Problem Identifier / How to Fix Calcium Deficiency in Plants

How to Fix Calcium Deficiency in Plants

Calcium Deficiency Cannabis
Calcium deficiency in a cannabis plant.

Calcium is a critical nutrient because it helps with plant stress from numerous sources including heat. Calcium is a semi-mobile nutrient incapable of moving through the plant quickly. Once a leaf has been provided with calcium, it generally remains. Calcium is important for actively growing leaves. When there is a deficiency, there is generally a lack of magnesium as well.

How Does Calcium Deficiency Affect the Quality of Your Plant?

A calcium deficiency in plants usually affects the quality of new leaves or partially grown leaves and portions of the fan leaves receiving exposure to light. The deficiency will slow down the plant’s rate of growth. The most obvious signs the quality of the plant has been affected include:

  • Little brown spots
  • Crinkling
  • Leaves begin to die
  • Distorted or undersized new leaves
  • Dead spots
  • Green areas next to the brown spots
  • Mottling or spotting
  • Stunted plant growth
  • Curled tips

What Are the Symptoms of a Calcium Deficiency?

The most frequently seen symptoms include:

  • The stems are flimsy or weak and tend to crack extremely easily
  • Signs of decay within the stems
  • Hollow stems
  • The plant is unable to be healthy under heat
  • The development of flowers or buds is incomplete or slow
  • The roots have an under-developed or weak appearance
  • Root issues such as slimy root rot

When the plant has experienced a calcium deficiency for an extended period, deficiency symptoms are much more likely to be present. In severe calcium deficiencies, parts of roots may even die off or turn brown. Roots are more susceptible to root problems like slimy root rot.

Possible Confusion with Other Symptoms

  • A calcium deficiency in plants can be confused with other symptoms. The most common include:
  • Mottled brown spots resulting from a manganese or boron deficiency
  • Brown spots appearing on the middle or lower leaves due to fluctuations in pH levels
  • Upward pointing or curled leaves resulting from heat stress
  • Excess potassium often has the same symptoms as a calcium deficiency

What Causes a Calcium Deficiency?

Calcium Deficiency Cannabis
Calcium deficiency macro of leaf.

There is a wide range of issues resulting in a mild to severe calcium deficiency. If the growing medium is too acidic or less than 6.2 pH, the result is often calcium being locked out by the plant even when enough calcium is present. Other issues include:

  • Other nutrients can be locked out due to an excess of calcium
  • The plants are being fed with either reverse osmosis or filtered water
  • Plants grown in soil with no calcium supplementation
  • The pH level is too low
  • There is not enough calcium in the tap water for specific areas
  • Plants grown outdoors in acidic soil with a pH level under 6.2
  • Cannabis grown in coco coir or hydroponics without the supplementation of calcium

How to Fix a Calcium Deficiency in Plants

  • Make certain the pH level is correct for the specific growth medium
  • pH water should be used to flush the entire system
  • Use a calcium-magnesium supplement

One of the key reasons for a calcium deficiency in plants is the pH level at the roots is either too low or too high. When the pH level of the root zone is not correct, the plants are unable to absorb the necessary calcium at the root level. The most important step is testing the pH level for the specific growth medium. When the plant is grown in the soil, the roots need a pH level between 6.2 and 7.0.

If there is a calcium deficiency, the pH level should be as close to 7.0 as possible. This is because the roots can absorb calcium at a higher pH. If the level is not a minimum of 6.2, the roots will be unable to absorb much calcium. If hydro is used as the growth medium, the recommendation is keeping the pH level between 5.5 and 6.5. Once again, the higher levels are recommended for efficient calcium absorption.

Calcium Deficiency Apple
Calcium deficiency in an apple, which is very similar to the symptoms of a boron deficiency.

If you believe your plants are suffering from a calcium deficiency, use clean pH water for flushing the system. The idea is to remove any nutrient salts potentially impacting the calcium uptake, and to help with the restoration of the pH to the correct level. Deficiencies in calcium and magnesium often go hand in hand.

A calcium-magnesium supplement is often recommended. This type of supplement is effective when mixed with the soil or used in a grow room. It works slowly and will raise the calcium level during the next few months. The pH level of most supplements is 7.0. This ensures the soil remains at the right neutral pH level for optimum growth. In most instances, between six and seven teaspoons need to be added to each gallon of soil.

A good example is a grow room with five gallons of soil. Between 30 and 35 teaspoons of the supplement needs to be added to the soil. The supplement and soil need to be mixed thoroughly. The next step is a light watering using water with a pH of approximately 6.5. Once the soil has been watered, mix it as thoroughly as possible. Do not add more plants or check the pH level for one to two days.

If the plants are grown outside, there are supplements specifically created for outdoor plants. Make certain to follow the directions on the package.

How Long Does It Take for a Plant to Recover from a Calcium Deficiency?

The recovery is dependent on the severity and length of time the calcium deficiency has been present. Generally, the plant will recover well enough within about one week for new growth to begin.


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