Cannabis Nutrient Deficiency Chart 2026: Identify and Fix Symptoms Fast
Walk into any grow room with yellowing leaves and you will hear three different diagnoses in five minutes. The truth is most cannabis nutrient problems are not what they look like at first glance. A nitrogen-deficient plant and a pH-locked plant can look identical, and the wrong fix makes both worse.
Mobile vs Immobile Deficiencies
The single most useful diagnostic skill in cannabis growing is reading where on the plant the symptom appears first.
Mobile Nutrients (Damage on Lower, Older Leaves First)
- Nitrogen (N)
- Phosphorus (P)
- Potassium (K)
- Magnesium (Mg)
Immobile Nutrients (Damage on New Growth at Top First)
- Calcium (Ca)
- Sulfur (S)
- Iron (Fe)
- Manganese (Mn)
- Zinc (Zn)
- Boron (B)
- Copper (Cu)
Quick Rule: Yellow on the bottom = mobile nutrient. Yellow on top = immobile nutrient.
The Big Three Macronutrients: N, P, K
Nitrogen Deficiency (Mobile)
Symptoms: Pale lower leaves, uniform yellowing, leaves drop with a light tug, slow vertical growth.
Fix: Bump the nitrogen-heavy base nutrient by 15 to 25 percent, or top dress with a balanced organic amendment in soil.
Phosphorus Deficiency (Mobile)
Symptoms: Dark blue-green older leaves, purple or bronze splotches, red stems, slow flowering.
Fix: Check root zone temperature first (cold roots mimic P deficiency). If temps are fine, increase a P-K bloom booster and verify pH.
Potassium Deficiency (Mobile)
Symptoms: Brown crispy edges and tips on lower leaves, leaf curl, stretched internodes, fluffy buds.
Fix: Switch to a bloom formula with a higher K ratio.
Secondary Nutrients: Ca, Mg, S
Calcium Deficiency (Immobile)
Symptoms: Twisted or hooked new growth, brown spotting on young leaves, weak stems.
Fix: Add a Cal-Mag supplement at 2 to 5 mL per gallon.
Magnesium Deficiency (Mobile)
Symptoms: Interveinal yellowing on lower leaves with green veins, rusty brown spots in advanced cases.
Fix: Cal-Mag supplement, or a foliar spray with Epsom salt.
Sulfur Deficiency (Immobile)
Symptoms: Uniform pale yellowing on upper, newer leaves, purple petioles.
Fix: Most base nutrients contain enough sulfur.
Micronutrients
Iron Deficiency (Immobile)
Symptoms: Bright yellow new leaves with green veins. Almost always a pH problem.
Fix: Correct pH first.
Manganese, Zinc, Boron
All immobile. Usually triggered by high pH lockout.
The Hidden Killer: pH Lockout
Target pH: Soil 6.2 to 6.8. Coco 5.8 to 6.2. Hydro and DWC 5.5 to 6.1.
If symptoms hit multiple nutrient groups at once, pH is the cause 90 percent of the time.
Fix vs Flush
When to Adjust the Feed
Single mobile nutrient symptom early, EC low to normal, pH on target: bump the relevant ratio in your next feed.
When to Flush
- Runoff EC is high (above 2.0 in soil)
- Salt buildup or crust visible on the soil surface
- Multiple symptoms at once with no clear single cause
Water Quality
- Tap water: Often 100 to 400 ppm starting EC.
- RO water: Near zero ppm. Always add Cal-Mag.
- Well water: Test it.
Soil vs Hydro Differences
Soil
Soil buffers pH and nutrient swings, which gives you more reaction time.
Coco Coir
Treated as semi-hydro. Coco binds calcium and magnesium, so Cal-Mag is mandatory.
Hydroponics
No buffer. Problems show up within hours.
When to Suspect Overfeeding
- Brown, crispy tips on the youngest, biggest fan leaves.
- Leaf tips curl down or claw.
- Dark, glossy, almost waxy green color overall.
Quick Diagnostic Decision Tree
- Multiple unrelated symptoms? Check pH and runoff EC.
- Youngest top leaves burned? Nutrient burn.
- Yellowing on LOWER leaves? Mobile nutrient.
- Damage on UPPER, new leaves? Immobile nutrient.
- Symptom only on growing tip? Root health or boron issue.
- Did you change anything in the last 5 days? Most likely cause.
Conclusion
Read where on the plant the symptom appears, check pH and EC before adding anything, and rule out overfeeding before you assume a shortage.
Browse our full library of growing weed guides for deeper dives on feeding schedules, pH management, and training techniques.
