Why Do Plants Need Calcium And Why It’s Important To Plant Growth?

Calcium may be one of the secondary nutrients for your plants. But this doesn’t, in any way, imply that it’s any less important than the primary nutrients. It is, in fact, as important as nitrogen, phosphorus, and potassium (primary nutrients), but the plants need it in lesser quantities.

But why plants need calcium? Well, as you might guess, if your garden doesn’t have enough of it for the plants, their health will suffer. Ultimately, you won’t get that vibrant green that you had been hoping to see. So, take action before it’s too late. Find out if your plants are getting the necessary supply of calcium (Ca). If they aren’t, use a good calcium fertilizer to add it to the soil. As simple as that!

How Does Calcium Help The Plants?

Starting with the fundamental question, why do plants need calcium (Ca)? Once you realize the true worth of this nutrient to your garden, you’ll be able to make sure the plants get enough of it to help them thrive. The most important thing that you should remember is that all plants need it to grow.

  1. Calcium helps build resistance in plants against diseases.
  2. It promotes fruit development and enhances the quality of your harvest.
  3. It activates certain enzymes that play a role in a series of cellular activities necessary for plant growth.
  4. The element also protects the plants against heat stress by enhancing stomata’ function and promoting heat shock proteins’ production.
  5. In the form of calcium pectate, calcium becomes a part of the plant’s cell walls. Since it’s a significant component of the plant’s tiniest components, it basically holds the plant together.

Insoluble Calcium Vs. Soluble Calcium

Calcium is a part of many types of minerals in the soil. Different forms of insoluble calcium compounds exist between the soil layers, but these aren’t available to the plants. The plants can only uptake the soluble Ca in the soil. Thus, plants growing in soils with high levels of insoluble calcium can also show a deficiency.

The positively charged calcium ions which get absorbed into the soil particles are called “exchangeable ions.” These ions can be exchanged by other ions in the soil solution to become available to the plants. Ca in the form of exchangeable ions is the one that’s useful to your plants, and that’s what a soil test will measure for you. Instead of measuring the soil’s total calcium, the soil test will let you know the level of “available” calcium in the ground.

Main Factors That Affect Calcium Availability To Plants

Since only soluble calcium helps your plants, it’s worth knowing some of the other factors that affect “available” calcium levels besides true calcium deficiency in the soil.

Cation-exchange Capacity

Cation-exchange capacity or CEC measures the quantity of positively charged exchangeable ions that the soil can carry. A higher CEC suggests that the ground has a more considerable ability to hold calcium ions, making more calcium available to the plants.

Soil’s pH

Soil with a higher pH will usually have more available calcium. But, this isn’t always the case. Excess calcium in alkaline soil fuses to phosphorus, making this essential macronutrient unavailable to the plants, so you’ll need to be careful.

Presence Of Other Cations

Since calcium ions compete with other cations to become a part of the soil solution, too many cations will make it less available to the plants. This is particularly true for sodium ions since they replace calcium ions readily, inhibiting their availability to the plants. Ensure there’s a right balance of nutrients to be available to the plants in the ideal quantities.


Plants will only uptake calcium that’s a part of the soil solution. Lack of moisture will also prevent the plants from absorbing it.


Low temperatures will inhibit the plant’s ability to uptake it.

Transport Of Calcium Inside The Plants

Calcium isn’t mobile within the plants. Plants depend on transpiration to transport calcium from the soil to the roots and then to the plant’s new stems and leaves.

In transpiration, plant roots absorb the soil solution, which contains calcium and many other valuable nutrients. The soil solution is then transported to the new growth appearing in the plant. Here, calcium will be utilized as a building block for the new shoots. Simultaneously, the excess water vapor will be evaporated through the tiny holes in the leaves called stomata.

Factors that slow down transpiration, such as low temperatures and high humidity, will hinder calcium availability to the plants. This is why calcium deficiency is usually seen in early spring when the soil temperatures are low. Also, it initially affects new growth since these parts transpire less.

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Symptoms Of Calcium Deficiency In Plants

Symptoms of calcium deficiency usually begin to appear in young leaves and fruits since they transpire less water. Since plants use calcium to build new tissues, the lack of it will result in distorted or stunted growth in the new leaves and stems. Here are some other symptoms that suggest calcium deficiency:

  1. Necrosis near the edges of the leaves.
  2. Chlorosis in the new leaves, in the form of blotches.
  3. The black heart in celery typically comes from calcium deficiency.
  4. Brown spots, starting around the edges of the leaves, spreading to the center.
  5. Tip burns on the inside of cabbages are a symptom associated with calcium deficiency.
  6. Blossom-end rots are common in plants with calcium deficiency, particularly tomatoes, cucumbers, and peppers.

You can also read our post – Identifying And Removing Bugs From Your Indoor Garden, to learn more about other plant problems, especially those associated with houseplants.

How To Fix Calcium Deficiency In Plants With Organic Solutions?

Adding crushed eggshells to the soil offers an excellent source of calcium. Mix it in your compost for uniform distribution in the ground and the added benefits of organic material that’s a part of the compost.

Some gardeners plant tomato seedlings in eggshells directly in their garden without removing the eggshell. This technique helps prevent blossom end rots in tomatoes. Wood ash and bone meal are also good organic sources of calcium.

Good Inorganic Solutions

The most popular approach to raising your soil’s calcium levels is to add lime to it. Apply lime somewhere in autumn so that calcium is available to your plants in time.

Chemical fertilizers are also available for correcting your soil’s calcium deficiency. But, not all fertilizers contain calcium, so you’ll need to read the product label carefully! And remember to make sure that the fertilizer you choose has a calcium level below 200 ppm. An excess amount of calcium can make other vital nutrients less available to the plants.


Water is an excellent source of calcium, although it’s often overlooked. All sources of water offer some calcium. Water from deep wells and non-coastal areas of North America is especially abundant in calcium. If your water comes from one of these sources, the chances are that the plants are already getting ample calcium for healthy growth.

In contrast, water from rain, rivers, ponds, and coastal areas may not offer enough calcium to cater to your plants’ needs. In this scenario, you’ll need to have the water tested to be sure. With a calcium level in water above 40-60 ppm, you won’t need to make any extra calcium application to your lawn/garden.

Applying Foliar

Foliar application is a quick fix if a plant is showing calcium deficiency symptoms. Spraying calcium to leaves directly makes it available to the parts where it’s needed. Make a dilute solution of about 1 ounce (about 30 milliliters) of calcium nitrate or calcium chloride to a gallon (about 3,8 liters) of water. Spray the liquid to the plants, making sure they cover all the new growths.

Is Calcium Toxicity In Plants Possible?

Excess calcium doesn’t usually cause toxicity to the plants directly. But it does reduce the availability of other essential nutrients that also exist in the form of cations. When excess Ca becomes a part of the soil solution, other exchange ions are less available to the plants.

For example, high calcium levels will often compete with potassium and magnesium uptake, causing the deficiency of these nutrients in plants. If this happens, you should stop any applications of calcium right away. Instead, look for fertilizers that contain the nutrients that the soil lacks and apply them to your garden.

Make sure that your plants are growing at an optimal pH. Most plants appreciate a neutral pH, as it will make the most nutrients available to them.

Final Words

Do you now understand why plants need calcium? It is vital to plant growth, just like all the other nutrients, which should also be a part of your plants’ diet. Fortunately, it’s easy to identify if your plants need calcium and even easier to ensure that your plants get enough of the element for their healthy growth.

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