Calcium Deficiency in Cannabis | Growers Choice Seeds

Calcium Deficiency in Cannabis

Calcium Deficiency in Cannabis Plants: Signs, Symptoms, and Solutions

Growing cannabis plants means paying attention to specific nutrient levels. When you give your marijuana the right levels of nutrients, you’re much more likely to have happy plants and a successful harvest. Calcium is one of the most important nutrients for cannabis plants, and making sure they have enough of it is essential during the growth cycle.

So, what happens when your plants experience calcium deficiency, then?

Calcium deficiency in cannabis can be common, but it’s easy to mitigate and avoid in the future. Here are the main signs, symptoms, and solutions for calcium deficiency in weed plants.

Why Calcium is Important to Cannabis Plants

This beneficial mineral plays several crucial roles in the cannabis plant, making it an essential component for healthy growth. One key role it plays is the help of the creation of cell walls: it assists in the development of strong, sturdy cell walls, which are necessary for the structural integrity of the plant.

Calcium also facilitates the uptake of other essential nutrients by the roots of the cannabis plant. It helps in the transport of nutrients through the plant, ensuring proper growth and development. The mineral also acts as an activator for several enzymes involved in various metabolic processes within the plant like photosynthesis, respiration, and hormone regulation.

Finally, calcium helps in regulating the pH of the growing medium you choose to use for your marijuana plants. It can neutralize acidic conditions which prevents pH imbalances that can hinder nutrient absorption and impact overall plant health.

Marijuana plant with yellowing leaves indicating nutrient deficiency
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Recognizing Calcium Deficiency

If your cannabis plant is not receiving enough calcium while growing, it’s going to suffer from calcium deficiency. This can present in a few different ways, and it’s important to understand the signs and symptoms, as well as the causes, so you can properly treat your plants—and ensure it doesn’t happen again.

Signs and Symptoms

Calcium deficiency in marijuana plants can manifest in a few different ways. You’ll want to look out for the following signs and symptoms to ensure your plants are getting the right levels of calcium while they’re growing:

  • Yellowing Leaves: One of the most common symptoms is that the leaves of the cannabis plant may begin yellowing, starting from the tips and progressing inward. This yellowing may eventually lead to necrotic spots on the affected plant tissue.
  • Curling Leaves: Curling of the leaves, particularly upward or downward, may occur in cases of calcium deficiency. This curling is often accompanied by the development of brown spots on the leaves themselves. You may notice this begin in the vegetative stage when the plants are forming their leaves.
  • Stunted Growth: Deficiency in cannabis plants can lead to overall stunted growth of the cannabis plant. This includes reduced stem elongation, smaller leaves, and slower development compared to healthy plants.
  • Weak Stems: Insufficient calcium may lead to weak and brittle stems that can’t support the weight of the plant properly. This weakness may lead to drooping or bending of stems, especially in the flowering stage when the plant becomes heavier with buds.
  • Leaf Deformation: Calcium deficiency may cause various leaf deformities, including cupping or the distortion of leaf shape. Cannabis leaves may look misshapen, wrinkled, or puckered in a sense.
  • Blossom End Rot: In advanced cases of calcium deficiency, cannabis plants may develop blossom end rot, particularly in the buds. This condition is characterized by dark, sunken lesions at the blossom end of the fruit or bud, leading to decay and reduced yield.

Causes of Calcium Deficiency

You know what to look out for when it comes to signs of calcium deficiency, but what actually causes this condition? There are a few different explanations.

One of the primary reasons for a lack of calcium is an improper pH level in the growing medium. Calcium uptake by the roots is hindered in acidic soils or hydroponic solutions with a pH that is too low, and in acidic conditions, calcium becomes less available for uptake by the plant roots, even if it is present in the soil or nutrient solution. Excessive application of certain fertilizers, particularly those high in potassium or magnesium, can also interfere with calcium uptake by the roots.

Soil compaction and poor soil structure can restrict root growth and limit the plant’s ability to access calcium in the soil, also leading to calcium deficiency. Along with this, overwatering or poor drainage can lead to waterlogged soil conditions, which inhibit root function and oxygen uptake. Finally, certain environmental stressors such as extreme temperatures, drought, or high humidity levels can impact calcium uptake within the plant. Sadly, stress can disrupt physiological processes and cause calcium deficiency in your precious weed plants.

Diagnosing and Treating Calcium Deficiency

While calcium deficiency in cannabis may sound a little scary, there are various ways to diagnose and treat it effectively.

Healthy cannabis leaf next to yellowing leaf next to dying curled cannabis leaf
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Before treating your plants for calcium deficiency, you want to make sure you’re diagnosing them correctly and it is, in fact, a nutrient imbalance. Doing this is going to involve careful observation of your plant’s growth and overall symptoms. Here’s how you can diagnose your cannabis plants with calcium deficiency:

  1. Visual Inspection: Examine the overall appearance of the cannabis plant. Look for any abnormal signs or symptoms on the leaves, stems, and buds.
  2. Symptom Identification: Identify specific symptoms commonly associated with calcium deficiency, such as leaf yellowing, leaf curling, stunted growth, weak stems, leaf deformation, or blossom end rot.
  3. Compare Symptoms with Reference Images: Use reference images or guides to compare the observed symptoms with those of known nutrient deficiencies, including calcium deficiency. This can help confirm whether the symptoms match those of calcium deficiency or if other factors may be causing the issues.
  4. Check pH: Test the pH of the soil or growing medium. Cannabis calcium deficiency is often linked to acidic soil conditions, so a pH below the ideal range for cannabis (typically 6.0 to 7.0) may mean potential calcium uptake issues.
  5. Assess Vital Nutrient Levels: If possible, test the nutrient levels in the soil or other growing medium to determine if calcium levels are within the appropriate range.
  6. Consider Environmental Factors: Evaluate environmental conditions such as temperature, humidity, and water quality, as these factors can influence nutrient uptake and plant health. Extreme temperatures, drought, overwatering, or poor drainage can exacerbate calcium deficiency symptoms.
  7. Rule Out Other Deficiencies or Problems: Consider other potential nutrient deficiencies or environmental stressors that may be causing similar symptoms. Compare the observed symptoms with those of other common nutrient deficiencies, such as magnesium, nitrogen, or potassium deficiency.


Now that you know how to properly diagnose your marijuana plants with calcium deficiency, let’s talk about treatment. There are a few ways you can approach this depending on the cause of your calcium deficiency, so first consider why it’s happening in the first place. For example, if the pH of the growing medium is too low, adjust it to the optimal range for cannabis cultivation, typically between 6.0 and 7.0. You can also try incorporating calcium-rich amendments into the soil or growing medium to provide a supplemental source of calcium.

Another good treatment option is choosing fertilizers that contain calcium as part of their nutrient formulation. Look for fertilizers labeled as “calcium-rich” or “high-calcium” and follow recommended application rates. Applying a foliar spray containing calcium directly to the leaves of the cannabis plant is also a great choice, as foliar sprays are absorbed quickly by the plant and can provide immediate relief for calcium deficiency symptoms.

Finally, if soil compaction and drainage issues are what’s causing the calcium deficiency, you can address these problems to promote healthy root growth and nutrient uptake. Incorporate organic matter into the soil to improve its structure and enhance nutrient retention, and ensure proper drainage to prevent waterlogging.

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Treating Your Cannabis Plants With Growers Choice Seeds

Growers Choice Seeds understands that treating your cannabis plants can be a bit complicated. After all, they are delicate and can be exposed to a lot of risks. However, when you buy high-quality cannabis seeds, you have a lot less to worry about from start to finish—and that’s exactly what we have to offer in our online seed bank.

At Growers Choice, you can choose from various cannabis strains available in either feminized photoperiod or autoflowering seeds. From classics like Blue Dream and Pineapple Express to newer options like Panama Red or Gelato strains, you’ve got so much to choose from. And, if you’re seeking hardy, disease-resistant seeds, we have plenty of those, too, with strains like White Widow and OG Kush.

Truly, no matter what you’re looking for next in your cannabis cultivation journey, Growers Choice seeds has the perfect feminized options for you.


How long does it take for plants to recover from calcium deficiency?

The recovery time for a marijuana plant that is experiencing calcium deficiency can vary depending on factors such as the severity of the deficiency, the plant’s growth stage, and how quickly you treat it. In mild cases, you may see improvements within a few days to a couple of weeks after addressing the deficiency through soil amendments, foliar sprays, or adjustments to nutrient management practices. However, severe cases may take longer to fully recover, potentially several weeks or more, as the plant needs time to absorb and utilize the supplemented calcium and repair damaged tissues.

What does calcium deficiency look like on cannabis?

Calcium deficiency in cannabis plants can look like the following:

  • Yellowing leaves, starting from the leaf tips and margins and progressing inward
  • Curling or distorted leaves, often accompanied by brown or bronze spots on leaves
  • Stunted growth, with smaller leaves and reduced overall plant size
  • Weak stems that may bend or droop under the weight of the plant
  • Leaf deformation, such as cupping or wrinkling
  • Blossom end rot in fruits or buds, characterized by dark, sunken lesions at the blossom end

What is a good source of calcium for cannabis?

There are several good sources of calcium for cannabis plants, including gypsum (or calcium sulfate), dolomite lime, limestone, and bone meal.

When is calcium deficiency most common in cannabis plants?

Calcium deficiency in cannabis plants can occur at any stage of growth, but it is more likely to occur during periods of rapid vegetative phase or during the flowering stage when the demand for nutrients is higher.

Regular monitoring of plant health and nutrient levels can help identify and address calcium deficiency promptly, regardless of the growth stage.

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