When you see your plants struggling from slow growth, it could be a lack of calcium, and that means you need to know how to fix calcium deficiency in your plants. If you let this nutrient deficiency linger, your plants will quickly become stunted and weak.
Of course, calcium deficiency involves a lack of this nutrient in plants…but solving this issue isn’t as simple as adding more of this plant nutrient to your soil or solution. We’re going to cover the nuances involved in addressing this shortage and putting your plants back on track to vigorous growth and high yields.
What is Calcium’s Role in Plants?
Why does calcium even matter for plant health? After all, it’s not even a primary nutrient.
While plants don’t need as much calcium as they do nitrogen, phosphorus, and potassium, they require more calcium than they do micronutrients. Without enough of this vital nutrient, you’ll notice that plant growth is limited.
If your plants are suffering from a calcium deficiency, both structural and communicative functions will become interrupted.
Calcium is an essential component of both cell walls and cell membranes.
If a plant is lacking this nutrient, cell walls will be less rigid and you’ll notice it. New leaves and root tips will show unusual growth like discoloration and curling, and meristems may die back completely.
In cell membranes, calcium binds to phospholipids which increases stabilization. If a plant doesn’t have enough calcium, the permeability of the membrane rises which leads to necessary ions and compounds escaping cells.
Without calcium, plants have a hard time receiving messages regarding stressors and developmental processes. When plants lack calcium, you’ll notice a serious decline in their overall health.
Plants can often defend themselves when pests and diseases attack, but they must know they need to do so! Calcium is a crucial part of the chain that tells a plant it needs to protect itself. While this nutrient doesn’t directly fight against these enemies, it is a crucial component in the line of defense. If calcium is lacking, plants are more likely to experience serious damage.
Calcium also regulates the movement of other nutrients throughout a plant. While calcium is immobile, it helps tell the plant when mobile nutrients such as nitrogen, potassium, and iron are needed in certain tissues.
What Causes Calcium Deficiency?
You might be thinking calcium deficiency is caused by a lack of calcium. While this is true, it doesn’t tell the whole story. Just because there’s enough calcium in your soil or solution doesn’t mean your plants will have all the calcium they need. The following factors all have an influence on calcium deficiency.
The pH largely impacts the availability of calcium. If the pH of your soil or solution is below 6.0, plants will have a difficult time taking up this vital nutrient.
Calcium is a cation aka a positively charged ion. Its positive charge binds to negatively-charged sites on clay and organic matter particles.
You might have heard of the term cation exchange capacity or CEC. This refers to the ability of soil or other material to hold cations. Clay and organic matter have a high CEC while sand has a low CEC.
But, calcium isn’t the only element that binds to these sites.
Magnesium, sodium, potassium, aluminum, and manganese all bind to negatively charged sites, and an overabundance of one nutrient can lead to over-saturation. For example, if you apply ten times the amount of magnesium a plant needs, a large portion of exchange sites will be filled with this element. If you add calcium, it won’t have anything to hold it, so it may leach out of your soil or substrate.
If you need a refresher, transpiration is when water evaporates from plant tissue such as leaves and flowers. While plants take up lots of water through their roots, the vast majority of this water is cycled back into the atmosphere via transpiration.
How does this relate to calcium?
Calcium moves throughout a plant via the xylem, rather than the phloem. Remember that phloem are living cells that transport plant sap in multiple directions, while xylem are dead cells that transport water upward.
Since calcium can only move throughout a plant in the xylem, its movement is closely linked to transpiration rates. As water evaporates through plant tissue, suction action draws more water up through the plant.
Low transpiration rates are a common cause of calcium deficiency in plants since decreased evaporation leads to decreased movement of water — and calcium — through the xylem. Some common causes of low rates of transpiration include inadequate water, high humidity, and cold temperatures. This a probably a good time to read up on Vapor Pressure Deficit (VPD) to make sure you know how to keep your humidity balanced with your temperatures.
Calcium Deficiency Symptoms in Plants
Calcium is an immobile nutrient, so once it makes its way to a part of a plant it’s there to stay. If a new leaf forms and it needs calcium, older leaves can’t send any of this cation its way. That means that calcium deficiency symptoms occur in new growth before they show up in older plant tissue.
Symptoms vary between types of plants, but there are general themes across different species. If you spot any of the following symptoms, it’s likely that a calcium deficiency is to blame for your plant’s problems.
As a plant begins to lack calcium, new leaves start to curl at the edges. Another early sign of deficiency is yellow or brown spots on leaf edges. Eventually, the whole leaf will become dappled with these unpleasant spots. Careful, these can be mistaken for nutrient burn!
A lack of calcium also inhibits the growth of apical, or tip, tissue, so both shoot and root tips experience dieback. While you’ll be able to spot issues with the shoots, you would have to dig up the plant to see its roots. Since this is out of the question, know that root dieback can present itself as a general decline in plant vigor.Notice the brown apical meristem and curling leaves.
In fruiting crops, a lack of calcium can cause blossom end rot. This phenomenon is noted by a soft, rotting fruit tissue in crops including tomatoes, peppers, and melons.
A final symptom is a general lack of vigor. Since calcium is responsible for communication within the plant, low calcium means poor communication. And we all know that things take a turn for the worse when everyone isn’t on the same page. So if you notice your plant looks like it’s health is declining, it’s a good idea to check out calcium levels.
Do My Plants Have a Cal Mag Deficiency?
Sometimes you’ll hear growers say that they’re plants are lacking cal-mag, or calcium and magnesium. Since these nutrients are both cations, they are sometimes held by soil or media and left unavailable to plants.
While it is possible that plants are lacking in both of these nutrients, you can have a calicum deficiency but not a magnesium deficiency. In fact, this is a common occurrence!
The deficiency symptoms of these two elements can appear similar for someone who doesn’ know what they’re looking for. But the truth is that these nutrients exhibit quite different deficiency symptoms.
First off, magnesium is a mobile nutrient, so symptoms first occur in older tissue. As you learned above, calcium is immobile, so symptoms will show up in a young leaf before they do in an older leaf. While both nutrients affect the coloring of tissue, there are subtle differences. A lack of calcium creates spots of yellow and brown, while too little magnesium shows up as a yellow leaf with deep green veins.
Before you assume your plants are lacking both of these essential elements, carefully inspect them and apply only the nutrients they need. You can also submit a tissue sample for analysis if you’re unsure what nutrients your plant needs.
Sources Of Calcium For Plants
Learning about the many different calcium-containing products will help you learn how to fix calcium deficiency in plants.
Calcitic lime is largely composed of limestone high in calcium carbonate (CaCO₃). This material is often used to raise soil pH, as the carbonate reacts with hydrogen ions to neutralize the soil. Lime also adds calcium to the soil, but it’s important to take its effect on pH into account before applying.
Just like calcitic lime, this material contains calcium carbonate, but it also contains magnesium carbonate (MgCO₃). That means that this material raises pH and also supplies calcium and magnesium.
Also known as calcium sulfate, gypsum is a naturally occurring mineral that contains calcium and sulfur.
Bone meal is a fine powder made from crushed bones. It supplies plants with phosphorus and anywhere from 15-25% calcium, depending on the specific product.
Made from the shells of crabs and other crustaceans, this product supplies plants with nitrogen, phosphorus, and calcium. Depending on the brand, crab meal contains 10-20% calcium.
This is a chelated form of calcium that is water soluble. EDTA holds onto calcium molecules so they don’t leach out of solution or react with other elements to form compounds that are unavailable to plants.
Water Soluble Calcium for Plants
Different forms of calcium have varying levels of water solubility, and various factors impact the solubility for each product. For example, gypsum’s solubility is affected by water temperature, particle size, and soil properties.
How to Fix Stunted Growth Due to Calcium Deficiency in Plants
If your plants are exhibiting signs of calcium deficiency, don’t just dump more calcium onto them! It’s quite possible that your soil or solution has an adequate level of calcium but this nutrient isn’t making its way into your plants. In order to learn how to fix calcium deficiency in plants, you’ll need to learn the reasons why this nutrient might not be making it into your plants.
If you think there’s enough calcium in your soil or solution, but your plants are telling you that they need more of this essential nutrient, take a look at the following.
If plants don’t have access to water, they won’t have access to calcium. Drought stressed plants are often deficient in calcium, so make sure you’re providing enough water.
If your pH is too low, plants will not be able to take up calcium you add. If your pH is lower than 6.0, raise the pH before you attempt to fix any calcium deficiencies.
As we’ve said above, calcium in plants is linked to transpiration rates. If your grow room or outdoor garden is cold, transpiration rates will be low and a lack of calcium is likely.
Humidity and Airflow
High humidity and poor airflow can also lead to low transpiration rates. If you plants are sitting in humid and stagnant air, add in some fans to increase transpiration rates. Check your Vapor Pressure Deficit (VPD) level.
If all these factors seem in line with proper calcium uptake, you might need to add fertilizer to your soil or solution.
How to Put Calcium in Soil
Before you add any nutrients, including calcium, it’s wise to conduct a soil test. This will tell you how many nutrients are in your soil already as well as what to add.
If your soil is deficient in calcium, you can add this nutrient using various products. The product you choose largely depends on your soil pH.
If your pH is more than slightly acidic (with a pH below 6.0), it’s best to add calcium via lime, since this will raise the pH. If the soil pH is already at a desirable level, choose a product that doesn’t impact the pH, such as gypsum or bone meal.
When you add these products, be aware that they contain other nutrients! Before you apply a product to your soil, see if you’ll be creating an excess of some other nutrient.
How to Put Calcium in Solution
When you’re adding calcium to a nutrient solution, pay attention to the water you’re starting with. Hard water is high in dissolved minerals including calcium, so you won’t need to add as much calcium to hard water.
EDTA calcium, like Greenhouse Feeding Calcium, adds only calcium to solution, so you can add just the amount of calcium you need without over-applying other nutrients. This is also an extremely stable form of the nutrient, so there’s no need to worry about the calcium interacting with other nutrients or precipitating out of solution.
This form of calcium is also highly soluble, which means plants can easily absorb it. You don’t have to worry about applying calcium only to see it become unavailable to plants.
Just like with other nutrients, it’s helpful to use a nutrient feeding chart to calculate how much calcium you need to add during various stages of your plant’s growth cycle.
Now You Know How to Fix Calcium Deficiency in Plants
Now that you know all about calcium, you realize how important it is to fix any deficiencies! By optimizing environmental conditions and choosing soluble sources of calcium, you can help your plants recover from the adverse effects of a lack of this important nutrient.