Calcium Deficiency in the Garden: How to provide calcium?

Last updated on October 23rd, 2023 at 08:18 pm

Today I want to comment on a problem that appears from time to time in our crops, calcium deficiency and how to solve it with organic methods to not lose productivity in our garden or its organic character.

Calcium Deficiency in the Garden: How to provide calcium?
Rotten butts in tomato can occur both early and late.

Calcium in plants

Calcium Deficiency in the Garden: How to provide calcium?

Calcium is an essential macronutrient for the growth of our plants but unfortunately, although it can be found relatively easily in the soil, it is not a very mobile element (it is present in the substrate but in low solubility structures so its concentration in the soil solution is relatively low) and the absorption of calcium by plant roots is difficult.

The functions of calcium are varied, mainly it is a structural element as it is part of many tissues, from cell membranes to the middle lamina, it regulates the opening and closing of stomata and contributes to the ionic balance of the plant by moderating the effects of sodium salinity, allowing cultivation in partially saline soils by reducing its toxic effects. This is why a marked deficit of this element can be very detrimental to our crops in the orchard.

What is calcium deficiency: Symptoms

If the growth of our plant is very high, situations of shortage of this nutrient can occur. To know the symptoms of calcium deficiency it is necessary to observe well the growth areas of our plant such as leaves or fruits.

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In these areas the calcium requirement will be higher as they are young structures that are continuously creating new tissues, and if this demand is not met, the tissues may become deformed, acquire a blackish-brown appearance or slow down in root and apical development, leading to a loss in the productivity of our plant.

Calcium deficiency is a common problem in our gardens, the best known case could be the soft rot that appears in the apical end of tomatoes, known as peseta or smoked, but it also affects other crops such as celery (forming a black heart), lettuce (drying the edges of the leaves) or watermelons and melons (appearing cracks on the surface of the fruit).

Calcium Deficiency in the Garden: How to provide calcium?
Here we see the appearance of soft rot in tomato

How do plants absorb calcium?

To alleviate calcium deficiency in our garden we must first learn how our plants take calcium from the soil. Calcium is found in the soil as part of other mineral compounds (insoluble for plants) such as silicates, carbonates or phosphates. It also appears in the organic fraction of the soil and as a free cation Ca2+, the form available to the roots.

Our plants take up calcium along with water through the roots. This dissolved calcium will move through the plant according to its water needs and its level of transpiration (imagine that the plant sweats like us), so in situations of high temperatures calcium will move with water to the areas that require more transpiration (you are hot and sweat), these areas are the young tissues or with more surface exposed to the sun, the leaves, the calcium lost in the leaves by evaporation does not reach the fruits, so this calcium deficiency occurs.

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On the other hand, a low level of transpiration can also cause calcium deficiency as well as a long period of drought. Therefore, calcium deficiency in the garden is more related to the water stress of the plant than to the content of the nutrient in the soil.
How to provide calcium to plants and soil?

To alleviate calcium deficiency in our plants there are several simple and inexpensive methods.


The most common is to crush an eggshell and bury it in the soil in the place where we are going to plant our plant. In this way a calcium contribution is added to the soil, although minimal since it is added in a very little soluble form for plants (calcium carbonate CaCO3), if your soil has a slightly acid ph the eggshell will decompose better, if not you can always macerate it in a mild acid such as vinegar to release some calcium before adding it.

Calcium Deficiency in the Garden: How to provide calcium?

By crushing and adding an eggshell to the soil, we can alleviate calcium deficiency

Calcium oxide

If your soil is somewhat basic it will already be rich in salts containing calcium, if you still observe absorption problems, it is most likely that there is calcium in the soil but not in a form available to your plants. In this case you should amend the soil with calcium oxide (CaO).


We can also dilute a glass of milk in 1 L of water and add it to the affected plant with a sprayer or add powdered milk directly to the soil or on the leaves, with a few grams every 15 days is more than enough. There are people who use special pills like the ones recommended for osteoporosis and they say that they work well.

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Control the watering of the plants 

In any case these remedies are extreme, to control that the calcium supply in our plants is correct we must pay attention to the irrigation of our garden so that there is no water stress and our plant does not suffer calcium deficiency. Remember to give frequent waterings in summer and never in the hottest hours of the day.

Do not miss this video tutorial where we talk about the calcium problem in tomatoes and how to solve it:


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.