If you’re looking for answers to your questions about cannabis nutrient deficiencies, you’ve come to the right place.
As an avid grower and forever cannabis cultivation student, I understand the challenges and frustrations of dealing with periodic nutrient deficiencies in your garden.
With this blog post, I want to help you get a better understanding of the causes and symptoms of cannabis nutrient deficiency and provide you with simple and effective solutions.
We’ll dive into topics like:
- The importance of understanding the nutrient needs of your cannabis plants
- The different types of nutrient deficiencies
- How to diagnose and fix those deficiencies
By the end of this article, you’ll be well-equipped to deal with nutrient deficiencies and keep your crop healthy and thriving.
Every grower wants to unlock the ‘secret’ to growing the best cannabis. Since every grow room or environment is set up differently and has different variables, it’s best to maximize the variables you can control and understand.
Your plants need proper temperature/humidity, enough light, airflow, and a balanced nutritional diet with all the necessary macro and micronutrients at the correct pH.
When your plant(s) are missing just one element of the above list, plants will experience stress. This makes them susceptible to disease, mold, pests, and other problems. All of this results in lower quality, lower producing harvests.
Understanding deficiencies and how to correct them is a skill that allows growers to improve plant health. In this article, you will learn more about the most basic nutrient deficiencies in cannabis and what you can do to fix them. Even more importantly, you will learn some useful tips to avoid these cannabis deficiencies in the first place.
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What are cannabis plant nutrient deficiencies?
A cannabis deficiency is seen when the cannabis plant is unable to access a key nutrient or mineral essential for healthy growth. Even if your plants have a relatively healthy diet/feed, the absence of a single essential nutrient can have profound effects. This can have a severe impact on yield and/or quality. In the worst cases, a cannabis deficiency can threaten the survival of your plant.
Fortunately for weed growers, the cannabis plant can communicate many of the common deficiencies and issues to us. That’s assuming we know what to look for and how to interpret the signs. Visual clues from the leaves and general plant appearance can convey helpful information to the experienced cultivator. Read on to find out more.
Nutrients and pH levels for cannabis
One of the surprising and frustrating features of cannabis growing is that your plants can have a nutrient deficiency even if you have provided a balanced feed. Just because you have ensured that your plant has all the required nourishment doesn’t mean it can be absorbed at the root level. For nutrient absorption to take place at the root level, the pH needs to be within a set range. If the growing medium becomes too acidic or too alkaline, then the nutrients can’t be absorbed.
Before identifying any cannabis deficiency, it’s important to check that your pH is in the right region. Those growing in soil (or similar mediums) should aim for a pH of around 5.8-6.8. Halfway between, at around pH 6.3, is thought to be ideal. Note that many soils (and soil-related) grow media should ‘self buffer’ and be naturally at the right pH. But it’s always worth checking. Hydroponic growers will often refer to nutrient manufacturers’ recommendations, but a pH of around 6 is not uncommon.
It is always wise to be aware of the natural pH of your local water. Remember that your water pH can vary; don’t assume it is always the same. At different times of the year, with different rainfall and treatment levels, pH can drift up and down slightly. Understanding the pH of your water source is a good starting point and something worth monitoring.
Cannabis deficiencies and water supply
Some local water sources can have naturally high levels of some minerals but may be low in others. This can make it tricky to use certain nutrient additives if you already have variable levels in your water supply.
That’s why some professional growers try to take the variables within the natural water supply out of the equation and use deionized water. This is water that has been specially filtered to remove any mineral ions. The result is pure water that is free from any mineral content. Some growers prefer to use fully deionized water as the starting point. However, this approach tends to be used by a small minority of serious growers. Most cannabis home growers tend to use tap water and find it generally works well enough.
Cannabis nutrient deficiencies: macronutrients and micronutrients
Macronutrients are those required in high quantities by your cannabis plants. The main macronutrients of cannabis are Nitrogen, Potassium, and Phosphorus. These are used in many primary biochemical processes during vegetative growth and bloom.
Micronutrients are minerals required in trace quantities to ensure that plant cellular biology can function well. Micronutrients include Copper, Silicon, Zinc, Sulphur, etc.
Mobile nutrients vs. immobile nutrients in cannabis deficiencies
Understanding the subtle differences between mobile and immobile nutrients can also help the grower understand cannabis deficiencies better. Mobile nutrients such as Phosphorus can be transferred from one part of the plant to another. If that Phosphorus were stored in an old fan leaf before being transferred to another part of the plant, you would first spot the deficiency in older growth.
Other minerals, such as Zinc, are immobile minerals. Once deposited by the plant, they are difficult to transfer around the plant. This means that you might initially notice deficiencies of immobile minerals in new growth.
Cannabis deficiencies and excesses chart
Cannabis Deficiency Chart – Cannabis Leaf Deficiency Chart – Cannabis Nutrient Deficiency Chart – Weed Deficiencies Chart – The images and information in this post are partly based on content from Jorge Cervantes. All rights reserved. Visit marijuanagrowing.com for more information.
As always with cannabis cultivation, problem prevention is far better than cure. One classic problem with mineral deficiencies is that they are misinterpreted and treated incorrectly, worsening the problem. Some of the cannabis deficiencies can look similar and may take an experienced eye to identify correctly.
One basic way for soil growers to avoid deficiencies is to lean towards larger containers of high-quality, professionally prepared soil. With larger quantities of soil, assuming the soil is correctly formulated, the cannabis roots have a larger volume of nutrients to draw from. This reduces the chance of later deficiencies.
To further complicate matters, plants can sometimes experience multiple deficiencies, especially if they are growing in a low-quality grow medium. Of course, if the pH is out of range, then ‘nutrient lockout’ can occur. This is where nutrients are available but unable to be absorbed.
How to identify and treat plant nutrient deficiency
If you are unfortunate enough to have a sick plant with deficiencies, it helps to get on top of the situation as quickly as possible. If a plant continues to suffer from deficiencies, it usually means a severely compromised harvest. In the worst-case scenario, your plant may not survive. When a plant is in good health, it is far more resistant to pests and diseases than a plant already compromised by poor health and poor nutrition.
Nitrogen deficiency in cannabis
Nitrogen (chemical symbol ‘N’) is regarded as a mobile macronutrient. Not only is Nitrogen an essential part of plant proteins, but it is also vital for the healthy functioning of photosynthesis, especially in vegetative growth.
Nitrogen deficiency can result in leaves looking pale and eventually turning yellow, curling, and dropping off. Leaves nearer the base of the plant can be first displayed. Yellowing can progress up the plant. Leaf discoloration/browning can occur. Bloom may seem faster, with lower yields and fewer bud points.
If Nitrogen levels are too high, leaves can show an unnaturally deep/dark hue. This can be fixed with a decrease in nutrients or a quick flush of your plant container to remove the excess nutrients.
How to treat Nitrogen deficiency in cannabis
Many standard nutrients contain high levels of Nitrogen and are usually a quick fix. Fish-based nutrients are often rich in nitrogen-containing amines. Check that your nutrient pH is OK. Consider a light foliar feed spray with a nitrogen-rich nutrient, such as seaweed or fish-based foliar spray. Cannabis leaves can absorb small amounts of nutrients directly through the leaf surface. This makes foliar feeding a great option.
Phosphorus deficiency in cannabis
Just like Nitrogen, Phosphorus (chemical Symbol ‘P’) is a mobile macronutrient that is essential to plant health and growth. It is used in the formation of plant proteins and plant DNA and is essential for proper photosynthesis to occur.
If you have ever seen dry leaves with areas of brown discoloration then you may have seen Phosphorus deficiency yourself. It may also cause red/purple collations (or dead spots) in the petioles (leaf stems). The leaves may subsequently take on a dark blue/green hue. If left unchecked, P deficiency slows vertical and horizontal growth significantly. Dark, blackish spots can appear on leaves. Leaves can curl and drop, possibly showing hints of a metallic purple or a dark bronze
How to treat it
Keeping your pH nearer the acidic side (closer to pH 6) can help increase bio-availability. Adding a phosphorus-rich feed/fertilizer is recommended. Fish meal or worm castings are a good organic alternative. Ensure your temperatures are in range; cool temperatures seem to make it more difficult for effective Phosphorus uptake. Ensure you’re not over-watering.
How to prevent it
Try to use a growing medium rich in Phosphorus. To make the soil easier to grow in and use, use a well-aerated grow container such as an airport, which will allow better soil oxygenation levels. Perhaps some manure (well-rotted) in your compost will help. The use of beneficial mycorrhizal fungi will help with overall soil health. The microbes may also help convert less soluble phosphates into soluble forms, which are easier for your cannabis plant to absorb and utilize.
Potassium deficiency in cannabis
Alongside Phosphorus and Nitrogen, Potassium (chemical symbol is ‘K’) is the other main mobile macronutrient used by the cannabis plant. Potassium is vital for the synthesis and transportation of sugars and simple carbohydrates.
Potassium is also required to enable transpiration/water uptake as well as root growth and cell division. Potassium is also vital for the production of Adenosine Triphosphate (‘ATP’), which is a measure of cellular energy.
You may see curling leaves as well as brown and yellow colors on leaf tips and leaf edges. Your plants may stretch more than normal with a Potassium deficiency.
How to treat it
Some growers like to flush their grow medium to ensure they are not dealing with other issues, such as overfeeding, which can interfere with Potassium uptake. Chicken manure as a top dressing to your grow medium can help, as can a Potassium-rich nutrient or foliar feed. Organic seaweed is particularly useful as a foliar feed.
Magnesium deficiency in cannabis
Magnesium (chemical symbol ‘Mg’) is an immobile micronutrient. It is essential for photosynthesis and makes the vital chlorophyll pigment. Without Magnesium, chlorophyll and photosynthesis can’t happen.
As an immobile nutrient, any deficiencies tend to be seen in the new growth of leaves. The leaves start to show yellow spots, which eventually turn brown, causing the leaves to die. Areas between the veins of older leaves turn yellow (interveinal chlorosis) and may also show rust-colored spots. If left untreated, Magnesium deficiency can seriously diminish a plant’s ability to produce any harvest.
How to treat it
If pH exceeds the desired range, flush your grow medium with water (preferably at pH 6 or thereabouts). Epsom salts are often used to fix the problem. Try adding a teaspoon of Epsom salts to a liter of water and seeing how your plants respond to a feed. Some people benefit from water with naturally high levels of Magnesium. Try doing a Google search for water analysis where you live. In many countries, water analysis has to be legally available, showing you the precise levels of trace minerals that you can typically expect to be present. But remember, water composition and pH can vary at different times of the year.
How to prevent Magnesium deficiency
As with all cannabis deficiencies, prevention is better than cure. When you see the signs of a Magnesium deficiency, your plant may already have felt the effects for a month or so. Use good quality compost; large containers will contain more grow nutrients than small containers. You may wish to include some powdered dolomite limestone in your grow medium. This is Magnesium-rich and slowly breaks down, releasing Magnesium for the roots to uptake. Specialist Calcium/Magnesium-rich nutrients can also be bought in grow shops.
Calcium deficiency in cannabis
Calcium (chemical symbol ‘Ca’) is an immobile micronutrient, but one that has an essential role in the plant structure. Calcium helps fortify the cell walls. A Calcium deficiency can, therefore, result in warped structure/lack of structure to new growth. Calcium also helps the flow of Nitrogen and sugars through the plant.
Leaves, especially lower ones can curl and take on unusual shapes. You may also observe yellow/brown spots. These can have brown borders and will grow over time as the problem continues. Root health is also damaged by Calcium deficiency, root tips will slowly die. The result is a stunted plant that will struggle to recover in the worst cases. Don’t confuse a Calcium deficiency with environmental issues out of range VPD.
How to treat it
A Calcium/Magnesium nutrient supplement is a fast and direct solution. Ensure your feed pH hasn’t become too alkaline and is in range. If you don’t have a Ca/Mg supplement, you can try adding a teaspoon of hydrated lime to around 4 liters of water and using this as a feed. A good way to prevent Calcium deficiency (prevention is always better than cure) is to add powdered dolomite lime to your grow medium.
Boron deficiency in cannabis
Boron (chemical symbol ‘B’) is used together with Calcium to ensure healthy cell walls and effective cell division. Boron is an immobile macronutrient. It is required in small amounts, so it is one of the less common cannabis nutrient deficiencies to see. Most good quality soils/compost contain sufficient Boron.
A lack of Boron will produce a plant that looks like it’s wilting, the technical term is lack of turgor. Vegetative growth will be poor, new growth can appear twisted. The leaves can show a yellow/brownish discoloration.
How to treat it
Flush the grow medium and add some extra Boron. This is done by adding a teaspoon of Boric acid to 3-4 liters of water and feeding it to your plant.
Copper deficiency in cannabis
Copper (chemical symbol ‘Cu’) is a semi-mobile macronutrient. It helps the plant utilize Nitrogen and assists in the metabolism of carbohydrates. It’s unusual to see genuine cases of copper deficiency; most grow mediums and feeds have sufficient Copper for the plant requirements.
You will see slow wilting occurring. New growth can appear to twist and turn as it grows.
How to treat it
Treating deficiencies of mobile macronutrients such as Nitrogen, Phosphorus and Potassium are more straightforward than treating more complicated deficiencies involving micronutrients of heavier metals such as Molybdenum, Iron, and Copper, etc. Getting the correct dosing required, and the correct form of the mineral isn’t easy.
Who wants to be dosing their cannabis plants with heavy metals when they plan to be smoking the weed a few weeks later? Prevention of these deficiencies is the only real way to go.
Iron deficiency in cannabis
Iron (chemical symbol ‘Fe’) is a semi-mobile macronutrient. It is necessary for the use of nitrates (Nitrogen-containing) and sulfate (Sulphur-containing) compounds. Iron is also required for the production of chlorophyll. Iron deficiencies can occur if pH is out of range. Excess Zinc, Manganese, or Copper can also cause it. All of these can interfere with iron uptake. Iron is an important mineral for general metabolic and energy-forming processes.
Symptoms of Iron deficiency can initially appear in new plant growth. Interveinal chlorosis can appear at the base of new leaves. After this, the same symptoms can be seen through the leaves and older growth. Overall yellowing between the leaf veins is a good indicator of Iron deficiency.
Manganese deficiency in cannabis
Manganese (‘Mn’) is an immobile micronutrient. It helps with several important cell functions including nitrogen use, respiration, and photosynthesis. Root cell growth is aided by Manganese, which also protects roots from less useful/bad microbes. It’s unusual to see genuine cases of Manganese deficiency. Often it is related to excess Iron or high pH.
Just like other immobile nutrient deficiencies, Manganese deficiency tends to show up as pale discoloration (chlorosis) near the base of new plant growth. This can eventually spread out to affect the tips of leaves and brown (necrotic) spots start to appear, eventually on older leaves. The leaf margins and veins can appear green while the interveinal areas can start to yellow.
Molybdenum deficiency in cannabis
Molybdenum (chemical symbol ‘Mo’) is a mobile micronutrient. It is essential for the correct function of two important enzyme systems which convert nitrates to ammonium compounds (for the amino acid formation and subsequent plant protein production). Again, genuine deficiencies are rare and difficult to correct.
Genuine deficiencies are scarce, and they can be exacerbated by cold weather. You may see a yellowing of older leaves, which may also show interveinal chlorosis. The leaves may ‘cup’ and curl upwards before twisting and dying.
Silicon deficiency in cannabis
Silicon is an immobile micronutrient that has attracted much attention in recent years. Genuine cases of Silicon deficiency are uncommon. It’s a mineral that strengthens cellular walls, allowing sturdy growth and strong plants.
Specialist liquid Silicon feeds are available, though most growers use them in the hope of stronger plants rather than for trying to fix a deficiency.
Sulfur deficiency in cannabis
Sulfur (or Sulfur) is a critical immobile micronutrient. It’s used for vital enzymes and proteins. Sulfur is essential to plant respiration and the synthesis and breakdown of fatty acids. It also plays an important role in the synthesis of oils and terpenes. Deficiencies of Sulphur may be caused by the loss of phosphorus (due to a high pH level) in the root zone.
It’s uncommon to see a Sulfur deficiency, but if you have it you may see young leaves turning lime green before turning yellow. You may observe stunted growth followed by the gradual yellowing of leaf veins. The leaves may also be dry and brittle—continued deficiency results in lowered potency and inferior yields.
Zinc deficiency in cannabis
Zinc (chemical symbol Zn) is a metallic immobile micronutrient. It’s important for the production of sugar and protein. Zinc is also used to make chlorophyll and for healthy stem growth. Deficiencies can be seen, especially where alkaline soils and dry climates are present. It may also be the result of acidic pH levels. Zinc is only required in small quantities, but it is vital for forming cell membranes, proteins, and plant growth hormones.
The most common signs of zinc deficiencies are new leaves and new plant growth, which tend to show inter-veinal chlorosis. The blades of the cannabis leaf may look wrinkled, yellow, and distorted. The leaf tips will discolor (yellow) and may show a brown burn at the tips. The leaves may rotate 90º sideways.
Diagnosing common cannabis plant problems
The problem with emerging plant health issues is that they can be easily confused and misidentified. Many plant nutrient deficiencies, for example, involve the leaves yellowing in one way or another. Misdiagnosing the problem may well leave the problem unfixed – the plant continues to struggle, suffer stunted growth, and may even develop new issues due to the incorrect treatment provided.
Simply overwatering your plant and leaving it in a cold room may also result in yellowing/browning leaves. This could be misidentified as a deficiency of nutrients/minerals.
The experienced grower tends to avoid cannabis deficiencies by preparing for the grow with the right conditions, a consistent grow medium, and reliable nutrients.
If a grower frequently encounters nutrient deficiencies while growing cannabis in 5-liter soil containers, switching to larger grow containers of about 20 liters could help. Larger containers provide the cannabis roots with a greater reserve of nutrients, which allows them to develop a stronger root network and build a larger plant with a lower risk of deficiencies. Additionally, using slow-release organic nutrients can help replenish the soil health gradually. BioTabs is a highly recommended brand that offers excellent slow-release organic nutrients that can produce great results and prevent the risk of nutrient deficiencies.
Growers using hydroponic systems may find that refreshing their nutrient solutions more frequently reduces the risk of their tank running low on an important nutrient.
How to keep cannabis plants healthy – prevent nutrient deficiencies.
Successful cannabis growing requires mastering nutrient management, finding a consistent growing method/system, and understanding how your plant uptakes specific nutrients. Fortunately, growing cannabis is generally easy and versatile, as it can thrive in various growing mediums and systems.
Growing weeds can be done indoors, outdoors, or in a greenhouse. Using nutrients from established suppliers yields good results. Local grow shops provide qualified help. However, every cultivar consumes water and nutrients at a different rate, so slight nutrient deficiencies may still occur despite careful growing practices.
Original research and images by Dutch Passion.