Different Types of Cannabis Plant Nutrient Deficiencies

Different types of nutrients, signs of deficiencies, and what to consider next time you are feeding your garden.
11 May 2022
15 min read
Different Types of Cannabis Plant Nutrient Deficiencies

Contents:
  • 1. What causes a deficiency?
  • 1. a. The right ph for cannabis plants
  • 1. b. Ppm or ec ranges and measurement
  • 1. c. Using reverse osmosis water
  • 2. Mobile and immobile nutrients
  • 3. Nutrient lockout explained
  • 4. Deficiencies of primary nutrients
  • 4. a. Nitrogen
  • 4. b. Phosphorus
  • 4. c. Potassium
  • 5. Deficiencies of secondary nutrients
  • 5. a. Calcium
  • 5. b. Magnesium
  • 5. c. Trace elements explained
  • 6. What is the best way to avoid nutrient deficiencies?
  • 7. In conclusion

Growing cannabis is a lot of fun until your plants start dying without any rhyme or reason. Well, there certainly is a reason, but you don’t see it at that point of time. And, this can be very frustrating, especially if you’ve cared for the plants like they are your own children. Among the many problems ailing plants, cannabis nutrient deficiencies are the most common and can end up causing nutrient lockout.

A nutrient deficiency refers to any problem caused by the lack of macro or micronutrients caused by an improper pH or simply by underfeeding so It is important to supply your Cannabis plants with the perfect balance of primary and secondary nutrients, as well as trace elements. As plants mature and enter different stages of their lifecycle, knowing what to feed your plants, when to feed them and why they need that nutrient in the first place can be a huge difference-maker in the overall quality of your crop, including the health and vigor of your autoflowering cultivars. In this article, we explain the different types of nutrients, signs of deficiencies, and what to consider next time you are feeding your garden. 

1. What Causes A Deficiency?

Knowing that your plant has a nutrient deficiency is essential for maintaining a healthy crop because cannabis plants need nutrients to develop the branches, leaves and further along into their growth cycle, the buds. A nutrient deficiency occurs when your plants don’t get enough food, they become stressed and can be more susceptible to bugs, mold, and diseases which can reduce the yields and ultimately kill your plants.

 

Nutrient deficiencies: what causes it?

Cannabis fan leaf showing symptoms of deficiencies.
 

These nutrient deficiencies often present in the leaves, such as yellowing, burnt tips, and in more serious cases, crispy and burnt leaves so it’s essential you learn how to identify and treat them. But first of all, it’s important to know that a nutrient deficiency is not only caused by underfeeding but also due to improper pH levels and should not be confused with nutrient toxicity, which is caused by excessive feeding (aka overfeeding).

The Right pH For Cannabis Plants

So before checking your nutrient solution, it’s vital you check and adjust the pH because you may be feeding properly but a higher or lower pH won’t allow your plants to absorb the minerals even if they’re available in the medium. Cannabis plants can only absorb nutrients if the grow medium has the right pH, if the soil is too acidic (lower than 7) or alkaline (higher than 7), some nutrients won’t be available to the roots which can cause nutrient lockout, thus resulting in nutrient deficiencies. So before increasing the nutrient dose, make sure you test the pH of your water (if you’re feeding plain water) or nutrient solution, ideally, the pH levels should be between 6.0-7.0, but depending on the medium, they may change a bit.

 

Acceptable pH range for cannabis
MediumpH
Soil6.0-70
Hydro, aero, and soilless growing5.5-6.5

 

Have in mind that this is a general guideline and depending on the products you’re using and the medium of choice, the pH may differ, especially when using products designed for hydroponics. Once you’ve checked that the pH is correct, then it’s most likely you are looking at a nutrient deficiency which can sometimes lead to a nutrient lockout.

PPM or EC Ranges and Measurement

On top of measuring and controlling the pH range of any and all water that you supply to your crop, it is important to also know the amount of total dissolved salts (TDS). This is more important for growers using hydroponic or coco-coir mediums, as the nutrients are added directly into the feed water, but taking and understanding this measurement is also important for organic styles of cultivation. Measuring the TDS gives you an overview of the amount of organic and inorganic substances (which directly coincide with the number of nutrients) in a liquid. There are 2 different methods of taking this measurement, with either a TDS or EC pen.

Taking these measurements provides cannabis cultivators with an easy method of nutrient over or under-feeding diagnosis. To get a clear picture of how your plant is uptaking the nutrients provided, simply measure the water before you feed, and the runoff after the plant has had a chance at accessing said feed water. If your plant is healthy and uptaking the correct amount of nutrients the runoff reading should be lower than the original reading. In the case that the runoff and the feed water display similar readings, this is an indication that the crop may not be up to taking the provided nutrients correctly. This is usually caused by incorrect pH levels in the feed water or substrate and can be easily fixed by flushing the medium with correctly pH’d water and then refeeding. If there is no change in the results it might be best to leave the nutes out of the feed water for a day or two and then retest. 

If the runoff water reading is higher than the nutrient feed solution then you most likely have a salt buildup in the root system. If this is the case, head to your local hydro store and grab a bottle of enzymatic line cleaner. This wonder product helps with quickly and effectively stripping the root system of any salt build-up, and can be mixed directly into the feed water. If you can get your hands on enzymatic line cleaner, you can simply use filtered, pH-neutral water to help flush out the unwanted nutrients. This may take a couple of days wort of flushing to reach the intended levels.

Using Reverse Osmosis Water 

RO filtered water is a bit of a contentious subject, with opinions divided throughout the cannabis cultivation landscape. Some growers swear by it, with others of the opinion that it’s unnecessary and overly costly. But, in the case of nutrient deficiencies, it can make a huge difference in helping you diagnose and treat any issues that may pop up. RO water is passed through a semipermeable membrane filter which removes up to 99% of dissolved salts. This allows you to start from an almost totally inert baseline, which grants you much more control over what you do and do not feed your crop. It also removes the vast majority of bacteria, viruses, and any other microscopic nasties that may be floating around unseen in your local water supply.

While RO machines themselves can be prohibited expensive, you can purchase RO water online for decent enough prices. In general, we recommend grabbing some to have on hand should any nutrient deficiencies rear up throughout the grow, as RO offers a clean palette to help you flush and diagnose any and all nutrient and feed issues. We also recommend using coco-coir as your primary growing medium. This inert medium (nutrient-free, leaving the nutrient schedule totally up to you) offers many of the benefits of both soil and hydroponic cultivation methods in one and is super forgiving for new growers. It’s easy to maintain, easy to flush, and is pretty budget-friendly

2. Mobile and Immobile Nutrients

Nutrients are split and classified into 2 separate categories, mobile and immobile. This comes down to whether the plant can “move” the nutrients around once they have been assimilated, or whether they are locked close to the deposit location. This all sounds a little complicated, so let’s break it down to make it slightly easier to digest. Mobile nutrient deficiencies will usually show signs in the lower and older parts of the plants, usually in the bigger fan leaves at the bottom half. Immobile nutrient issues will present symptoms in the newer growth, in the upper half and the outer branches.

Mobile nutrients include:

  • Nitrogen (N) 
  • Phosphorous (P) 
  • Potassium (K) 
  • Magnesium (Mg) 
  • Molybdenum (Mo) 

Immobile nutrients include:

  • Sulfur (S) 
  • Calcium (Ca) 
  • Iron (Fe) 
  • Selenium (Se) 
  • Manganese (Mn) 
  • Boron (B) 
  • Zinc (Zn)

3. Nutrient Lockout Explained

Nutrient lockout sounds terrible but is actually a pretty simple concept that can be quickly resolved with the correct treatment. Time is of the essence though, as nutrient lockout can cause deficiencies very quickly, which can kill the plant in just a matter of days if the issue is serious enough. Nutrient lockout is the term we use to describe the situation where there are nutrients present and available to the plant in the root zone, but the plant itself is unable to uptake these nutrients. This can be caused by a range of issues:

  • Incorrect pH balance
  • Overfeeding
  • Underfeeding
  • Using low-quality synthetic fertilizers 

Nutrient lockout is an extremely common issue that cultivators face, especially novice growers. There is a tendency to think that more is better when it comes to feeding your crop, but that could not be further from the truth. In fact, many of the nutrient companies print the feeding instructions at the very upper range of what you should be actually feeding your crop; Remember, the more of these fertilizers we cultivators use, the more they sell. Makes great business sense on the nutrient producers’ part, but this can quickly lead to issues. If you are using unfamiliar synthetic nutes, it’s always best to halve the recommended dose to begin with and see how your crop reacts.

One of the main issues with a lockout is that it can be tricky to diagnose in the first place. Your plant may show signs that can point to multiple issues. The easiest way to tell if lockout may be causing the issues is to check the runoff of the feed water with a TDS or EC meter. If it comes out with a higher reading than the feed water, then lockout could be the problem. To remedy this, drop the humidity in your grow room to approx 50%, and flush the crop. To flush cannabis plants you want to start with pH balanced, filtered water if possible. Water the plants with about 3 times the usual feed amount, testing the TDS or EC each time you flush. The results should lower with each flush, but it may take multiple flushes over a day or two to actually get the salt levels to where they need to be.

4. Deficiencies of Primary Nutrients 

The primary nutrients (aka macronutrients) are the widely known Nitrogen (N), Phosphorus (P), and Potassium (K) which are needed in higher quantities. Due to absorbing a high amount of NPK, your plant can move these nutrients from one place to the other to solve a deficiency, this is why they’re also known as mobile nutrients.

 

Nutrient deficiencies: macronutrients

Symptoms of an NPK deficiency usually appear on the bottom leaves.
 

When facing a macronutrient deficiency, your plant will try to protect new plant growth by moving the nutrients from the bottom to the top, so if the leaves at the bottom are showing signs of deficiency, it’s usually a macronutrient deficiency.

Nitrogen 

Nitrogen is super important for cannabis plants due to being directly responsible for the plant tissue that makes green matter such as leaves and branches which are largely made out of nitrogen so a nitrogen deficiency usually stunts growth heavily. Despite the popular belief that nitrogen is only needed during the vegetative stage, but that’s not true because nitrogen is needed in order for your plants to photosynthesize and produce sugars to feed and grow, so even though it’s needed in smaller amounts, you should make sure it’s provided for your plants to grow healthy.

Signs of Nitrogen Deficiency

  • Fan leaves and surrounding foliage becomes a pale yellow color.
  • Tips and edges of the leaves curl up, at the same time losing vigor and shape.
  • Shortly after the yellowing, leaves begin to turn brown color, becoming dry, curl up and fall off naturally or with the slightest touch.

 

Cannabis nutrient deficiencies: nitrogen

If it’s not treated on time, the leaves become yellow and eventually start dropping from the plant.

How To Fix A Nitrogen Deficiency

  • Check and adjust the pH according to your growing medium.
  • Feed more nitrogen.

How To Prevent A Nitrogen Deficiency

  • Make sure you keep appropriate pH levels.
  • Maintain the growing environment in range according to the stage your plants are in.
  • Check the temperature of the nutrient solution if possible.

Phosphorus

Phosphorus is needed in lower mounts during the vegetative stage but it’s just as important as the other macronutrients due to being a part of the photosynthetic system. This element will not only result in bigger and denser flowers but it’s also responsible for helping transfer energy from the light to where the sugars are stored, this means that phosphorus is part of the energy usage system and will help move sugars to the areas where new growth is needed.

Signs of Phosphorus Deficiency

  • Brown spots appearing on the biggest leaves first. 
  • Leaves curl up, similar to the symptoms of heat stress.
  • Leaves look dry, dehydrated.

 

Cannabis nutrient deficiencies: phosphorus

Leaves and even stems turn purple. If left untreated, the purple color turns darker and even looks black at times.

How To Fix A Phosphorus Deficiency

  • Check the pH and adjust it if necessary.
  • Water with a phosphorus-rich fertilizer.

How To Prevent A Phosphorus Deficiency

  • Ensure the pH is within the acceptable range.
  • If possible, maintain ideal conditions for each stage of plant growth.
  • Make sure the nutrient solution is around 22-23°C.

Potassium

Potassium is also super important, just as important as the other macronutrients because it allows cannabis plants to acquire CO2 for photosynthesis, this happens because this element is pushed into the guard cells to open the stomata which are the tiny pores on cannabis leaves and is then pushed out of the guard cells to close the stomata during darkness. The stomata also control the transpiration process, so when there’s a lot of water they open to allow the water to evaporate, and when there’s limited water availability they close to avoid dehydration, so a potassium deficiency can lead to stress or can affect your plant’s basic processes and result in slower growth and reduced yields

Signs of Potassium Deficiency

  • Similar to a Phosphorus deficiency, signs of rusty brown spots will begin to appear on the surface of the leaves.
  • The leaf tips will begin to turn a pale yellow as more brown coloring begins to take over the rest of the leaf.
  • Over time the leaf will become crispy, curl up, and lose all life. 

 

Cannabis nutrient deficiencies: potassium

The leaves look dull and also burnt at times and will appear rusty and lifeless eventually.

How To Fix A Potassium Deficiency

  • Check the pH and adjust it accordingly.
  • Provide more potassium with a potassium-rich product.

How To Prevent A Potassium Deficiency

  • Check if the pH levels are within the acceptable range for the substrate you’re using.
  • Keep the humidity and temperature as close as possible to the ideal for each stage.
  • Ensure the nutrient solution is at room temperature.

5. Deficiencies of Secondary Nutrients 

The secondary nutrients (aka micronutrients) are the widely known Calcium (Ca), Magnesium (Mg), and some other less-known nutrients used in lower quantities such as Sulphur (S), Zinc (Zn), Copper (Cu), and Molybdenum (Mo) among others but despite being needed in lower quantities, they can also cause nutrient lockout.

 

Cannabis nutrient deficiencies: micronutrients

Micronutrient deficiencies usually appear on top growth due to being immobile nutrients.
 

Due to absorbing a lower amount of the elements cited above, your plant cannot move these nutrients from one place to the other to solve a deficiency, this is why they’re also known as immobile nutrients. When facing a micronutrient deficiency, your plant will not be able to move the nutrients around so if the leaves at the top are showing signs of deficiency, it’s usually a micronutrient deficiency.

Calcium 

Despite being a secondary nutrient, calcium is extremely important due to all of its functions such as energy and enzyme activity, aiding in cell division for growth and membrane structural integrity among others. Also, due to being a micronutrient, this element is immobile, meaning that your plant cannot move it to where it’s needed, making it essential for your to provide it from seed to harvest.

Signs of Calcium Deficiency

  • Leaves and stems will start to become very weak affecting the vigor.
  • Small brown metallic dots will appear on the fingers of the leaves and slowly become brittle and dry.
  • As the tips of leaves curl inwards, the leaf will become a dry, brown color.

 

Cannabis nutrient deficiencies: calcium

Early symptoms show brown spots on the leaves and as it progresses, you’ll see darker spots.

How To Fix A Calcium Deficiency

  • Make sure the pH is in the acceptable range.
  • Mix and feed a calcium-rich fertilizer as a soil drench.

How To Prevent A Calcium Deficiency

  • Check if the pH levels are between 6.0-7.0 for soil and 5.5-6.5 for hydro.
  • Check and adjust the environmental conditions if necessary.
  • Make sure the nutrient solution isn’t too hot or too cold.

Magnesium

Magnesium is very important for cannabis plants due to being an enzyme activator that plays a big role in harnessing light, this means that magnesium also plays a big role in producing chlorophyll and photosynthesis which results in better growth and better yields.

Signs of Magnesium Deficiency

  • Oldest growth will be affected first, meaning the lowest parts will be first to show symptoms, with the new growth being last.
  • Leaves will turn yellow, and there will be a strong contrast of the green veins on the leaf surface.
  • Once the leaf has turned yellow, the tips will turn a rusty brown, become dry, and curl upwards.

 

Cannabis nutrient deficiencies: magnesium

The veins of the leaves turn yellow from inside and spread to the outer areas of the leaves.

How To Fix A Magnesium Deficiency

  • Measure and adjust the pH according to your substrate.
  • Mix a magnesium-rich nutrient solution and feed your plants.

How To Prevent A Magnesium Deficiency

  • Make sure you read the manufacturer’s recommendations and keep pH within the specified range.
  • Keep ideal environmental conditions for each stage of plant growth.
  • Check that the nutrient solution is at room temperature, not too cold or hot.

Trace Elements Explained

Apart from the macronutrients and micronutrients, your cannabis plants also need trace elements: Trace elements are included in the micronutrient category but they’re used in lower amounts, the amount is so low that depending on your water source, you won’t even need to provide them because they’re naturally found in tap water, for example. But despite being used in lower amounts, failing to provide them will result in nutrient deficiency so make sure your plants are fed properly!

  • Sulfur

Sulfur deficiencies are quite rare, the signs of sulfur deficiency are thin, small, and fragile leaves, with sometimes yellowing of the leaves and slow growth.

  • Zinc 

Younger leaves will become affected first, with the tips becoming brown and curling upwards. As the leaves become yellow, there will be a strong presence of veins that become dark yellow.

  • Copper 

Responsible for the role of enzyme production for roots. The signs of deficiency in Copper are reddish and dark purple hues, usually something seen during the final flush.

 

Cannabis nutrient deficiencies: trace elements

Microelements are used in the smallest amounts by plants, in order to allow them to utilize all of the other available nutrients.
 

  • Manganese

Very important for the role of photosynthesis and used alongside Nitrogen. Spots will develop all over the surface of the leaf and may look similar to the rusty brown associated with Magnesium deficiency.

  • Iron

Another important element for the production of enzymes and aiding in chlorophyll production and photosynthesis. An iron deficiency will look almost identical to a Magnesium deficiency, so it is vital these two are not confused with one another.

  • Boron

Helping with the uptake of Calcium and is responsible for cell division. When there is a lack of Boron, new leaves will become stunted and slow growth. There will be a pale brown coloration to the inner part of the leaves.

 

Cannabis nutrient deficiency chart 
SulfurNew foliage turns lime green.Dry, brittle leaves.Weak flower production.
ZincLoss of normal green coloration.Thin leaves with burnt tips.Leaves turn sideways.
CopperWilted leaves.New leaves grow twisted.Dead spots on leaves.
ManganeseSymptoms start on new growth and gradually spreads.Green veins and yellowish leaves. Brown dead spots on leaves.
IronLoss of normal green coloration.Yellowing between the leave’s veins.Symptoms progress from top to bottom.
BoronBronze or brown spots on leaves.Yellow leaves.Twisted growth.

 

6. What Is The Best Way To Avoid Nutrient Deficiencies?

Nutrient deficiency in marijuana can be avoided by using organic nutrients but, first of all, it’s not obligatory to use organic nutrients but one of the many benefits of using them is that you avoid overfeeding, this happens because organic nutrients are designed to be broken down by the microorganisms in the soil, unlike synthetic nutrients which are fed directly to the roots. This allows your plant to “eat” when it needs and to absorbs the amount it needs to according to its stage, now, this doesn’t mean that organic nutrients are better but using slow-release powdered nutrients results in fewer chances of getting marijuana nutrient deficiency due to taking them taking some time to be broken down and be readily available.

 

Cannabis nutrient deficiencies: how to avoid

Organic nutrients can help you avoid deficiencies but it can be harder to fix them if they occur.
 

But this comes with a downside because organic nutrients may be more expensive and due to being released over time, you will have to brew an organic tea to deal with a deficiency if you’re dealing with a heavy feeder. If you don’t have access to organic products or just prefer synthetic fertilizers, make sure you measure the pH and ppm of your nutrient solution at every feeding, this way you guarantee that your plants grow big and healthy even with synthetic fertilizers or any kind of products you prefer or have available.

7. In Conclusion

Nutrient deficiency and nutrient lockout in cannabis are very common so providing autoflowering or photoperiodic Cannabis plants with the right amount of lighting, fresh air, and nutrients is a balancing act. Knowing what primary nutrients and trace elements your plants need is very important, as well as ensuring they have access to all the necessary elements. Organic growing mediums are created to fulfill all of Cannabis plants needs and avoid weed nutrient deficiency, however, hydroponics can be far less forgiving. Checking pH and E.C levels will also have an influence on the way nutrients are utilized by plants to avoid cannabis nutrient deficiency and nutrient lockout.

11 May 2022