only thrive with nutrients intact if it is within the pH range of 6.5-7.5.

Nutrient Imbalance Causes Cal Mag Deficiency

There is a high chance that your plant will develop a Cal Mag deficiency if you are not paying attention to its needs. To survive, plants need to have the correct balance of nutrients, including sodium, potassium and aluminium.

Because of their combined ability to bind calcium and magnesium to plant cells, excesses of any one type of nutrient can lead to deficiency or over-saturation. This condition will also cause stunted or slow root, shoot and apical growth, and limp stems with no vitality.

Low Transpiration Rate

A plant with a lower transpiration rate has less water evaporating from its leaf and flower pores. The plant cannot efficiently transport nutrients from the roots through the shoot, leading to a deficiency.

Low transpiration rates are caused by high humidity, cold weather, and insufficient watering. If you over-exposed your plant to cold or keep it in a dry environment with too much moisture, it will most likely develop a deficiency.

Use of Treated Water Cal Mag Deficiency

Do you use reverse osmosis or distilled water to water your plants? This is another reason why your plant may become deficient.

Rainwater and tap water contain essential calcium, and magnesium, aiding plant growth. These nutrients are removed by reverse osmosis treatment or distillation, which can lead to deficiency.

Using Soft Water

Although soft water can keep your plants alive, it might not be the best option. Soft water has a lower pH and little to no calcium or magnesium. Hard water, on the other hand, has a higher level of calcium dissolved minerals that can reduce the chance of a deficiency.

Sandy Coarse Soil Cal Mag Deficiency

Use sandy soil, coco coir or coarse soil as your planting medium. It has lower levels of calcium and magnesium than loamy and clayey soils. Minerals are more abundant in clay particles that are larger than others.

How To Fix Cal-Mag Deficiency

Address the PH Imbalance

Adjust the pH to the right level to ensure your plant stays healthy. To increase pH in acidic soil, you can add lime. If the soil is too acidic, you can also add gypsum and bone meal. To check the soil’s pH level before you make any changes, you can always use a test tool.

Provide Well-balanced Nourishment

To aid in calcium and magnesium absorption, fertilize the right side of the plant. Avoid phosphorus-based fertilizers, especially for non-flowering plants. This will cause excessive calcium to be absorbed into the soil. For a balanced fertilizer, flush the plants with pH-neutral waters and then apply a well-balanced formulation.

Manage Low Transpiration Rate

Plants need to have a lot of moving air to increase transpiration and lower the risk of developing a deficiency. The plant should be kept in an area that is well ventilated and where there is constant air movement. The plant should be watered regularly to allow calcium to reach the leaf.

Use the Right Water

Tap water, hard water and rainwater are more suitable than treated RO, soft, or distilled water.

Manage Climatic Conditions

High temperatures and humidity can also cause conditions of deficiency. The plant should therefore have moderate heat and humidity. Indoors, use a humidifier to reduce humidity and place it in diffused partial sunlight. Outdoors protect the plant against extreme temperatures such as direct sunlight and chilly winds.

Use Pre-mixed Cal Mag Deficiency Supplements

Pre-mixed cal mag deficiency supplements can be purchased at reputed online stores and gardening shops. Pre-mixed supplements come in different sizes, so choose the one that is best for you.

For the correct application, follow the manufacturer’s directions. You should also ensure that the supplement is properly absorbed and properly balanced.

Check Soil Before Adding Supplements

Check the soil for signs of a cal mag deficiency, such as reduced growth or discolouration. You may not have enough calcium or magnesium in your soil, but the signs could indicate something more.

Home Made Cal Mag Deficiency Supplements

To overcome the deficiencies, it is simple to make homemade supplements. Mix Epsom salts (which chemically are magnesium sulfate) with calcium nitrate in the ratio 1:1.5. This will give you 0.15 ounces (4.5g) of Epsom salt, and 0.2 ounces (6g) of calcium nitrate for every gallon of water.

Calcium intakes that are slightly higher than normal can help keep older leaves healthy and prevent root rot.

Organic Matter as Supplements for Cal Mag Deficiency

The organic matter listed below can be used as well.

  • Calcitic lime: This is a high-calcium carbonate calcium fertilizer that will not only increase the pH but also add calcium to the soil. If your soil pH is low and acidic, this is a good option. Check your soil pH before you apply calcium lime. It may not be very helpful if the soil is acidic or low in pH.
  • Dolomitic lime: This is a mixture of calcium carbonate and magnesium carbonate. It raises pH levels, similar to calcitic limestone. Do not use it unless you have checked your soil.
  • Gypsum: A calcium sulfate-rich substance that naturally occurs in the earth. It can be used to supplement calcium in plants.
  • Calcium EDTA (Water-soluble calcium): EDTA is a calcium-soluble form of calcium. It does not react with other elements in the soil and does not leach.

Home-based organic supplements for Cal Mag Deficiency

These quickly found organic matter can be used to make your supplement.

  • Bone meal: A fine powder made from crushed bones and is high in calcium and phosphorus.
  • Crab Meal: Again, this product is a fine powder made from crabs and crustaceans. It can provide the plant with 10 to 20% calcium.
  • Eggshells: Powdered eggshells are a great source of calcium carbonate, especially indoor plants.

Monitor Your Plants

You should monitor your plants by regularly testing the soil for calcium or magnesium. This preventive measure will help keep your plant’s foliage healthy.

Signs That Your Plants Have Cal Mag Deficiency

Curling Leaves

The curling of new plant growth is a classic sign of calcium deficiency. These are commonly called parachute leaves. It is caused by a deficiency of calcium in the plant.


You may notice yellow spots on the leaves, brown edges, and tips. Another sign of calcium deficiency is yellow spots on leaves and brown tips and margins. You should also note that discolouration can be a sign of other problems. Before you diagnose a calcium deficiency, do a simple soil test.

Slow or Stunted Growth

A cal mag deficiency may cause your plant to take a while to reach height, bloom and spread its leaves. To determine if your soil is deficient, check it and then take the necessary steps as described in our care section.

Rotten Fruits and Flowers

If a plant produces rotten fruits and flowers, it is likely that the plant has a calcium problem. If you notice rotten blossoms, smelly root rot, or rarely blooming flowers, it’s time to take action and restore minerals.

Limp Stems

In the event of a deficiency, shoots and stems can become weak and lose energy. The leaves fall before the time and don’t stay at the node. The terminal buds also die eventually because they don’t stay up.


If your plants have the symptoms above or are experiencing cal mag deficiency, then you should aid your plants in replenishing the needed minerals. Don’t worry if it’s too late to fix things this season; as long as you identify this issue early enough next season, you’ll be prepared to prevent future problems.

Real Men Sow
Real Men Sow

Hello, I’m Pete and I’m currently based in the west of Scotland, in a small place called Rosneath, where I’m exploring my garden adventures. I personally started gardening around 6 years ago and initially, I started out by growing my favorite fruits and berries, such as strawberries, Raspberries & Gooseberries. Since then I’ve added a lot of vegetables and working closely with my neighbor, it’s been a lot of fun.