Cannabis Deficiency Chart: Symptoms & Fixes

Yellow, spotted or curling leaves are the plant telling you something is wrong — but many deficiencies look alike, and the wrong fix can create a second problem. This chart helps you narrow it down in three questions: where the symptom started, what it looks like, and what your pH says. In most grows, the real cause is not a missing nutrient but a nutrient the plant can't take up: pH drift, inconsistent dosing, cold or waterlogged roots, or one element blocking another.

Step 1: Where did the symptoms start?

This is the fastest way to narrow the list. Mobile nutrients can be moved by the plant from old leaves to new growth, so shortages show at the bottom first. Immobile nutrients stay where they were laid down, so shortages show at the top first.

Where symptoms appear first	Nutrient mobility	Likely deficiencies
Older, lower leaves	Mobile	Nitrogen, phosphorus, potassium, magnesium
New growth and upper leaves	Immobile or limited mobility	Calcium, iron, zinc, manganese, boron

Step 2: The cannabis nutrient deficiency chart

Nutrient	Where it starts	Key visual signs	Peak demand	Ideal pH (soil / hydro & coco)	Most common causes	Often confused with
Nitrogen (N)	Older, lower leaves	Uniform pale green to yellow leaves, veins included; leaves drop from the bottom	Vegetative stage	6.0–7.0 / 5.5–6.5	Underfeeding in veg, pH drift, overwatering, root-bound plants	Normal late-flower fade, magnesium deficiency
Phosphorus (P)	Older, lower leaves	Dark blue-green leaves, purple stems and petioles, bronze or brown blotches	Transition to flower, early bulking	6.2–7.0 / 5.5–6.2	pH lockout, low P in bloom feed, cold root zone, hard water	Natural purple genetics, cold stress
Potassium (K)	Older and middle leaves	Yellow-to-brown burnt leaf edges moving inward, rusty margin spots, upward curl	Mid-flower to bulking	6.0–7.0 / 5.5–6.5	pH, low K in flower, excess Ca/Mg/Na, salt buildup, heat	Nutrient burn, heat/light stress
Magnesium (Mg)	Older and middle leaves	Yellowing between green veins, rust or purple spots, brittle upward-curling leaves	Mid-to-late flower	6.0–7.0 / 5.5–6.5	RO or soft water, unbuffered coco, excess K or Ca, low pH	Nitrogen deficiency, potassium deficiency
Calcium (Ca)	New growth, upper leaves	Brown or bronze spots with defined edges, twisted or crinkled new leaves, weak stems	Fast veg and early flower	6.2–7.0 / 5.8–6.2	RO water, unbuffered coco, excess K/Mg/NH4, high humidity	Magnesium deficiency, pest damage, pH swings
Iron (Fe)	Newest leaves at the top	Pale yellow new leaves with green veins; whitish tops in severe cases	All stages	6.0–6.5 / 5.5–6.0	pH too high (main cause), overwatering, hard alkaline water	Magnesium (older leaves), manganese
Zinc (Zn)	New growth	Yellowing between veins on small, narrow, twisted new leaves; very short internodes	Veg and early flower	6.0–6.5 / 5.5–6.2	High pH, excess phosphorus from bloom boosters	Iron or manganese deficiency
Manganese (Mn)	Young and middle leaves	Mottled yellowing between green veins, scattered brown or tan spots	All stages	6.0–6.5 / 5.5–6.2	High pH, excess iron, poor root health	Iron deficiency, low-pH Mn toxicity
Boron (B)	Growing tips, new growth	Thick, brittle, distorted new leaves; tips that brown and die; hollow stems	Fast growth and flowering	6.0–6.5 / 5.5–6.2	Low transpiration (high humidity), high pH, RO water, leaching	Calcium deficiency, heat stress, pests

Note: pH targets are general growing guidance for mineral nutrient programs. Always follow your nutrient manufacturer's recommendations and confirm with a leaf tissue or water test when in doubt.

Step 3: Rule out the look-alikes

Before adding any supplement, check that the symptom is not caused by something else. These are the most common misdiagnoses:

Look-alike	What it looks like	How to tell the difference
Nutrient burn (overfeeding)	Brown, crispy tips only, often with dark green leaves	Only the very tips are affected; runoff EC is higher than input EC
pH fluctuation	Mixed symptoms from several "deficiencies" at once	Several nutrients appear short at the same time; pH at input or runoff is outside range
Light or heat stress	Bleached or yellow tops closest to the lamp, upward-curling "tacoing" leaves	Symptoms limited to the top of the canopy, directly under the light
Overwatering	Droopy, swollen leaves, slow growth, general yellowing	Media stays wet; plants recover once dry-back is restored
Natural late-flower fade	Gradual yellowing of fan leaves in the final weeks	Happens near harvest, buds keep ripening normally
Genetic purpling	Purple stems, leaves or buds	Healthy leaf color and normal growth; common with cool nights

Step 4: Fix the cause, not just the symptom

Check pH and EC at input and runoff (or in the reservoir for hydro). It is the root cause in most cases.
If runoff EC is much higher than input, or pH is far off, flush with pH-adjusted water and restart at the right concentration.
Check your source water. RO and soft water need Cal-Mag; hard, alkaline water may need acid injection.
Correct the feed for the growth stage: more nitrogen in veg, more phosphorus and potassium in flower — without overdoing boosters.
Fix the root zone: proper dry-back, good drainage, and root-zone temperature around 65–75°F (18–24°C).
Judge success on new growth. Damaged leaves rarely recover; healthy new leaves within one to two weeks mean the fix worked.

Too much is a problem too

Overcorrecting is one of the most common mistakes. Many nutrients compete for uptake, so pushing one can lock out another:

Excess of…	Can cause a deficiency in…
Potassium (K)	Calcium, magnesium
Phosphorus (P)	Zinc, iron, calcium
Calcium (Ca)	Magnesium, potassium, boron
Iron (Fe)	Manganese, zinc
Zinc (Zn)	Iron
Nitrogen (N)	Delayed ripening, leafy buds and "the claw" (dark, downward-curling leaf tips)
Boron (B) / Manganese (Mn)	Direct toxicity — boron has a very narrow safe range; manganese becomes toxic when pH runs too low

Why consistent dosing prevents most deficiencies

Most deficiencies come from a nutrient solution that drifts: a stock tank mixed by hand, a feed that changes with water pressure, or incompatible fertilizers mixed in one concentrate. Dosatron water-powered proportional pumps inject concentrated nutrients, Cal-Mag, micronutrients and pH adjusters directly into the irrigation line at a constant ratio, whatever the flow or pressure. Every plant gets the same feed, from the first bench to the last. Installing units in series lets you keep calcium separate from phosphates and sulfates, dose micronutrients in tiny, stable amounts, and adjust the feed for veg or flower in seconds — with no electricity required.

Want to know more about the right dosing setup for your cannabis operation.

Cannabis Nutrient Deficiency Chart