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Cannabis Deficiencies: the Ultimate Guide

Apr 7, 2021
Nutrient Problems

Cannabis Plant Deficiencies

As with all living organisms, cannabis plants need certain nutrients to thrive. Perhaps you’re seeing some slight discoloration of the leaves. Maybe you’ve noticed some light damage due to the leaves discoloring or contorting.


If you find that you’ve been making adjustments, but the condition doesn’t improve, the issue may lay within the soil. While the concept of nutrition may seem daunting to you, understanding your plants’ needs is a vital starting point on the road to an excellent harvest.


We’ll also have a look at a cannabis nutrient deficiency chart to help you identify potential symptoms at-a-glance.

What Are Cannabis Deficiencies?

Like human nutrition, where we have a food pyramid and specific daily requirements to stay healthy, plants have some essential building blocks. Some are paramount to their survival, where others improve the plant’s overall health and resilience. 


As you can imagine, a well-nourished plant will reward you with the best yield it can produce down the road.

Are Cannabis Deficiencies a Big Problem?

Whether you’re a casual grower, a seasoned botanist, or a large-scale farmer, you should consider the nutritional requirements of your cannabis plants for various reasons. Poor nutrition can make your plants more susceptible to pests and fungi, which could quickly spread through your crop and destroy an entire grow-room in no time. 


Cannabis deficiency burnt leaves

Only thriving, happy plants will produce the healthy fat cola we’re seeking. You can’t expect a malnourished plant to reward you with quality buds come harvest time.

What Nutrients Do Cannabis Plants Need?

Now that we’ve established that plants need all manner of marijuana nutrients to grow to their full potential while remaining disease-free, let’s look at these building blocks and their roles. 

What’s the Difference Between Macronutrients and Micronutrients?

Macronutes, micronutes, you’ve probably heard the terms being thrown around and responded with a nod and a smile, but we’re here to equip you to be a part of the conversation. Simply put, macronutrients are the essential requirements to prevent marijuana plant deficiencies. 


Micronutrients make up a considerably more extensive list of things that plants crave to grow prolifically, remain disease-free, and eventually produce a great crop of buds


Required in minute quantities, they can be thought of as multivitamin pills for plants. Plants can go for a while without certain micronutrients but can start suffering if deprived of them for too long.

Macronutrients from Air and Water

Plants obtain three nutrients from the water and the air: oxygen, hydrogen, and carbon.

Macronutrients from Soil

The “big three” which get absorbed through the soil are Nitrogen, Phosphorus, and Potassium. As a plant matures and goes into flower, the ratio of required nutrients changes.
Vegetative plants need more nitrogen and less potassium and phosphorus. 


Plants heading into bloom require far less nitrogen and significant amounts of potassium and phosphorus during this stage. 

The Optimum pH and Nutrient Levels

Besides providing the correct nutrients, monitoring and adjusting your soil’s pH is also of utmost importance. Marijuana plants prefer a pH of between 6.0 and 6.5. Anything that falls outside of this range will inhibit the roots from absorbing specific nutrients, known as a nutrient lockout. 


Some botanists routinely flush their soil to prevent this from occurring. More serious growers should consider investing in a pH meter and doing regular checks. There are also various products available that can adjust your pH up or down as required.

How to Identify Cannabis Deficiencies

Luckily for us, weed deficiencies tend to show on the plant’s leaves and are thus relatively easy to diagnose and treat if you spend enough time with your plants. In more advanced cases, you may see mold bugs or an unfamiliar residue. 


These are all signs that your plants may be lacking certain nutrients. Read on for our chart of common weed deficiencies and how to identify them.

Cannabis Deficiency Chart

This is so you can quickly diagnose and remedy the most common marijuana nutrient deficiencies. You’ll be able to diagnose many of the deficiencies by simply consulting a cannabis leaf chart.


cannabis leaf chart

If you’re growing in soil, it’s considered good practice to use larger containers of premium-grade compost. Giving the plant’s roots ample room to grow will allow it to draw nutrients from a larger surface area. 

Macronutrient Deficiencies

Let’s take a look at some of the essential nutrients required by cannabis plants to prevent stunted growth and even death. Understanding the difference between mobile nutrients and immobile nutrients will also help you diagnose your plants in the future. 


Mobile nutrients are those which the plant is capable of redirecting to different nodes as it sees fit. Common symptoms of mobile cannabis nutrient deficiency would be the yellowing of older, larger leaves while the new foliage may still appear perfectly healthy.


The nutrients that plants can’t transport around as required are called immobile nutrients. Marijuana plants suffering from these nutrient deficiencies are in more danger as they tend to affect the entire plant.

Nitrogen Deficiency 

Nitrogen is a mobile nutrient that’s vital during the vegetative stage. Common symptoms of Nitrogen deficiency in cannabis include:


Leaves will start to yellow, usually from the plant’s base, to the older and larger leaves first.


If left untreated, the yellowing will proceed up the plant eventually, causing leaves to turn brown and drop off. Ultimately, the plant’s growth becomes stunted, and you’ll see fewer bud sites with premature flowering and poor yields.

Phosphorus Deficiency

Phosphorus is another mobile nutrient that contributes to photosynthesis and carbohydrate release. Phosphorus deficiency isn’t a very common deficiency in soil, but it may be brought on by a pH level above 7.0. 


As with all macronutrients, a phosphorus deficiency in cannabis will harm a plant’s entire life cycle, from stunted growth to weak resin production. Signs of phosphorus deficiency include:


Older leaves and stems turning purple and eventually gaining a dark blue-green tint.


In advanced cases, growth will slow tremendously while dark purple or copper-colored spots begin to appear on leaves before they start to curl and drop. Depending on the strain, you may see a metallic purple or dark bronze hue on the leaves.

Potassium Deficiency

The mobile nutrient potassium is responsible for the manufacture and transportation of sugars and carbs. It’s also the primary agent in the process of cell division, water movement through the plant, and root growth.


Your plant simply can’t grow without potassium, and a shortage of it may even lead to your plant overheating and dehydrating itself by evaporating too much moisture through its leaves. Look out for these warning signs:


Leaves appear overly green, with the tips seeming burnt or almost rusty. Yellowing and brown spots are also common, especially on more mature leaves closer to the plant’s base.


Dehydration, curling leaves, and more apparently burnt leaves indicate more advanced cases. Plants lacking potassium will soon weaken and become more susceptible to pests and other illnesses. You may also expect a heavy decrease in the flowering of weed that has a potassium deficiency.

Can Your Plants Have Oxygen, Hydrogen, or Carbon Deficiencies?

These three elements make up the very framework of a plant, and a deficiency in one of them will have a swift and negative impact on its overall health. Oxygen gets absorbed through the rootst, and thus, the importance of good quality and well-aerated soil comes to light.


Plants absorb carbon from the air, most commonly from Co2, converted into carbon-containing sugars. This process is the first step of photosynthesis and requires that the plants receive ample light, especially in their vegetative stages. 


Hydrogen is most easily absorbed through plants’ roots in water, bringing us back to the importance of a healthy root system in soil of an appropriate pH range. As is the case with oxygen for us humans, a shortage in any one of these three elements will undoubtedly lead to the rapid decline and, eventually, the death of most cannabis plants.

Marijuana Micronutrient Deficiencies 

Once your plant’s primary needs are met, you should look at some of the nutrients you need to provide to make it go from ‘meh’ to amazing. 


Just like any consumable, you want to know that the cannabis product you intend to ingest is of the best quality attainable. Micronutrients pave the way to high THC and CBD levels, and a plant could mother many clones down the line.

Boron Deficiency

Boron is an immobile nutrient that partners with calcium to promote cell division, and just as with our bones, it grants stability to the plants’ cell walls. Your ladies need boron if you’re noticing slower leaf growth, yellowed or discolored sugar leaves, and wilting. 


You’ll also see a twisting of new growth and meristems that don’t seem to be going anywhere in cannabis affected by a boron deficiency.

Iron Deficiency

The immobile nutrient iron is responsible for chlorophyll formation, and the bright yellowing of new foliage usually indicates its deficiency. Iron is also responsible for much of a plant’s pigment production and is also essential in specific enzymatic processes. 


A cannabis plant suffering from an iron deficiency will quickly reflect this in the plant’s coloration. 

Calcium Deficiency

As mentioned before, this immobile friend to boron is what makes your plant stand upright. A shortage is often indicated by new growth forming incorrectly and becoming warped or bent. Overall, your plant may begin drooping and looking sad in general as a result of calcium deficiency in weed.

Magnesium Deficiency

Mobile magnesium is a primary component in chlorophyll, so plants use a ton of it. It’s essential in absorbing light and aids in producing enzymes that create carbohydrates and sugars, which ultimately make buds.


A tough one to diagnose early on, cannabis won’t show signs of a magnesium deficiency until three to six weeks after it has begun. The areas between the veins of leaves will turn yellow, and it often accompanies rust-colored spots.


Left untreated, the whole plant will become affected by more prominent spots, followed by leaves curling and dropping. The entire plant may also begin to look weak, and leaves will start to droop as a side-effect of magnesium deficiency in weed.


If your plant is close to flowering, these symptoms may advance rapidly and lead to a diminished yield of buds come harvest time.

Molybdenum Deficiency

The only mobile micronutrient, molybdenum, is involved in the two enzymatic processes that convert nitrate to ammonium, and it gets used in tiny amounts. Molybdenum deficiencies in cannabis are rare and may be brought on by exposure to colder conditions.


The observable symptoms of molybdenum deficiency include yellowing of older leaves, sometimes accompanied by discoloration along the edges. Advanced cases will see leaves curl and twist before dying and dropping from the plant.

Manganese Deficiency

Another immobile nutrient, manganese, helps plants use nitrogen and iron in the chlorophyll production process and aids oxygen reduction in the plant. This deficiency is also quite rare and tends to be caused by high pH or Iron overdose.


Like most immobile cannabis nutrient deficiencies, new growth will show lighter colors between the veins and brown spots, which will travel down the plant if left untreated. Leaves that are green, aside from noticeable yellowing between the veins, are the most common indicator of manganese deficiency in cannabis.

Silicon Deficiency

Silicon is hugely abundant in outdoor soil and a staple for most professional potting mixes. For this reason, silicon deficiency is highly unlikely in most potted cannabis plants. 


Nonetheless, it’s essential for a plant’s cell structure, and a deficiency will lead to droopiness in general. Pests will also find it much easier to invade the weakened sidewalls and stems of the plant. These marijuana deficiencies don’t occur that often, so make sure you rule out all other, more likely causes first.

Sulfur Deficiency

Sulfur is semi-mobile and is responsible for your plants’ breathing as well as the breakdown of fatty acids. Your plants also need it to produce oils and terpenes. A sulfur deficiency is also most often caused by incorrect soil pH, which will inhibit the roots from absorbing this nutrient.


Symptoms of sulfur deficiency in cannabis include leaves turning a light lime green and slowed growth. If a sulfur deficiency is left untreated, leaf veins will turn yellow before drying and falling off. In advanced cases, flower production will be negatively affected, and buds may suffer from much lower potency.

Zinc Deficiency

Zinc is another immobile player in the production of sugar and protein. It also promotes healthy stem growth and aids the retention of chlorophyll. Zinc deficiency in cannabis is pretty common, particularly in dry climates and plants rooted in alkaline soil. Ultimately, high pH levels are again most often to blame.


Symptoms include young leaves showing pale areas between veins, discolored or “burnt” leaf tips, and brown spots. Usually, the most notable sign is that leaves will turn 90 degrees sideways.

Copper Deficiency

Here’s another reasonably rare cannabis deficiency. Copper aids oxygen reduction, the metabolism of carbohydrates, and the nitrogen fixation process. Plants only need a tiny amount of copper, and its deficiency is a rare occurrence.


Leaves wilting slowly, followed by new growth turning or contorting are early symptoms. Dead spots on the tips of leaves or even the entire plant wilting are sure signs of advanced copper deficiency in cannabis.

Solve Cannabis Deficiencies and Keep Your Crops Healthy

Cannabis plants are tremendously hardy in general. If you make a point of providing them with quality soil, ample light, water, and well-balanced nutrients, you’ll hardly ever have to worry about deficiencies. 


Cal-mag marijuana deficiencies

Likewise, if you observe some symptoms, be sure to utilize the cannabis deficiencies chart provided in diagnosing your plant’s nutrient needs. 


The good news is that nearly all cases are fixable if you act quickly but, keep in mind that it’s always better to prevent than to cure nutrient deficiencies in cannabis plants.


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