Recognising nutrient deficiencies: Picture atlas for cannabis deficiencies

Identify nutrient deficiencies in cannabis quickly and safely:

**Nitrogen deficiency (N)**

*Symptoms:*

- Older leaves turn yellow, starting at the leaf tips

- Yellow colouring moves from bottom to top

- Leaves fall off prematurely

- Slower growth, thin stems

- Flowers remain small and airy

*Causes:*

- Too little nitrogen fertiliser

- pH value too high (>7.0) blocks N uptake

- Overwatering washes out nitrogen

- Pots too small, roots exhausted

*Immediate solution:*

- Nitrogen-rich fertiliser (NPK 20-10-10)

- adjust pH to 6.0-6.5 (soil)

- Blood meal for organic boost

- Liquid fertiliser for quick availability

**Phosphorus deficiency (P)**

*Symptoms:*

- Leaves turn dark green to purple/violet

- Red/purple leaf stems and veins

- Slow growth, delayed flowering

- Small, few flowers

- Affects older leaves first

*Causes:*

- Temperatures too low (<18°C)

- pH value too high or too low

- Excess calcium blocks P uptake

- Too little phosphorus fertiliser in bloom

*Immediate solution:*

- Phosphorus-rich flowering fertiliser (NPK 10-30-20)

- Increase temperature to 20-26°C

- check and correct pH value

- Bone meal for organic P source

**Potassium deficiency (K)**

*Symptoms:*

- Yellow/brown leaf edges ("burns")

- Leaves curl upwards

- Weak, thin stems

- Susceptibility to diseases/pests

- Poor flower development

*Causes:*

- Too little potassium in the flowering phase

- High calcium/magnesium levels block K

- Over-fertilisation with nitrogen

- Light stress increases K deficiency

*Immediate solution:*

- Potassium-rich fertiliser (NPK 5-10-30)

- Wood ash tea (organic)

- Reduce light intensity

- Pause calcium/magnesium applications

**Calcium deficiency (Ca)**

*Symptoms:*

- Brown, crispy spots on leaves

- New leaves deformed or curled

- Weak cell walls, soft stems

- Root tips die off

- "Bud rot" more susceptible

*Causes:*

- PH value too low (<6.0)

- Humidity too high (>70%)

- Insufficient aeration

- Soft water without calcium

*Immediate solution:*

- Cal-Mag-Supplement (2-4ml/L)

- increase pH to 6.2-6.8

- Reduce humidity to 40-60%

- Add gypsum (calcium sulphate) to the substrate

**Magnesium deficiency (Mg)**

*Symptoms:*

- Yellow spots between leaf veins (chlorosis)

- Leaf veins remain green

- Starts with older, middle leaves

- Leaves turn brown and die

- Poor light uptake

*Causes:*

- Too much potassium or calcium blocks Mg

- PH value too low

- Cold water (<18°C)

- LED light increases Mg requirement

*Immediate solution:*

- Epsom salt (magnesium sulphate) 1g/L

- adjust pH value to 6.5

- Heat water to room temperature

- Cal-Mag with a higher Mg content

**Iron deficiency (Fe)**

*Symptoms:*

- New leaves turn yellow, veins remain green

- Affects young shoot tips first

- Leaves turn almost white with severe deficiency

- Slowed growth of new shoots

*Causes:*

- pH value too high (>7.0)

- Excess phosphorus blocks Fe

- Too much zinc or