How to Cure Nutrient Deficiency in Cannabis Plants

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Growing a successful crop takes hard work and dedication, but when you suspect your cannabis plants have a nutrient deficiency it means a mistake was made during the process. There is no real trick to yielding a strong crop, provide the right amount of light, the best climate, adequate water and the right level of nutrients and you should avoid any chance of a cannabis nutrient deficiency. Yet for many who grow their own plants, cannabis nutrient deficiency can be a common problem. Here we’ll look into cannabis nutrient deficiencies and how to cure those deficiencies.

How To Cure Nutrient Deficiency In Cannabis Plants

Mobile VS Immobile

When you start to notice your plants aren’t looking the way you’d like them to look it’s most likely that your marijuana has a nutrient deficiency. Marijuana nutrient deficiencies can be a challenge due to the fact that it can be hard to find what specific nutrient is missing. Many cannabis nutrient deficiencies will appear the same to an inexperienced grower which is why sometimes it’s best to try and flush out the soil with water before trying anything else. This is largely due to the fact that another nutrient which could be higher then it’s supposed to is blocking another nutrients from doing its job properly. For example if your plant has too much potassium it can prevent the plant from getting the right amount of iron. By flushing the soil, you can then test the pH level then add specifically what you think your plant is missing.

When trying to diagnose a weed nutrient deficiency you should know the different classifications of nutrients. Nutrients in cannabis plants are known as mobile or immobile, all depending if they can be moved from one place to another. A mobile nutrient shows deficiency at the base of the plant in older leaves, where an immobile nutrient will show signs of deficiency in the newly grown leaves at the top or the outer branches. Understanding which nutrients are mobile and which are immobile can help with the diagnoses for a cannabis nutrient deficiency.

pH Levels

pH Levels

So, how can you tell if your weed has a nutrient deficiency? One of the first symptoms you’ll notice if you have weed nutrient deficiencies will be the pH of the water and soil around and within the plant. When a plant absorbs nutrients it can only do so through its roots if the growth medium of hydroponic solution is at the right pH level. The pH scale is how growers can measure both the acidity and alkalinity of the soil and water around the plants. When gauging the appropriate amount of pH for your plant it should be ranged on a scale of 1-14, with 7 being the optimal number for neutral pH levels. On the scale, 1 is when your plant is extremely acidic where as 14 indicates the most basic level of alkaline. It’s important for the pH levels to be at a suitable level or damage will occur and the health of the plant will deteriorate.

How to adjust pH levels

This is a fairly straightforward process, all you need to do is either make the plant more alkaline or more acidic, depending where the pH level is sitting. Using a pH meter or testing strips from your local gardening store will help you keep your pH level regulated and will let you know if you are underfeeding or overfeeding your plants. Making sure the pH level is around 7 will make your plant absorb nutrients the fastest way possible. The easiest way to provide your plants with the right nutrients is through foliage feeding which is another term for making a tea and spraying the leaves of the plant.

Primary Nutrients – Macronutrients

Primary Nutrients – Macronutrients

There are many nutrients a cannabis plant needs to develop and grow into an acceptable crop, but if you think you are experiencing a nutrient deficiency problem, there are specific nutrients which you will want to investigate first. These nutrients provide a core that will help a plant grown and achieve a solid harvest, so it’s best to examine these nutrients first when dealing with possible weed nutrient deficiencies.


When dealing with weed nutrient deficiencies, nitrogen levels should be one of the first places you look. Nitrogen is an essential nutrient when it comes to plant growth and is heavily relied on when growing cannabis. Due to cannabis’s heavy use of nitrogen it is easy for your plant to develop a nitrogen deficiency and is why it is the most common marijuana nutrient deficiency. Nitrogen is very important during the life cycle of a cannabis plant and is vital during the vegetative growth. Nitrogen is used to help with such things as photosynthesis or the production of amino acids and chlorophyll.

When your plant has a lack of nitrogen the results will appear in the older leaves, the biggest indicator will be if the leaves begin to turn yellow and if unchecked they will wither and die. The yellowing won’t appear at the top of the plant but will appear towards the bottom, eventually spreading up throughout the leaves as time goes on. The flowering phase is when you could see the signs of nitrogen deficiency, during the flowering stage the plant requires an abundance of nitrogen which will be used up quickly during this phase. Without green leaves the plant cannot catch as much sun and produce energy so that it can continue to grow in a positive state, if the leaves remain yellow then the plant won’t have enough energy to grow and prosper. Plants can also have too much nitrogen, known as nitrogen toxicity. Indications of nitrogen toxicity are the curling of leaves, leaf stems becoming brittle, leaves turning dark green and flowering slowing down all together. Usually when nitrogen toxicity is the culprit, there is too much nitrogen in the plant which is being caused by a pH level issue, this is usually due to a pH imbalance rather then providing the plant with too much nitrogen.

When dealing with a marijuana nutrient deficiency such as the incorrect level of nitrogen it’s important to quickly find a solution because your plant needs nitrogen to survive. Certain supplies that can be found at your local gardening store can be used to help increase nitrogen levels:

  • Blood meal
  • Dried blood
  • Cottonseed meal
  • Bat guano
  • Fish meal
  • Worm castings

It’s also important to make sure you are using the correct fertilizer that contains appropriate ratios of macronutrients, such as nitrogen, phosphorus and potassium. As we stated before, during the vegetative stage of growth, plants require extra nitrogen, so don’t forget this during the growing process. If you do notice your leaves are turning yellow, just let them fall off, if you have replenished the nitrogen levels then new leaves will begin to grown back. When adding to the plant to help with the nitrogen levels make sure you are testing the pH level, as it could increase or decrease when you are treating the nutrient deficiency.


When dealing with a marijuana nutrient deficiency make sure your plant has an adequate amount of phosphorus, it is equally as important as nitrogen levels. It can be argued that phosphorus is the most important of the macronutrients during the flowering process, this is due to the fact that a lack of phosphorus during the flowering phase can limit the overall yield. Phosphorus is primarily responsible for your plant growing strong roots and increasing the strength of both stems and leaves. Having plenty of phosphorus is recommended as it is a necessity for your plants to go big and strong.

Symptoms of marijuana nutrient deficiencies usually show when the plant slows in growth and starts to look weak, this is especially true when your plant is not getting enough phosphorus. When plants are lacking in phosphorus the first stages of deficiency you’ll notice are darkening foliage and a slowing down of the plants growth. As the phosphorus deficiency continues other signs will begin to appear, the edge of the leaves will begin to lose their bright colours and start to curl in. When looking for a possible phosphorus cannabis nutrient deficiencies keep any eye out during the coldest days your plant is experiencing, during this period is when cannabis plants will struggle to absorb phosphorus from its soil. You will also notice it if you’re your soil is too wet or is rich in alkaline (pH levels).

When dealing with a weed nutrient deficiency of phosphorus it will usually always be during the colder temperatures. To help deal with the your weed nutrient deficiency it’s recommended that you buy both fertilizer and plant food which contains a higher level of phosphorus compared to what you had used before. Make sure the NPK ratio found on the package exceeds 5, this will directly help with your low phosphorus levels. There are also fertilizers that are specifically for the flowering stage which is when you will need the most phosphorus for your marijuana nutrient deficiency the most. It’s recommended that you use water soluble fertilizers as they are of the highest efficiency and simple to use. You can also use all purpose plant food like Miracle-gro, but make sure you only use half the recommended amount, if you use too much it could kill your plants. Last but not least you can use bone meal, worm castings, bat guano, crab shell and crab meal to help increase phosphorus levels. These are common solutions with growers as they have special abilities dealing with phosphorus deficiencies.


Another indicator of marijuana nutrient deficiencies is the common lack of potassium. Potassium is less required then other macronutrients when dealing with marijuana nutrient deficiency, the lack of nutrients usually comes from the fact that most fertilizers have a low ratio of potassium compared to phosphorus and nitrogen. Potassium like the other two main nutrients is vitally important to growing a successful yield, potassium’s main responsibility is water respiration, resistance of diseases, photosynthesis production and conversion processes and water circulation.

Potassium weed nutrient deficiencies can be a little more difficult to identify compared to phosphorus and nitrogen, some plants will continue to grow and will remain vibrant and strong but it’s the lower foliage you need to keep an eye on. One of the first indicators is when the leaves begin to turn brown or die, which will begin to slow the growth and development of the plant. When potassium is lacking the tell all will be in the leaves, they will begin to grow slowly and the tips might look burnt, existing leaves might start to look mottled and yellow, specifically between the veins. Like nitrogen and phosphorus, a lack of potassium can be very harmful on the flowering phase, leading to a bad final crop. Potassium is vital for transferring water and nutrients throughout the plant, so a weed nutrient deficiency of potassium can be very harmful for the health of the entire plant, not just one area.

Treating a marijuana nutrient deficiency for potassium is a relatively easy fix, marijuana plants absorb potassium with ease and at a fast pace. You can either add a fertilizer that contains more potassium or you can adjust your current fertilizer by adding a water-soluble potassium additive.

Secondary Nutrients

Secondary Nutrients

The macronutrients we listed above are most likely going to be the issues for a cannabis nutrient deficiency, but there are some more rare deficiencies that can occur that could effect your plants as well.


Sulphur is key in the organoleptic profile of flowers and is important to the chlorophyll production. Sulphur helps a plant produce and regulate its hormones and vitamins. When a plant is lacking in sulphur the plant growth can be delayed, leaves can start to distort before wilting and falling off. This can be solved using Epsom salts or a fertilizer that is rich in sulphur. If you have too much sulphur your leaves will turn dark green, this is rarely seen however as cannabis plants are very capable of managing too much sulphur.


Calcium helps with root development and helps with the nutritional balance which gives the plant control over certain nutritional excesses. When your plant has too little calcium the growth of the plant will be delayed around the roots. Leaves will begin to develop irregular margins and the tips will begin to curl. Lack of calcium can be easy to tackle with a calcium rich fertilizer. When you have too much calcium it can block the absorption of other elements such as potassium, magnesium and iron. To help with this just clean the roots thoroughly and feed the plant small amounts of a fertilizer containing all the micro and macronutrients necessary for proper plant development.


Magnesium is critical for chlorophyll production as well as photosynthesis. When you have a magnesium deficiency it is similar to having a lack of nitrogen, leaves begin to yellow and become distorted from the base to the tip. All you need to do is apply a fertilizer rich in magnesium and adjust the pH accordingly. When you have too much magnesium it can effect how the plant absorbs calcium, flush the substrate thoroughly and then use a fertilizer that contains the necessary nutrients.

Healthy Plants = Happy High

Dealing with cannabis nutrient deficiencies can be a trial and error process. You will know if you have solved your cannabis nutrient deficiencies when the yellowing and discoloration stops almost immediately. Some leaves might recover, so don’t get rid of any discolored leaves until you know exactly that the issue has been dealt with, if the problem hasn’t been dealt with then those leaves will continue to be effected and the issue is less likely to spread. Once you are fully confident you have dealt with the weed nutrient deficiencies then you can prune the damaged leaves lightly, so you don’t stress the plant anymore then it has been. Always pay close attention to your plants so you can identify any marijuana nutrient deficiencies as quickly as possible. Once you have dealt with the nutrient deficiencies give your plant a few days to recover before doing anything else. If you want to try and avoid cannabis nutrient deficiencies all together, make sure your seeds are very high quality as plants that posse strong genetics are less likely to having nutrient deficiencies.