How to Fix Calcium Deficiency in Cannabis Plants?

Just like our bones need calcium to stay strong and healthy, cannabis plants rely on this essential nutrient for their growth and resilience. While calcium may not steal the limelight (pun intended) like nitrogen, phosphorus, or potassium, it is critical in building stronger stems, aiding nutrient absorption, and even boosting pest resistance. 

Whether you're growing cannabis in soil, coco coir, or a hydroponic setup, ensuring your plants get enough calcium is non-negotiable for strong growth and maximum yields. In this article, learn all about calcium deficiency and how to fix it, sometimes by simply using tap water!

Why Is Calcium Important for Cannabis?

Calcium might not get the spotlight like nitrogen, phosphorus, or potassium, but it's still a vital nutrient for your cannabis plant's growth. As a secondary nutrient, calcium is needed in smaller amounts than macronutrients — but don't let that fool you. This mineral is essential at every stage of your plant's lifecycle.

Here's where calcium really comes in handy for your cannabis garden:

• Stronger Plants

Calcium is like a collection of steel beams in a skyscraper — it strengthens your plant's structure at the cellular level. A calcium-rich diet means stronger stems and leaves and a plant that can withstand external forces.

• Better Nutrient Absorption

Calcium helps your plant get the nutrients it needs. Without enough calcium, nutrient uptake slows down, leading to deficiencies that can cripple your plant's growth.

• Hormone and Enzyme Regulation

Calcium works behind the scenes to regulate your plant's hormones and enzymes. These processes directly impact how much energy your plant generates and how its traits (phenotypes) are expressed.

• Protects the Cells

Calcium acts as a bodyguard for plant cells, controlling what nutrients stay in and what gets kicked out. This balance keeps the cells functioning properly and ensures smooth operations throughout the plant.

• Pest Resistance

By strengthening your plant, calcium helps it stay resilient against external threats like pests and pathogens.

• Prevent Heat Stress

Calcium plays a big role in your plant's ability to handle environmental ups and downs, especially heat stress. It also improves healthy tissue respiration and stimulates protective enzymes.

Without enough calcium, your cannabis plants could face stunted growth, weak structures, and a slew of nutrient deficiencies. So, make sure your plant gets enough of it. Being a micronutrient, even small amounts of it can make a big difference for your plant. 

Is Calcium Mobile or Immobile?

Before we get to other things, it's important to understand how calcium is transported to other parts of the plant, which usually determines how the deficiency develops. While mobile nutrients can easily move from one part of the plant to another, immobile nutrients cannot do that. Therefore, this means that the young or new parts of the plant, including the shoots, leaves, and even roots must get calcium to survive. 

Implications of Calcium's Immobility:

• Because calcium is immobile from older to younger tissues, deficiency symptoms usually first appear in the younger leaves, new shoots, and root tips.
• To avoid calcium deficiency, ensure a steady and adequate supply of calcium from the growing medium, nutrient solution, or soil amendments. Make sure you have a set schedule for this since breaks in the availability of calcium, even for a short period, can permanently damage new growth.

How is Calcium Transported in the Plant?

If calcium is immobile, how is it transported from one part of the plant to another? Well, calcium moves through the plant's xylem when the plant takes in water. This process depends a lot on the plant's transpiration. 

This is how the process works.

1. Absorption by the Roots

Plant roots absorb calcium from soil or nutrient solutions as calcium ions. Root cells take in nutrients through passive diffusion or active transport mechanisms. Many conditions, including the pH of the soil, the concentration of the growing medium, and the competing ions affect the absorption ratio of calcium. 

2. Movement in the Xylem

After absorption, calcium is sent upward through the xylem. Incredibly, this movement is driven through transpiration — evaporation of water from the leaf surface — which pulls the water and dissolved nutrients available in the roots. Calcium travels through the water to stems, leaves, and other growing tissues.

3. Deposition in Plant Tissues

Calcium is deposited in areas of active growth such as young leaves, shoots, root tips, and cell walls. It plays an important role in the structure of cell walls as it is converted to calcium pectate which binds cell walls.

After being deposited, it becomes part of the physical structure of the plant and is not mobile any longer. Therefore, if a deficiency occurs later, it can't be sent to other places in the plant.

What Affects Calcium Transport?

• Transpiration Rate

When the transpiration rate is high, like in dry and warm situations, calcium movement improves. But when transpiration is low like in humid and poor airflow conditions, it can inhibit calcium movement. 

• Root Health

Roots that are infected or unhealthy may reduce the calcium uptake and movement to other parts of the plant. 

• Water Quality

When the water has a lot of dissolved salts or lacks proper nutrients, calcium absorption and transport are disrupted.

• Environmental Conditions

Transpiration and calcium movement to rapidly growing tissues like young leaves and buds are inhibited by stagnant air or low humidity.

What Causes Calcium Deficiency in Cannabis Plants?

Even if you're already using calcium-rich fertilizers or tap water, your cannabis plants might occasionally struggle with calcium deficiency — especially in hydroponic setups. But don't worry; spotting the problem early can save your grow.

Before looking at how to spot it, let's look at what causes it. Several factors can mess with your plant's calcium intake. Here are the usual suspects:

Even if you're already using calcium-rich fertilizers or tap water, your cannabis plants might occasionally struggle with calcium deficiency — especially in hydroponic setups. But don't worry; spotting the problem early can save your grow.

Before looking at how to spot it, let's look at what causes it. Several factors can mess with your plant's calcium intake. Here are the usual suspects:

1. pH Problems

If your soil's pH isn't in the correct range, calcium can get locked out, meaning your plant's roots can't absorb it. The availability of calcium depends a lot on the pH of your growing medium as it affects the solubility and the ability of the plants to absorb it as well. 

If your cannabis plants are growing in the soil, the pH should be between 6.0 and 7.0. If the pH becomes very acidic, it affects calcium availability. Conversely, an alkaline pH makes calcium bind with other minerals to form compounds that can't be absorbed easily by the roots.

If you're growing in hydroponics, the pH should be between 5.5 to 6.5 to ensure that the calcium dissolves easily and is then available to the plants. If the pH dips below 5.5, it causes calcium precipitation whereas a pH higher than 6.5 could cause deficiencies even if calcium is available in the solution.

It is very important to monitor and adjust the pH at a regular interval to avoid fluctuation in calcium uptake. For exact readings, a high-quality pH meter is essential. Growers can use pH Up or Down solutions to modify the pH value. Plus, buffering agents present in some nutrient solutions can help them remain stable over a long time.

If your pH issues are not corrected quickly, your plants may suffer from calcium deficiencies over a prolonged period. This can ultimately lead to weak plants and poor bud quality as well as more problems with pests and diseases. 

2. Poor Growing Medium Or Soil

A cannabis plant's growing medium is important as it determines the quality and availability of calcium in it. If your medium is deficient in nutrients and/or has a poor physical structure, it can severely restrict calcium uptake. Let's take a look at the types of soils to get a rough idea. 

• Sandy Soils

Sandy soils drain well but sometimes, it can leach through the soil even before the plants can access it. This problem is worse in areas that are regularly watered or receive rain. Improving sandy soils with organic matter such as compost or peat moss improves water and nutrient retention, creating a more stable environment for calcium availability.

• Compact or poorly aerated soils

On the other hand, compacted soils or growing mediums with poor aeration can impede root development and access to calcium. When the soil becomes dense, water will not enter the soil, which means there's a lack of oxygen and calcium may not move to the roots. Thus, a balanced soil structure and good aeration are very important and you need to take care of that. 

• Low-Nutrient Soils

Some soils are naturally low in calcium or other important nutrients because of their minerals. Soils that are heavily acidic or deficient often have low calcium levels. When you face this situation, you can add agricultural lime, gypsum, and dolomite to provide calcium back into the medium. More on this later. 

• Soilless Growing Media

Growers who use soilless systems, such as coco coir or peat-based mixes, can see calcium deficiency if the media is not pre-buffered or calcium is not supplemented. Calcium must be provided in forms that can be readily taken in by plants. In addition, there can be a problem if you choose containers that don't drain well, even if you're using soilless mediums that are very aerated. A good container is very important to minimize the risk of calcium deficiency

3. Nutrient Imbalances

Cannabis needs certain nutrients to thrive, but an excess of some can cause an imbalance that leads to calcium deficiency. This happens when the plant root takes up potassium (K), magnesium (Mg), and sodium (Na) like other cations that compete against calcium (Ca).

Typically, plants take in nutrients through root pathways which can be overloaded when a certain nutrient is in excess. For example, potassium is a common nutrient in soils and fertilizers that can prevent the uptake of calcium. This is because both potassium and calcium use the same uptake mechanism and plants prefer the uptake of potassium at the expense of calcium, which means that they can experience calcium deficiency easily. 

Cannabis requires magnesium for growth and flowering. However, high magnesium can interfere with calcium uptake since they both compete at the same absorption sites. 

In addition, there can be many other causes for nutrient imbalances. For example, using too much fertilizer or using it too often can add too much potassium or magnesium. Calcium lockout caused by high potassium levels can lead to nutrient deficiencies and toxicities that harm the plant.

Usually, other plants need a lot of fertilizers but cannabis has different fertilizing needs. Thus, when a product has too much potassium or magnesium compared to the calcium amount, it can create an imbalance in the nutrient supply available for the plant.

Finally, watering with a lot of dissolved salts, particularly sodium, can build up in the growing medium over time. Having a lot of these will cause competition for uptake which may lead to calcium and other deficiencies. 

If you're confused about whether your plant is suffering from nutrient imbalances, look for new shoots that look stunted. You may also notice dead spots on the leaves that curl and turn yellow. Also, the stalks may be weak and lack structural integrity. 

If you have added too many nutrients and suspect nutrient toxicity, first flush the medium with pH-balanced water to remove the excess nutrients. Next, switch to topsoil enriched with calcium, potassium, and magnesium or cannabis-specific fertilizers.

By knowing how nutrients can affect each other and avoiding an imbalance, you can ensure that cannabis plants get enough calcium for sturdy growth.

4. Water Quality Issues

When growing cannabis, it is important to pay attention to the quality of water we use and how it may affect nutrients such as calcium. Water that is high in dissolved salts, low in calcium, or not watered properly can affect calcium uptake and lead to deficiencies. 

For example, water with a high Electrical Conductivity (EC), can cause nutrient lockout. In this case, too many salts like sodium, magnesium, or sulfates compete with calcium for absorption. Over time, this leads to an imbalance wherein the calcium is made unavailable to the plant. In addition, sources of saline waters are also a frequent cause of deficiencies, particularly groundwater with salts or unfiltered well water.

There can be a problem even if the water contains less calcium: 

• Softened water often does not naturally contain calcium and magnesium. Water softeners use sodium, which usually exacerbates calcium deficiency in both soil and hydroponics.
• Distilled Water or Reverse Osmosis (RO) Water: This pure water has no impurities but it is also devoid of essential minerals like calcium. When using RO or distilled water, you must rely on nutrients that contain calcium to cover the shortfall.

But, what about water that's usually available everywhere? Yes, hard water is easily accessible and typically has calcium carbonate or other minerals that provide a natural calcium source for plants. But, if the water is very hard, it can cause lime and other residues in the growing medium, create an imbalance in the pH, and produce other nutrient issues.

Also, remember that the plant can have issues even if there's inefficient drainage as it can make the growing medium water-logged. Overwatering can lead to more problems as there will be less oxygen around the roots and since calcium is immobile, it cannot be delivered to growing tissues if there is poor drainage.

Similarly, if you underwater the plant, there can be a calcium deficiency. This is because calcium uses water as a medium to transport and when plants are not watered often enough, calcium becomes less available even though it is in the soil or nutrient solution To avoid this, you must water regularly and suitably so that calcium can move and be taken up by the plants. 

Here are a few ways to tackle water problems:

• Test your water regularly for pH, EC, and mineral content to catch potential problems. If water is lacking in calcium, then use calcium-rich amendments or calcium nitrate in the nutrient solution. 
• A reverse osmosis filter can eliminate excessive salts from a high-EC water source. But be sure to add back calcium and other essential minerals.
• Make sure your growing medium drains appropriately to prevent waterlogging, and water consistently to keep calcium mobile.

With good water quality management and calcium supplementation whenever necessary, you can avoid calcium deficiencies while promoting healthier cannabis plants.

How to Spot Calcium Deficiency in Cannabis Plants?

Calcium isn't a mobile nutrient, so your plant can't shuffle it around to fix deficiencies. This means the symptoms will show up in the new growth first. Keep an eye out for these telltale signs:

• Leaf Symptoms

• The young leaves may show irregular yellowing (chlorosis), as well as necrosis (brown or black) at the edges or tips.
• Leaf edges may bend upward, become dry, or get twisted.
• The leaves may dry and fall off in serious cases.

• Stem and Branch Symptoms

• Weak or thin stems that are subject to bending or breaking. 
• Overall stunted growth while new shoots became less vigorous.
• The distance between the nodes may become irregular.

• Bud Development Issues

During the flowering stage, the calcium deficiency can lead to buds that aren't formed properly and have fewer trichomes.

How to Add Calcium to Your Cannabis Soil?

Adding calcium to your cannabis grow doesn't have to be complicated. You won't need truckloads of the stuff, and the process is beginner-friendly. With modern techniques, you've got plenty of options to keep your plants thriving. 

Here are some effective ways to get started.

1. Use Calcium Fertilizers

The easiest way to give your plants a calcium boost is with a calcium-rich fertilizer. These fertilizers, available in organic and synthetic options, provide quick-acting nutrients that your plants can absorb without much fuss.

Here's the best part — they're super easy to use! Just follow the instructions on the label. But before you dive in, do a quick test of your soil's nutrient levels. This ensures you're not overloading the soil with something it doesn't need. 

2. Sprinkle Lime on the Soil

Lime — also known as calcium carbonate  — is another excellent option. No, we're not talking about the fruit! This mineral is affordable, easy to apply, and available in powdered form at most gardening stores. Simply sprinkle lime on the soil, ideally in the fall, so it has time to break down and work its magic. 

However, there's one catch: lime can raise your soil's pH. If the soil is already close to the ideal pH range for cannabis (6.0–7.0), adding lime might push it too high. So, grab a pH meter and check your levels before using it. If your pH is already in the sweet spot, it's better to skip the lime altogether.

3. Use Bone Meal

Bone meal is a powerhouse organic fertilizer for cannabis. Made from finely ground animal bones, it's rich in calcium and packed with nitrogen and phosphorus, giving it a well-rounded nutrient profile.

The beauty of bone meal lies in its longevity — it can provide a steady supply of calcium for up to four months. Add it to your soil at the start of the growing season, and it'll likely carry your plants through until harvest. 

However, like lime, bone meal can increase your soil's pH, so it's best used in slightly acidic soil or when you're okay with adjusting the pH occasionally.

You can find bone meal at most gardening stores. Just follow the recommended application rates on the packaging for the best results. Even if your plants aren't screaming for calcium, bone meal is a great addition to keep your cannabis garden thriving.

4. Or Dried Eggshells

Eggshells are another fantastic, budget-friendly option for boosting calcium in your cannabis garden. These everyday kitchen scraps are loaded with calcium; a little goes a long way.

To use eggshells, collect and dry them in a sealed container. Once dried, grind them into a fine powder using a food processor. The finer, the better — this helps them break down more efficiently in the soil.

There are two ways to apply eggshell powder:

1. Soil Amendment: Sprinkle the crushed eggshells directly into the soil and mix them in.
2. Soil Drench: Combine two tablespoons of eggshell powder with a gallon of water and pour it around the base of your plants.

Keep in mind that eggshells release calcium slowly, making them better suited for long-term than immediate fixes.

5. Try Gypsum 

Worried about messing up your soil's pH with lime or bone meal? Gypsum might be your new best friend. This naturally occurring substance releases calcium quickly and efficiently without altering your soil's pH balance.

Gypsum is widely available in gardening and horticultural stores, making it an accessible option in most places. It's especially handy if your soil already has a perfect pH range and you don't want to risk changing it.

6. Switch to Tap Water

If you've been relying on RO (reverse osmosis) or purified water, your calcium deficiency issue might be as simple as switching to good old tap water. Most tap water contains calcium naturally and could be just what your cannabis plants need.

Check your tap water's electrical conductivity (EC); an EC between 0.3 and 0.4 (or 150 to 200 PPM) usually indicates enough calcium to keep your plants healthy. Sometimes, the most straightforward solutions are the most effective. Make sure your local tap water is safe and free of harmful contaminants before switching.

How to Prevent Calcium Deficiency in Cannabis Plants?

As they say, prevention is always better than cure. If you're proactive, you can supply your plants with enough calcium throughout the whole growing cycle and prevent any damage. As you know already, calcium affects new growth, which means that it can be damaged if you don't take action. Ultimately, this affects the yields, so make sure you prevent calcium deficiency rather than trying to treat the plant later when it has spread. Here are a few tips to prevent calcium deficiency: 

1. Balanced Nutrient Regimen

If the nutrients are not properly balanced, or if some other factor competes with calcium, then there can be a calcium deficiency. Therefore, choose cannabis-specific fertilizers that contain the right balance of calcium and potassium as well as magnesium.

Also, make sure you don't use too many fertilizers. For example, you may like fertilizers from one brand but when you see another grower using nutrients from another brand, you may want to try that too. The same goes for adding way too many supplements. The plant will not be able to take in so much and can get overwhelmed. 

Too much potassium, magnesium, or sodium can block calcium. Stick to the recommended dose of fertilizers to avoid nutrient antagonism. In addition, remember to add calcium nitrate or chelated calcium to your nutrient mix when you are using soilless systems, hydroponics, or distilled/RO water to get enough calcium.

2. Regular Testing

Regularly check the soil pH and maintain it in the correct range. Whether you're growing in soil or hydroponics, you must check the pH and EC regularly to ensure that everything is working. Also, once you mix in the nutrients, wait for a while to let the pH settle and then check it. This means that you may have to wait for about half an hour or so. 

Once the plants start growing, check the pH before and after watering the plants. Unless you're growing cannabis organically where it's not necessary to constantly check the pH, the fate of your plants will depend on how proactive you are. Frankly speaking, this is one of the best ways to prevent calcium and other deficiencies. 

3. Choosing Calcium-Rich Amendments

Your growing medium can benefit from soil amendments and supplements to keep your calcium levels constant. We have named quite a few calcium-rich fertilizers, and you can use any of them regularly if you feel that your plants aren't getting enough calcium. 

Additional Preventative Tips

• Stringent irrigation practices should be followed. The quality of water should be suitable and balanced in calcium. If you're using distilled or reverse osmosis (RO) water, add calcium to the mix.
• Keep an eye on the moisture and heat levels. If they fluctuate too much, plants will get stressed, and this might mess with their feeding.
• Make sure to flush your growing media often to prevent buildup which may interfere with calcium absorption.

Calcium Deficiency in Hydroponic Systems

Calcium deficiency is rampant in hydroponic systems as the environment is controlled and the type of water you use plays a big role since it can limit the availability and absorption of calcium to a great extent. If you love growing cannabis plants in hydroponic systems, here are a few things you should keep in mind:

1. Limited Nutrient Availability

Calcium is less mobile than other nutrients, meaning that it cannot be moved readily around in hydroponic system plants. Thus, the deficiency symptoms commonly appear in new growth like leaves and tips first. It's like calcium deficiency in soil plants, only worse in hydroponics because there's no buffering medium like soil.

2. pH Fluctuations

Calcium will be optimally absorbed if the pH is maintained between 5.5 to 6.5. If the nutrient solution's pH drops below 5.5, then the calcium becomes insoluble and is not available to the crops. Having a pH that is above 6.5 will interfere with the efficiency of other nutrients, possibly causing the latter to become calcium deficient. In hydroponics, you should monitor and adjust the pH regularly.

3. Water Quality

Hydroponic systems tend to be more sensitive to water quality issues such as dissolved salts or poor water sources. Soft or distilled water, on the other hand, does not have enough calcium content and you need hard water with higher calcium content to help you. To have the best water quality and nutrient solution, the plants should have an adequate supply of calcium.

4. Nutrient Solution Concentration

You can easily change the concentration of nutrients in a hydroponics system, unlike a soil system, but be careful about sudden fluctuations. Too much potassium, magnesium, or sodium can block calcium absorption, which means you need to administer nutrients precisely so that a calcium deficiency doesn't occur due to antagonistic effects. 

Best Calcium Sources for Hydroponics

1. Calcium Nitrate 

The most popular calcium source in hydroponics is calcium nitrate. It supplies both calcium and nitrogen, aiding in vegetative growth effectively. Calcium nitrate is soluble in water, which makes it easily available to plants. Moreover, it ensures the efficient delivery of calcium. Calcium nitrate maintains the overall pH of the nutrient solution, making it a good fit to prevent either calcium deficiency or pH imbalance.

2. Calcium Chloride

Calcium chloride is a water-soluble source of calcium. It is often used along with other nutrients because it is quite salty. It can elevate calcium levels in the nutrient solution rapidly; however, it might slightly shift the pH level in the system, so you'll have to measure it frequently and stay on top of it. Calcium chloride is often recommended when you need calcium immediately. In addition, some growers shift from using calcium nitrate in the vegetative stage to using calcium chloride in the flowering stage to reduce nitrogen. 

3. Calcium Sulfate (Gypsum)

Gypsum may not dissolve in water as easily as calcium nitrate or calcium chloride. However, it can still find a place in hydroponics. It is particularly useful in systems where there is a need to stabilize pH. It contains calcium as well as sulfur and can be added to the growing medium as a slow-release product to provide a steady supply of calcium.

4. Calcium Carbonate (CaCO₃)

Calcium carbonate can also work in hydroponic systems but dissolves more slowly than others. It has other advantages such as being cheaper and allowing slow release and is often used in systems where you need the calcium to be released gradually to the plants. However, it does cause fluctuation of pH with time, so you'll need to monitor it frequently. 

Tips on avoiding and correcting calcium deficiency in hydroponic systems

• To avoid calcium deficiency, the pH of the nutrient solution should be maintained from 5.5 to 6.5. 
• Make sure to regularly test nutrient solutions for calcium levels and amend concentrations as required.
• Make sure the nutrient solution of calcium is well mixed and evenly distributed within the hydroponic system. This will help avoid calcium depletion areas.
• Calcium supplements like calcium nitrate or chelated calcium help to maintain appropriate levels of calcium in your nutrient solution.

Don't Give Your Plant Too Much Calcium, Though

While calcium is essential for cannabis plants, it's still unclear how much is too much. Most manufacturers suggest sticking to 150 to 300 PPM when adding calcium, whether through your growing medium or as a solution.

Remember, calcium doesn't play well with phosphates. If your nutrient solution contains phosphate, avoid mixing it with calcium directly, as it can cause reactions that might harm your plants. This is why calcium is often sold as a separate fertilizer — mix it fresh and apply it carefully to avoid any issues.

Summary: How to Fix Calcium Deficiency in Cannabis Plants?

Calcium might not be the most talked-about nutrient, but it's a cornerstone for healthy cannabis plants. From strengthening cell walls to aiding nutrient uptake, calcium ensures your plants grow strong, resilient, and productive. 

Whether you're using gypsum, bone meal, or even switching to tap water, there are plenty of practical ways to keep your cannabis garden calcium-rich. Remember to monitor your soil's pH and nutrient levels to prevent deficiencies or imbalances.