How To Prevent Cannabis Nutrient Deficiencies

Last Updated on May 20, 2021 by Kimberly Crawford

Growing cannabis is not a straightforward process. Besides learning how to dry weed, you also need to know what diet will be the best for your plants and how you can prevent them from getting damaged. One of the most common growing problems that many people face today is not providing their cannabis plants with enough nutrients.

If your plants struggle with nutrient deficiencies, it can negatively impact your yields, e.g., slow their growth. As such, you should always take a particular interest in what signals your cannabis plants give you. To make your job a little easier, we’ve created this article. Below, you will find two of the most common nutrient deficiencies and ways to prevent them. Let’s get started.

Magnesium Deficiency in Cannabis Plants

cannabis plants

Magnesium deficiency is one of the most common nutrient deficiencies in plants in general. It affects indoor and outdoor cannabis plants alike, regardless of whether they are grown hydroponically or in soil. This is because magnesium deficiency is often caused by over-fertilization or under-fertilization of other elements like nitrogen and phosphorus. Here is what you should know about it:


While magnesium deficiency in plants can appear in many forms, several are common if you have recently switched fertilizers or experienced growing problems with any element in particular (i.e., potassium). In cannabis plants, magnesium deficiency commonly manifests itself in yellowing leaves that eventually go brown and die off completely. Other signs include dark green spots on leaves and stems as well as leaf curling and overall stunted growth.

This is because magnesium is necessary for chlorophyll production as well as photosynthesis – the process by which plants convert light energy into chemical energy. As such, if your cannabis plant has a magnesium deficiency, you will notice that it will have trouble absorbing sunlight and producing new leaves and flowers.

Cannabis plants that experience magnesium deficiency also tend to produce significantly fewer buds than those with enough magnesium. In severe cases, plant growth can become so stunted that the plant does not have enough time to produce buds before dying off completely.


Many things can cause a magnesium deficiency in cannabis plants, including over-fertilization with calcium and potassium or overwatering your plant while using tap water instead of purified water. Poor soil drainage due to excessive clay can also cause magnesium deficiency in cannabis plants because magnesium is much less soluble in soil than it is in water.

When your soil drains slowly because of high clay content, the magnesium tied up within it takes a long time to reach your plant’s roots. As such, it is crucial to ensure that your soil drains well when growing marijuana both indoors and outdoors.

Other factors that can contribute to a magnesium deficiency in plants include:

  • poor nutrition
  • excessive heat
  • cold temperatures
  • excessive sunlight
  • overall lack of microbial activity within the soil that could cause root rot (anaerobic conditions)

A magnesium deficiency may also be caused by spraying your plants too often with water or fertilizer solutions; if you do this more than once per week, you run the risk of upsetting the magnesium balance in your soil and killing your cannabis plants entirely. For this reason, it is essential to avoid using excess fertilizer or water on your plants unless you need to do so for proper plant growth and yield.

Solution and Dosage

You can do many things to prevent a magnesium deficiency in cannabis plants, including avoiding tap water, ensuring your soil drains well, and using filtering or purified water for your plants. If you have a major problem with your water supply, you might want to consider using rainwater or distilled water instead.

To treat a magnesium deficiency in cannabis plants, you should first ensure that your soil drains well by adding plenty of organic matter to it and mixing it thoroughly. If the problem is due to nutrient imbalance, you should test your soil for pH and nutrient levels and adjust accordingly. You could also add a chelated magnesium fertilizer (100% water-soluble) to your solution if you want to make sure your plants get all the nutrients they need.

Calcium Deficiency in Cannabis Plants

canci cannabis plants

Calcium deficiency is one of the most common nutrient deficiencies in cannabis plants. It is a major problem for those who grow their marijuana plants indoors because it commonly occurs when cannabis grows directly in soil – even experienced growers occasionally run into problems with calcium deficiency in their indoor gardens. Here is what you need to know about it:


One of the most common symptoms of calcium deficiency in cannabis plants is stunted growth. This happens because calcium is an essential mineral for plant cell division and growth, allowing plants to produce new cells and grow larger. If your cannabis plant does not have enough calcium, it will not be able to divide its cells at an optimum rate, leading to slow growth and stunted development of new flowers and leaves.

Other signs of a calcium deficiency include:

  • white spots on leaves (often with yellow halos)
  • browning leaves
  • leaf curling
  • overall reduced plant health.


Calcium deficiency in cannabis plants is usually caused by overwatering your plants when growing them indoors. Excess water can leach away essential nutrients from the soil and prevent calcium from reaching your plant’s roots.

It can also occur if you use tap water for your plants since much of the calcium in tap water is tied up as calcium carbonate (which means that your plants have little access to it). If you use tap water, you should consider using a calcite supplement to prevent calcium deficiency in your plants.

Other factors that can contribute to a calcium deficiency in cannabis plants include:

  • an overabundance of potassium or sodium in the soil or fertilizer
  • anaerobic conditions
  • cold temperatures.

Solution and Dosage

A key way to prevent a calcium deficiency in cannabis plants is to test your soil for pH and nutrient levels before you begin growing. You should also ensure that you are using purified water for your plants instead of tap water if you plan on keeping them indoors for too long. Next, you should add a calcite supplement to your solution to ensure that the pH of your soil is balanced appropriately.

Remember that too much potassium or sodium will prevent your plants from absorbing calcium properly. For this reason, it is crucial to ensure that the balance of elements in your solution is appropriate before watering your plants.


Two primary nutrient deficiencies that occur in cannabis plants are magnesium and calcium deficiencies. Among the causes that may lead to them are overwatering and using tap water, over-fertilization of your plants with potassium or sodium, improper temperatures, and excessive sun exposure.

Fortunately, there are several ways to prevent nutrient deficiency in your cannabis plants. Ensure that the soil drains well, that you water them using purified or rainwater, and test its pH and nutrient levels regularly. Keep an eye on your plants, and they’ll reward you with the highest yields!