Understanding and Correcting Common Cannabis Nutrient Deficiencies

In my extensive experience of growing cannabis for nearly two decades, I’ve encountered and overcome various nutrient deficiencies that often plague these plants. In the earlier days, identifying and remedying these issues was a challenge due to the lack of online resources. But now, thanks to the collaborative efforts of the community, we can share valuable tips and solutions to help fellow growers.

At Organitek, we believe in supporting the cannabis community. To contribute our part, we have created this comprehensive guide to the most common nutrient deficiencies in cannabis, along with methods to diagnose and address them effectively.

Cannabis Nutrient Deficiency Chart

Silica

🟡 = Some symptoms
🟠 = Medium symptoms
🔴 = Severe symptoms

Nitrogen Deficiency (N)

Nitrogen deficiency is one of the more prevalent issues in cannabis plants, identifiable by distinct symptoms that keen growers can easily spot. Look out for the following signs:

1. As chlorophyll levels drop, leaves start to cup (curl) upwards, losing their vibrant color. They appear pale and yellow, starting from the lower part of the plant and gradually moving upward.
2. Stunted growth becomes evident as flowers, branches, and leaves enter a dormant state.
3. The lower leaves may start dropping off. If the upper section of the plant also turns pale, it’s a clear indication that action is needed.
4. In severe cases, tiny purple spots may appear on leaves, stems, and branches.

Learn how to fix Nitrogen deficiency.

Phosphorus Deficiency (P)

Identifying a phosphorus deficiency can be challenging, especially for novice growers. It’s essential to recognize the early symptoms and differentiate them from other deficiencies or issues. Look for the following main indicators:

• Darkening of leaves: Phosphorus-deficient plants exhibit dark green leaves, primarily on the lower and older parts. Yellowing, brown spots, and sometimes dead spots may appear, along with red or purple stems.
• Leaf curling and twisting: Leaves may curl downward, twist, and become distorted.
• Stunted growth: Phosphorus plays a crucial role in flowering, and its deficiency during this stage results in significantly reduced yield.
• Poor root development: Phosphorus is vital for root growth, so a deficiency hampers nutrient uptake and overall plant health.

Learn how to fix Phosphorus deficiency.

Potassium Deficiency (K)

Early detection of potassium deficiency is crucial for all growers. Look out for these common symptoms:

• Yellowing or browning of leaf edges: Potassium deficiency often starts with yellowing or browning of leaf edges, primarily on older leaves. If left unaddressed, necrosis and leaf death, visible as brown spots, may occur.
• Curling or twisting of leaves: Leaves may curl or twist inwards, eventually becoming necrotic and brittle.
• Weak stems: Potassium-deficient plants may have weak, slender stems incapable of supporting the plant’s weight.
• Slow growth and reduced yields: Potassium deficiency negatively affects overall plant growth, resulting in reduced yields and poor bud development.

Learn how to fix Potassium deficiency.

Calcium (Ca) & Magnesium (Mg) Deficiency

Calcium and Magnesium deficiencies often occur together and can be diagnosed by recognizing early symptoms. These deficiencies can significantly impact various aspects of plant growth, from roots to flowers.

• Calcium: Deficiency weakens cell walls, resulting in weak stems, curled leaves, and overall poor plant stability.
• Magnesium: Deficiency affects photosynthesis by destabilizing the chlorophyll molecule. Leaves turn yellow and lackluster.

Detect a CalMag deficiency through the following stages:

1. New growth: Look for yellowing between leaf veins, brown spots, and curling leaf tips, indicating a CalMag deficiency.
2. Interveinal chlorosis: Magnesium deficiency leads to yellowing between veins as chlorophyll molecules break down. Calcium deficiency causes weak stems and poor root development, compromising overall plant structure.
3. Flowering stage: Nutrient deficiency during this stage leads to poor bud development, reduced flowering, and potential rotting.

View our CalMag nutrients.
Learn how to fix CalMag deficiency.

Zinc Deficiency (Zn)

Identifying nutrient deficiencies can be challenging due to similar early signs. However, recognizing the unique symptoms of a zinc-specific deficiency is crucial. The following stages and common symptoms help identify a zinc deficiency:

Early Stage

1. Interveinal chlorosis: Younger leaves exhibit yellowing between the veins.
2. Reduced leaf size: New growth becomes stunted.
3. Leaf curling or distortion, particularly visible on leaf edges.

Progression

1. Necrosis browning: Tips and margins of leaves develop dead tissue.
2. Stunted growth and reduced internode distance.
3. Delayed or abnormal flower development.

Late Stage

1. Severe leaf distortion and spreading necrosis.
2. Leaves turn completely yellow and brown before falling off the plant.
3. Widespread stunting, reduced yields, low potency, and terpene production.

Learn how to fix Zinc deficiency.

Iron Deficiency (Fe)

Iron deficiencies progress through three stages, with early detection being crucial to prevent significant damage to plant quality.

Early Stage

In the initial stage, younger leaves and new growth show yellowing between the leaf veins. Similar to nitrogen deficiency, the color is paler and whiteish.

Progression

As the deficiency progresses, yellowing extends throughout the entire leaf, and plant growth slows. In severe cases, leaves may turn almost white, leading to reduced yields.

Late Stage

In later stages, leaves turn completely white or yellow, sometimes with browning at the tips. Severe stunted growth, leaf loss, and reduced yield become evident.

Learn how to fix Iron deficiency.

Copper Deficiency (Cu)

Copper deficiency is relatively uncommon, but as it progresses, distinct color and texture changes become apparent. Recognize the symptoms at each stage:

Early Stage

In the early stage, leaves develop a bluish hue with purple undertones. Veins and leaf stems turn purple, and the edges may exhibit mild chlorosis or yellowing.

Progression

As the deficiency worsens, yellowing spreads across the entire leaf, accompanied by brown necrotic spots. Leaf curling, stiffness, and shiny appearance become noticeable.

Late Stage

In advanced stages, necrotic areas grow larger and darker. Leaves become crispy, brittle, and eventually fall off the plant.

Learn how to fix Copper deficiency.

Boron Deficiency (B)

Boron deficiencies are rare but can significantly impact plant health, quality, and yield. Detect this deficiency through the following stages:

Early Stage

• Subtle change in leaf color, often lighter or yellowish.
• Yellow leaves or yellowing along the edges, accompanied by yellow or brown spots.
• Deformed new growth, such as twisted stems or curling leaves.

Progression

• Yellowing and deformities affect older leaves and lower parts of the plant.
• Browning and death of growth tips and buds.
• Brittle, collapsed, or hollow stems.

Late Stage

• Severe growth issues, with growing tips dying off, leading to substantial crop loss.
• Complete necrosis, followed by the appearance of various diseases.

Learn how to fix Boron deficiency.

Manganese Deficiency (Mn)

Manganese deficiency can be challenging to detect due to subtle symptoms commonly associated with other deficiencies. Look for the following indicators:

• Yellowing of leaves and brown spots as the condition progresses.
• Yellowing and brown spots are common among various nutrient deficiencies, necessitating careful diagnosis.
• Manganese deficiencies are uncommon, so proper diagnosis is crucial.

Early Stages

• Slight discoloration, usually manifesting as yellow leaves.
• Mottled yellowing pattern of interveinal chlorosis, primarily in young leaves at the top of the plant.

Progression

• Intensified yellowing, with prominent signs of interveinal chlorosis. Leaf veins remain green, aiding diagnosis.

Late Stages

• Yellow areas turn into brown necrotic spots, and leaves curl, wilt, and eventually fall off.
• Severely stunted growth and potential loss of the entire crop.

Learn how to fix Manganese deficiency.

Sulphur Deficiency (S)

Inadequate sulphur levels can cause yellowing of leaves, stunted growth, and woody stems. Look for these key indicators:

Early Stage

• Newer leaves turning yellow while older ones remain green. Distinct from nitrogen deficiency, where yellowing begins at the bottom.
• Be cautious of light burns causing yellow top leaves. Sulphur deficiencies are rare, and cannabis plants need minimal amounts.

Progression

• Yellowing spreads to older leaves, turning the entire plant light green and eventually yellow. Growth slows, and aroma diminishes.

Late Stage

• Underside of leaves may exhibit reddish-purple or brown coloration.
• Development of woody stems and decreased yield.
• In some cases, surrendering and letting go of the plant may be necessary.

Learn how to fix Sulphur deficiency.

Silica Deficiency (Si)

Silica deficiencies are not common, but supplementing plants with Silica provides numerous benefits, including improved structure, pest resistance, disease prevention, and enhanced yield. Look out for these 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 notice yellowing cannabis leaves, don’t rush to assume it’s due to a nutrient deficiency. Often, yellow leaves are visible symptoms of more complex underlying issues. Consider the following common reasons:

• pH imbalance
• Temperature issues
• Light burns and leaf bleaching
• Under and overwatering
• Root rot
• Mite infestations
• Leaf Septoria
• Over/Under Fertilization

Learn about cannabis nutrient deficiencies.