11 Common Cannabis Nutrient Deficiencies & How To Correct Them

In my over 2 decades of growing cannabis, I have battled (and beaten) every cannabis nutrient deficiency known to man. Back when I got started it was very difficult to diagnose and recognize the symptoms of many of the most common weed deficiencies because there was no Google or Reddit to turn to for help.

Today, the community has come together in an impressive fashion to help each other by sharing tips and solutions previously only available to a handful of expert growers.

At Organitek we want to do our part to help the community by sharing our guide to the 11 most common cannabis nutrient deficiencies, how to diagnose them, and how to correct them.

Cannabis Nutrient Deficiency Chart

Nitrogen deficiency (N)

Nitrogen deficiency is one of the more common deficiencies in cannabis and the symptoms are pretty easy to spot. Any dedicated cannabis grower should be able to tell whether his or her plants need more nitrogen fairly quickly.

• As chlorophyll disappears, the leaves cup (curl) upwards and they lose their vibrant color. They begin to look pale and yellow starting at the bottom of the plant and gradually moving upwards.

• Next the growth of the plant is stunted as flowers, branches, and leaves star to become dormant

• The leaves in the lower part of the plant may start dropping off. If the upper section of the plant also starts to turn pale, then you can be sure that it’s time for you to do something.

• Some of the worst cases of nitrogen deficiency in plants can be identified in the development of tiny purple spots on leaves, stems, and branches.

Learn How to Fix Nitrogen Deficiency

Yellowing signs of cannabis leaf deficiency

Phosphorus deficiency (P)

Identifying a phosphorus deficiency can be a little tricky, especially if you are a novice grower. You need to know the early symptoms and not get them mixed up with any other deficiency or issue.

The main symptoms of phosphorus deficiency include the following:

• Darkening of leaves – A phosphorus-deficient plant will exhibit dark green leaves, particularly on the lower and older parts of the plant. Yellowing leaves and brown spots (and in some cases dead spots) will start to appear and you may notice red or purple stems.

• Leaf curling & twisting – Leaves may curl downward, twist and become distorted in shape.

• Stunted growth – Plants suffering low levels of phosphorus have severely stunted growth and reduced vigor. Phosphorus is especially important during the flowering stage and a deficiency during this time will result in severely decreased yield.

• Poor root development - Phosphorus is needed in root development so a deficiency leads to an underdeveloped root system which in turn limits nutrient uptake and overall health.

Learn How to Fix Phosphorus Deficiency

Signs of Phosphorus weed plant deficiency

Potassium deficiency (K)

Recognizing the early signs and symptoms of potassium deficiency in cannabis plants is crucial for all growers so you can start treatment as quickly as possible. Some common potassium deficiency symptoms that you need to look out for are;

• Yellowing or browning of leaf edges – Potassium deficiency often begins with the yellowing or browning of leaf edges, especially on older leaves. This can progress to necrosis and leaf death, seen as brown spots on the leaves, if not addressed.
• Curling or twisting of leaves – Leaves may curl or twist inwards, eventually becoming necrotic and brittle.
• Weak stems – Potassium-deficient plants may exhibit weak, slender stems that are unable to support the plant’s weight.
• Slow growth and reduced yields – Potassium deficiency can negatively impact overall plant growth, resulting in reduced yields and poor bud development.

Learn How to Fix Potassium Deficiency

Cannabis leaf damage from potassium deficiency

Calcium (Ca) & Magnesium (Mg) deficiency

Calcium and Magnesium work together and is usually found as CalMag products. It’s fairly easy to diagnose a Cal Mag deficiency but you need to know how to spot the early symptoms in order to treat it quickly, effectively, and definitively. If left untreated or treated too late, a CalMag deficiency will cause all kinds of issues to everything from the roots to the flowers.

Calcium helps fortify cell walls which in turn helps your plants transport nutrients. Calcium deficiency results in weak stems, curled leaves, and overall poor plant stability.

Magnesium plays an important role in photosynthesis (the process by which plants produce energy from sunlight) by stabilizing the chlorophyll molecule. Magnesium deficiency results in yellow and lackluster leaves.

• The first signs of a CalMag deficiency can be spotted in the new growth coming from the plant. If new leaves show signs of yellowing between the leaf veins with brown spots, curling (or parachuting) of the leaf tips, and stunted growth, you should suspect a CalMag deficiency.

• After that, you will start seeing inter-veinal chlorosis on new leaves as the low magnesium levels inhibit photosynthesis and chlorophyll molecules break down. The low levels of calcium will lead to weak stems and poor root development making the entire plant lose structure and posture.

• Finally, the nutrient deficiency during the flowering stage will lead to poor bud development, less flowering, and rotting.

View our CalMag Nutrients

Learn How to Fix CalMag Deficiency

CalMag deficiency on weed plant

Zinc deficiency (Zn)

Nutrient deficiencies can be tricky because the early signs are usually similar between different deficiencies. Yellowing leaves and stunted growth is common among most of them.

But learning to recognize the small differences allows you to spot the early signs that indicate a zinc-specific deficiency. The three stages of a zinc deficiency and their common symptoms are the following:

The early stage of a zinc deficiency

• Inter-veinal chlorosis or inter-veinal yellowing (yellowing between the veins) on younger leaves

• Reduced leaf size where the new growth gets stunted and stops growing

• Leaf curling or distortion that is especially visible on the leaf edges

The progression of a zinc deficiency

• Necrosis (dead leaf tissue) browning on the tips and margins of leaves

• Stunted growth and reduced internode distance

• Delayed or abnormal flower development

The late stage of a zinc deficiency

• Severe leaf distortion and spreading necrosis

• Leaves start to turn completely yellow and brown and ultimately fall off the plant

• Widespread stunting and reduced yields with low potency and terpene production

Learn How to Fix Zinc Deficiency

Cannabis Zinc Deficiency as seen in the leaf

Iron deficiency (Fe)

Iron deficiencies come in 3 stages and the earlier you diagnose it, the sooner you can start to treat and correct it. Early detection is important because, in the later stages, the plant may be so damaged that it will affect the quality of the flower.

The Early Stage of an Iron Deficiency

• In the early stages of an Iron deficiency, your plants will start showing yellowing between the leaf veins, primarily on younger leaves and new growth. This symptom is known as inter-veinal chlorosis and it is easy to misdiagnose it because of its similarity to nitrogen deficiency but more pale and whitish in color.

The Progression of an Iron Deficiency

• As Iron deficiency progresses, the yellowing extends throughout the whole leaf, and the plant’s growth slows down. It’s very noticeable in the vegetative stage when you would expect explosive growth.

• Another telltale sign that your plants have lack of Iron is if the leaves start to turn white. In cases of severe Iron deficiency, it will almost look like the plant has seen a ghost.

The Late Stage of an Iron Deficiency

• In the late stages of Iron deficiency, leaves turn almost completely white or yellow and may show some browning at the tips. You will notice severely stunted growth and if left untreated, your plants will start losing leaves, and the yield will reduce drastically.

Learn How to Fix Iron Deficiency

Iron deficiency in cannabis plants

Copper deficiency (Cu)

Identifying a plant copper deficiency can be a bit tricky because it’s an uncommon occurrence but as the deficiency progresses, you will start to see color and leaf texture changes that are unique to a lack of Copper.

Here are the symptoms, progressing from the early to late stages of a Copper deficiency:

• In the early stage, you see changes in new growth as your plant’s leaves start taking on a peculiar bluish hue with purple undertones.

• The veins and petioles (leaf stems) start turning purple, and the leaf tips might twist or curl (similar to a Zinc deficiency). Newer growth may also start to exhibit a mild chlorosis or a yellowing.

• As the deficiency progresses, symptoms become more pronounced: yellowing will spread across the entire leaf, and spots of necrosis (tissue death) will start to appear as brown spots.

• You may notice your plant’s leaves curling upwards (a phenomenon often referred to as “cupping”), and the leaves feel stiff and look shiny.

• In the late stage, the areas of necrosis grow larger and darker, and the leaves become crispy to the touch. They eventually start to break, crumble, and fall off the plant as they die.

Learn How to Fix Copper Deficiency

Copper is an uncommon marijuana deficiency

Boron deficiency (B)

Even though Boron deficiencies are uncommon, they are not to be taken lightly. A lack of Boron can wreak havoc on your plants and significantly affect bud quality and yield. In the early stages, boron deficiency may seem relatively harmless, but as it progresses, symptoms worsen:

• The initial telltale sign is a subtle change in leaf color, usually to a lighter or yellowish hue (common to most deficiencies).

• You may notice yellowing along the edges of the young leaves accompanied by yellow or brown spots.

• Keep an eye out for deformed new growth such as twisted stems or curling leaves.

• As the deficiency progresses, symptoms will begin to affect older leaves as well.

• Growth tips and buds may begin to brown and die off.

• You need to touch the plant to see if the stems have started to become brittle and possibly even feel hollow or collapsed in areas.

• In the late stages, the growing tips may completely die off, causing substantial crop loss, and prolonged deficiency can lead to complete necrosis (plant tissue death).

Learn How to Fix Boron Deficiency

Manganese deficiency (Mn)

Detecting a Manganese deficiency can be very tricky because the symptoms are subtle and easy to misdiagnose. The main visible symptom is yellowing leaves and brown spots later on as the condition progresses.

Yellowing and brown spots are common to most cannabis nutrient deficiencies so at first sight, you will likely suspect another nutrient to be the culprit.

Manganese deficiencies are not very common so don’t jump to any conclusions before properly diagnosing the symptoms:

• In the early stages, the deficiency presents as slight discoloration, usually manifesting as yellow leaves due to decreased chlorophyll production.

• Unlike a Nitrogen deficiency where the entire leaf yellows uniformly, Manganese deficiency typically causes a mottled yellowing pattern of inter-veinal chlorosis (yellowing between the veins).

• The yellowing affects primarily young leaves towards the top of the plant.

• As the deficiency progresses, the yellowing of the leaves intensifies, but the leaf veins themselves remain green, which is a unique diagnostic sign.

• In the late stages, the yellow areas turn into brown necrotic spots (dead spots), and you will notice severely stunted growth.

• The leaves start to curl, wilt, and eventually fall off. At that point, there is usually no saving the plant, especially if this happens during the flowering stage.

Learn How to Fix Manganese Deficiency

Sulphur deficiency (S)

A lack of adequate Sulphur levels can result in yellowing of the leaves, stunted growth, and even woody stems that make the plant feel rigid and hard.

One of the primary causes of Sulphur deficiency is a lack of sulphur in the growing medium or nutrient solution because Sulphur in sandy soil has a tendency to bind to clay and organic matter, making it less readily available for root uptake.

Here are the symptoms, progressing from the early to late stages of a Sulphur deficiency:

• In the Early Stages, newer leaves will start turning yellow while the older, lower leaves remain green. (This is opposite to nitrogen deficiency.) Check the distance to the light source before concluding, as yellow top leaves are also common with light-burn. Sulphur deficiencies are quite uncommon.

• As the deficiency progresses, the yellowing spreads throughout the entire plant, fading from dark green to light green and later to yellow. You will notice that the plant’s growth slows down, and you sense a distinct lack of aroma.

• In the final stages, the underside of the leaves can turn a sickly reddish-purple or brown color. The plant starts developing woody stems and results in decreased yield. At this point, there is usually no saving the plant.

Learn How to Fix Sulphur Deficiency

Sulphur deficiencies on a cannabis plant may be devastating

Silica deficiency (Si)

You don’t normally see a deficiency in Silica but what you can experience is that Silica will work as a fantastic supplement for plants that are struggling with structure, pest, disease, and poor yield.

You will know that your plants need silica if you see the following symptoms:

• Weak stems

• Yellowing and stressed leaves with curling or wilting

• Increased susceptibility to pests and diseases

• Slow growth or reduced yields

Learn How to Fix Silica Deficiency

Consider that it may not be a deficiency…

If you are struggling with yellowing cannabis leaves you should always consider it a visible symptom of a bigger issue.

The problem is that, because yellow leaves are such a common symptom, you need to diagnose more than the leaf to understand what the underlying issue really is and it is not good practice to assume a cannabis deficiency.

There are 8 common reasons your weed leaves are turning yellow and we have a complete article on all 8 of them that you can read here.

• pH imbalance

• Temperature issues

• Light burns and leaf bleaching

• Under and overwatering

• Root rot

• Mite infestations

• Leaf Septoria

• Over/Under Fertilization