Knowledge from Olle Garden Bed: Four Signs of Calcium Deficiency in Plants and How to Address Them

From roots and shoots to seeds and fruits, calcium is an essential nutrient that plays a crucial role at every stage of plant development. Read here are some things that you should know when It comes to Olle Garden Beds!

Calcium is a versatile mineral, more so than any other nutrient. It greatly promotes overall plant health, aids in robust growth, and facilitates nutrient uptake. It creates strong roots, builds healthy soil, and oversees immune responses in times of trouble.

Providing the right amount of calcium to plants affects every segment of their journey, from seedlings to fully mature varieties. By measuring your calcium levels correctly, you'll be on your way to a successful and thriving garden.


Why Calcium Is Crucial for Your Garden

After over a century of research, we now have a current understanding of calcium's role in plant health. It involves many intricate mechanisms that keep plants growing.

Here are the fundamental ways in which calcium supports healthy plant life:

Plant Morphology and Structure

Calcium is responsible for the development of strong physical structures in plants - branches, leaves, and fruits - rather than just green, watery blobs.

It plays a major role in the formation of plant cell walls and cell membranes, affecting their pliability, integrity, and permeability. It acts like cement, holding everything together, keeping the plant's shape sturdy, thick, and rigid.

Nutrient Transport

Calcium also has a significant impact on the transport and absorption of other essential nutrients.

As a resident cell wall fortifier, it maintains a high-speed nutrient highway within the plant (the xylem and phloem) for efficient movement of water, nutrients, and sugars from the roots to the tips of the leaves.

Root Development

Calcium is behind various cellular processes that promote the growth of strong and extensive root systems.

Certain proteins rely on a supply of calcium to enable proper division and elongation of root cells. This is particularly important for the formation of root hairs, tiny lateral growths along the root tip. These hairs significantly increase the surface area of the roots, allowing them to make better contact with the soil and absorb more water and nutrients.

Reproductive Health

Calcium is crucial for a plant's ability to complete its life cycle.

It is necessary for the development of pollen tubes and the vitality of pollen grains. It is involved in the process that enables fertilization between a plant's male and female reproductive organs.

Once a plant is pollinated, calcium enhances the cell walls of developing seeds and aids in the formation of seed coats.

In the case of fruiting plants, calcium is crucial for the highest quality harvest. Its role in cell wall strength creates fruits with firm, thick skin and solid flesh.

Immune Response

In addition to its role as a structural engineer, calcium is also a so-called intracellular second messenger. When external physiological and environmental cues are met, it transmits signals that trigger a series of events for deploying internal plant defenses.

Calcium is one of the substances that responds earliest to pests, diseases, and other stressors. Calcium signals initiate a range of protective measures, from defense gene expression and stomatal closure to the callusing of wounded sites and programmed cell death at infection sites.

Overall, plants that have consistent access to calcium have higher stress resistance, preventing significant damage in the first place. Pests and pathogens are more likely to attack soft or weakened tissue, but calcium fortifies plant cell walls and repels invaders.

Soil Fertility

Just as calcium is crucial for plants, it's also an important mineral for soil health.

Calcium aids in soil cation exchange capacity – the ability to hold and release positively charged ions (cations) like calcium, potassium, magnesium, and iron for plant use when needed.

It also helps establish healthy soil structure through soil aggregation. Calcium ions bind soil particles into tiny clumps, creating space and channels for air and water movement within the soil.

It's also a necessary nutrient for soil life. Beneficial microorganisms – bacteria, fungi, algae, and protozoa – require a diet rich in calcium to grow, reproduce, and diversify, creating a healthy rhizosphere. In return, they convert organic compounds in the soil into water-soluble nutrients that can be taken up by plant roots.

Four Signs of Calcium Deficiency in Plants

To keep up with its vital role in supporting garden health and productive growth, a steady flow of calcium is required from seeding to harvesting.

Calcium is an immobile nutrient. Once it's absorbed by plants, it rapidly integrates into cell walls. Unlike mobile nutrients (such as nitrogen and phosphorus), which can be stored and transported from older leaves to younger ones, calcium is fully absorbed. It won't jump to different parts of the plant.

Therefore, the initial signs of calcium deficiency are localized – affecting only specific parts of the plant – and it primarily occurs on young leaves and new growth.

These are the most common manifestations of calcium deficiency:

Leaf Tip Burn

Leaf tip burning on tender leaves is one of the earliest signs that your plant has received some, but not enough, calcium.

Older and more mature growth looks lush and healthy, but the newest leaves are marred by black or brown lesions at the leaf tips.

As calcium deficiency progresses, necrosis will spread along the leaf margins and edges and reach the terminal buds and root tips.

Abnormal Leaves

Calcium deficiency also manifests as twisted, irregular, and all-around peculiar growth.

New leaves may appear with cupped, curled, or wrinkled edges. Leaves may be smaller than usual, twisted, or distorted, with leaf tips hooking backward.

Since calcium is involved in creating sturdy cell walls, as leaves unfurl, the new growth may stick together and tear.

Stunted Growth

As a builder of plant structure, calcium does benefit a plant's physical form. However, without calcium to aid in cell elongation and division, plants are typically much smaller and less productive.

Calcium-deficient plants are shorter, have fewer stems and growing points, and overall have fewer leaves. Stems may be brittle and prone to breakage. The root system may also develop poorly, with shortened root tips and limited root hairs. In some crops, it can lead to premature sprouting and flowering.

Blossom End Rot

One of the most overt signs that there is indeed a calcium issue in the garden is blossom end rot.

Blossom end rot begins as dark, watery spots at the bottom of fruit, opposite the stem. As the disease progresses, the soft spot dries and becomes a hard, black lesion that can consume over half of the fruit.

It primarily affects tomatoes, peppers, eggplants, zucchinis, pumpkins, watermelons, cantaloupes, and cucumbers. It first appears in fruit that is still immature but in rapid growth stages.

This occurs when there isn't enough calcium to create a firm skin and flesh for the fruit. The fruit's cell walls and membranes lose integrity and can't hold the skin together, resulting in internal leakage. The wet spots eventually dehydrate, creating a significant dead area at the lower part of the fruit.

How to Address Calcium Deficiency

While calcium deficiency is rare in nature, our densely planted garden plots can sometimes be affected by low calcium levels. This is especially noticeable when growing calcium-rich crops like tomatoes, peppers, and watermelons.

The quickest way to correct low calcium levels in the soil is to amend your beds with a calcium-rich granular supplement, such as:

Lime is an excellent source of calcium in the form of calcium carbonate and has a relatively direct impact on calcium-deficient plants. However, it's a highly alkaline substance that can raise the soil's pH. It's highly recommended to test the soil pH before and after applying lime in your garden.

Bone meal contributes calcium to the soil a bit more slowly than lime, but it doesn't affect the pH. In addition to calcium, bone meal contains a significant amount of phosphorus and a small amount of nitrogen.

Gypsum (also known as calcium sulfate) is a good fast-acting choice. It's one of the safest soil amendments to add as it is neutral and won't affect the pH.

Wood ash is a free source of calcium, potassium, phosphorus, and magnesium. It's also highly alkaline, so it's best used cautiously to avoid pH imbalances in the soil.

Over the long term, accumulate calcium levels in the soil gradually:

Add eggshells, animal bones, and other calcium sources to your active compost heap. This ensures that the finished compost will be rich in calcium once it's ready to use.

Sprinkle crushed eggshells around the base of your plants in the soil. However, it may take a considerable amount of time for the shells to break down into a form that's available to plants.

Mycorrhzal fungi is another gentle soil amendment that contains a lot of calcium, along with almost all other essential nutrients needed for plant growth.

If you've done everything correctly, but your plants still show symptoms, the cause might be environmental.

Calcium deficiency symptoms usually appear suddenly and aren't a result of low calcium levels in the soil but rather something that hinders the plant's ability to absorb it:

Acidic soil is one of the most common reasons for calcium becoming scarce. You can test soil pH using inexpensive test kits.

Overwatering and poor drainage limit the movement of oxygen and nutrients (including calcium). Improving drainage by amending beds with compost and sand can help.

Prolonged drought quickly stops calcium's flow, as water is necessary for the transport of calcium through plant tissues. Ensure your plants receive at least one inch of water per week, especially during dry spells.

Extended heatwaves and cold snaps put plants in survival mode, slowing growth and nutrient uptake. Protect your plants with shade cloth and row covers to mitigate temperature-related stress.

Nutrient imbalances can also hinder proper calcium uptake. Nitrogen, potassium, magnesium, and iron compete with calcium for root absorption. Overusing one or more of these competitors can lead to calcium deficiency. Flushing the soil with water can help leach out excess nutrients that may hinder calcium uptake.