5 Ways to Effectively add Calcium to Tomato Plants

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Quick Answer: How To Add Calcium To Tomato Plants?

Calcium is one of the vital nutrients essential for tomato plants. Its deficiency may cause blossom end rot, necrosis, stunted growth, and poor fruit development. You may add crushed eggshells, wood ashes, gypsum, and powdered lime around the base of the plants. You may also use calcium spray. But its effectiveness is inconclusive.

This is a detailed guide on various ways to add calcium to tomato plants effectively.

I have personally tried and tested many of these methods, for others, I have relied on the insights provided by experts and research papers.

I have also incorporated the insights of my fellow gardeners.

Shall we read further?

Why Calcium is Critical for Tomato Plants

Calcium is one of the key nutrients required for holding the structure of cell walls and influencing salt balance within cells.

It enhances pollen germination and influences the growth of cells. It also helps in moving the nutrients and extending the main root system.

It plays an important role in fruit quality.  It is also needed for the fruit set to develop properly.

Table: Effect of Calcium on Different Growth Stages of Tomatoes

Stage of growthEffect of calcium
During establishmentIncreases root and leaf growth
During vegetative growthPromotes strong plant growth, balance moisture, and nutrient uptake
ReproductionMaximizes reproductive development
Fruit ripening to MaturityQuality of fruits, firmness, and prevents blossom end rot.

Its deficiency causes Blossom End Rot which forms a brown or black spot on the bottom of the fruit.

It may also cause necrosis, stunted growth, and poor fruit production

When To Add Calcium To Soil?

The best way to check for calcium deficiency is to get a soil test for Cation Exchange Capacity.

Cation Exchange Capacity is the relative ability of the soil to absorb nutrients, including calcium in the form of ions.

The higher the CEC, the more organic matter in your soil. The soil may hold more water and calcium.

Lower CEC indicates that soil is likely to lack nutrients.

The soil test at home will help to determine the amount of calcium and soil acidity.

How To Add Calcium To Tomato Plants?

There are several ways to add calcium to the soil for tomato plants. I have discusses a few below.

1. Eggshells and Shell Meals

One of the popular ways of adding calcium to the tomato plant is by spreading crushed eggshells or shell meals around the plants. You may add them to compost or prepare tea. You may also use eggshells as a foliar spray.

The natural sources of calcium are crushed eggshells and shell meals. Eggshells are hard structures made entirely of calcium carbonate.

I often use powdered eggshells for my tomato plants.

Shell meal is the ground shells of marine animals. You may purchase shell meals at nursery or garden stores.  

How to add Eggshell or Shell Meals

Time Taken: 15 minutes

What You Need

  • Eggshells or shell meals
  • Water

Step by Step Process to Add

  1. Crush the eggshells and add them to the soil – You may clean and dry the eggshells. Apply crushed eggshells or shell meal to the soil around the tomato plants. This helps in maintaining a steady calcium level during the growing season.
  2. Add crushed eggshells to the compost – The crushed eggshells may be added to the compost and later added to tomato plants. It may enhance tomato growth and yield. 
  3. Prepare the eggshell tea – Boil a gallon of water and add 10 clean dried eggshells. Let the shells sit in the water overnight and strain them. The prepared concentrate may be added directly onto the soil.
  4. Add calcium foliar spray – Another way of adding calcium is making a foliar spray using eggshells. You may boil 20 eggs in a pan with a gallon of water.
  5. Remove from heat and allow it to cool. Strain the water and spray it on the tomato plants.

Here is a video on using eggshells as fertilizer for tomato plants:

2. Wood Ash

Wood ash helps in making the soil less acidic. It helps in adding calcium when sprinkled around the base of the tomato plants. You may also use wood ash tea.

Wood ash is the organic residue left after the combustion of wood. One of the important elements in wood ash is calcium (about 25-45 percent).

It also has potassium, phosphorus, and magnesium.

It helps in adding calcium to the tomato plants. It also helps in deterring snails and slugs. Avoid using ashes from treated woods.

How to Add Wood Ash

Time Taken: 10 mins

Step by Step Process to Add

  • Spread wood ash around the tomato plants – Keep the ash dry. You may sprinkle the wood ash around the base of the plants. Avoid getting it on the leaves to prevent unwanted damage.
  • Add to the compost – You may add wood ash to the compost pile and later added to the plants.

Make wood ashes tea – Add five pounds of wood ashes in a permeable bag. Soak it in a 50-gallon garbage can filled with water. Let it sit for four days and then pour it around tomato plants once a week.

3. Gypsum

You may use gypsum to add calcium to the tomato plants if the soil pH is correct. Sprinkle around the base of the plant and water them to help with absorption.

Gypsum or calcium sulfate is a natural calcium source. It is available in granular or powdered form. 

You may add them to the soil if the plant is not getting enough calcium and the soil pH is correct. It may be easily absorbed by the plants without affecting the acidity of the soil.

How to Add Gypsum

Time Taken: 15 minutes

What You need

  • Gypsum powder
  • Water

Step by Step Process to Add

Sprinkle the gypsum powder around the plants – You may spread gypsum powder around the tomato plants.

You may need to water the area after spreading to help with the absorption into the soil.

4. Powdered Lime

Powdered lime may be added to the soil of tomato plants. It helps in altering the soil pH. Dolomite lime may help in adding magnesium along with calcium.

Few gardeners suggest using powdered lime or calcium carbonate to alter the soil pH. It is preferable to use fast-acting lime and work it in the top 12 inches of soil.

You may have to wait for a long time for soil pH to change if using other forms of lime. Do not add lime if the soil pH is already correct.

Another variation of powdered lime is dolomite lime. It also contains magnesium that may be useful if the soil also has low levels of magnesium.

How to Add Powered Lime

Time Taken: 15-20 minutes

What You Need

  • Dolomite lime

Step by Step Process to Add

Spread dolomite lime – Spread 2 to 3 pounds of dolomite lime per square foot of the soil. You may use a rototiller, spade, or rake to incorporate the lime into the soil. Water the soil later after applying the lime.

5. Calcium Spray

Calcium spray may be used to spray diluted calcium nitrate or calcium chloride to the tomato plants. However, it is a less effective way of adding calcium to tomato plants.

Another option to add calcium to tomato plants is the use of calcium spray. It involves spraying the leaves of tomato plants with calcium nitrate or calcium chloride. 

You may spray calcium two or three times per week after the second set of flowers bloom.

How to Use Calcium Spray

Time Taken: 15 minutes

What You Need

  • Calcium nitrate
  • Water

Step by Step Process to Add

Prepare the foliar spray– Mix two to four tablespoons of calcium nitrate in a gallon of water. Shake well until the granules have dissolved.

Spray the plants– You may apply a tablespoon of calcium nitrate to moderately-sized plants.

Click this video on how to make a calcium spray for tomato plants:

However, it is considered a less effective way of getting calcium to the plants.

The research suggests that the spraying of calcium to correct a deficiency is inconclusive.

Also, the plant can not move the calcium from the leaves to the developing fruit.

Also, it is impermeable to water once the fruit has grown to a golf ball size. It may be due to the development of the outer waxy layer.

It is recommended to supply calcium through the irrigation system.

Calcium nitrate is a water-soluble form of calcium and nitrogen that may be injected into drip irrigation systems. 


How to know if your tomato plant needs calcium?

Tomato plants may show distorted leaves, yellow patches, and stunted growth when they are deficient in calcium. You may observe blossom dropping, weaker stems, and blossom end rot.

How does calcium get to the tomato fruit?

Tomato needs calcium to grow and make the fruit firmer. It cannot mobilize enough calcium to the fruit. It relies on transpiration for the immediate supply of calcium in the xylem. If there is a lack of transpiration or fruit grows quickly, calcium does not get into every part of the fruit.


I hope this article has helped you with different ways to add calcium to tomato plants.

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