Cannabis Nutrient Deficiency Chart: Symptom Diagnosis Guide

This guide is educational and written for adult growers. Cultivation rules vary by country and region and change frequently. Before growing, verify current rules for your specific jurisdiction. Azarius does not provide formal advice. Always consult qualified professionals for health, safety, or formal matters relating to cultivation.

The cannabis nutrient deficiency chart at a glance

A cannabis nutrient deficiency chart is a diagnostic table that matches visible leaf symptoms — yellowing, spotting, clawing, purple stems — to the nutrient most likely behind them. It works because cannabis shows remarkably consistent symptom patterns across genetics, and because the mobility of each nutrient inside the plant dictates where on the plant the damage shows up first. Mobile nutrients (nitrogen, phosphorus, potassium, magnesium) get scavenged from old leaves and sent to new growth, so deficiencies appear at the bottom. Immobile nutrients (calcium, iron, sulphur, zinc, boron, manganese, copper) can't be reclaimed, so deficiencies hit the new growth at the top first (Bugbee, 2004).

AZARIUS · The cannabis nutrient deficiency chart at a glance

Before you trust the chart: 90% of what looks like a deficiency is actually a pH lockout. Cannabis in soil wants a root-zone pH of 6.0–6.8; in coco and hydro, 5.5–6.2. Outside that window, the nutrients can be sitting right there in the medium and the roots simply can't take them up (Mills & Jones, 1996). Always check pH and EC before you start chasing deficiencies with more feed.

Why mobility determines where you look

Mobility tells you where to look first: mobile nutrients damage old leaves, immobile ones damage new growth. This is the single most useful diagnostic trick in cannabis: look at which leaves are damaged before you guess the nutrient. Mobile nutrients travel through the phloem, so when the plant is short on nitrogen, it strips what it has from the oldest fan leaves and redirects it to new growth. You see yellowing at the bottom. Immobile nutrients — calcium and iron being the two you'll meet most often — can't be moved once they've been laid down in older tissue. A shortfall shows up on the new leaves at the top, because the plant simply can't build them properly (Marschner, 2012).

AZARIUS · Why mobility determines where you look

Get this reflex and half the chart diagnoses itself. Yellow bottom leaves = probably nitrogen. Yellow top leaves = probably iron or calcium, and almost always a pH problem rather than an actual shortage in the feed.

pH lockout — the thing that isn't a deficiency

pH lockout is when correctly-dosed nutrients become chemically unavailable to the roots because the root-zone pH has drifted outside the usable window. Nutrient availability is a pH-dependent curve. Iron, manganese, zinc, and phosphorus all drop out of solution above pH 6.5–6.8 in soilless media; calcium and magnesium struggle below 5.5. You can be feeding a perfect blend and still see a textbook iron deficiency because your runoff is reading 7.2 (Bugbee, 2004).

AZARIUS · pH lockout — the thing that isn't a deficiency

Target ranges we stick to in our own tent:

• Soil: pH 6.0–6.8, EC 1.0–1.8 mS/cm in veg, up to 2.2 in flower
• Coco coir: pH 5.8–6.2, EC 1.2–2.0 mS/cm, feed every watering with Cal-Mag
• Hydroponics (DWC/NFT): pH 5.5–6.0, EC 1.2–1.8 mS/cm, reservoir watched daily

Honest limitation: a cheap pH pen that hasn't been calibrated in a month will lie to you by 0.3–0.5 points, which is enough to fake a lockout that isn't really there. Calibrate before every diagnostic reading, or don't trust the number. If you buy a pH pen, get a decent one with calibration solution in the box — it pays for itself the first time it saves a plant.

If symptoms appear across multiple nutrients at once — iron and calcium together, say — the medium is almost certainly out of range. Fix the pH first, wait 3–4 days, and re-read the plant.

The three confusions that catch everyone

Three symptom patterns get misdiagnosed more than any others: nute burn mistaken for potassium deficiency, coco-related Cal-Mag shortage mistaken for generic yellowing, and natural flower fade mistaken for nitrogen deficiency.

AZARIUS · The three confusions that catch everyone

Nute burn vs potassium deficiency. Both give you burnt leaf tips. Nute burn starts uniformly across the canopy with EC too high; K deficiency starts on lower leaves with interveinal yellowing creeping in behind the burn. Check runoff EC — above 2.5 mS/cm in soil and you're overfeeding.

Calcium vs magnesium in coco. Coco coir holds onto potassium and releases it slowly while binding calcium and magnesium. Growers running coco without Cal-Mag supplementation see a predictable cascade: Mg interveinal yellowing on mid-leaves, Ca spotting on new growth, within 2–3 weeks of flip. Add Cal-Mag from day one in coco; it's not optional.

Natural flower fade vs nitrogen deficiency. From week 5–6 of flower onward, fan leaves yellow and drop as the plant remobilises nitrogen into the buds. This is normal and desirable. If the entire plant is yellowing by week 3, that's a real deficiency. If only the lower fans are fading at week 7, leave it alone.

A diagnostic workflow that actually works

Work through four steps in order before you buy another bottle of feed: check runoff, locate the damage, check the environment, then make one change at a time.

AZARIUS · A diagnostic workflow that actually works

1. Check runoff pH and EC. Collect 50 ml of runoff from the next watering. This tells you what the roots are actually experiencing, not what you poured in.
2. Locate the damage. Top, middle, or bottom of the plant? New growth or old? Use the mobility logic.
3. Check the environment. Root-zone temperature below 15 °C locks out phosphorus. Ambient humidity above 70% reduces transpiration and slows calcium uptake (Hochmuth, 2011).
4. One change at a time. Adjust pH, or add Cal-Mag, or reduce EC — not all three at once. Wait 4–5 days. Symptoms stop spreading before damaged leaves recover; judge by new growth, not old.

When it's excess, not deficiency

Excess of one nutrient often shows up as a deficiency of another. Excess nitrogen causes dark, clawing leaves and suppresses calcium uptake. Excess potassium blocks magnesium. Excess phosphorus in flower boosters can lock out zinc and iron. If you've been steadily pushing EC up and the plant is getting more symptoms, not fewer, the answer is usually a flush with plain pH'd water at EC 0.3–0.5, then restart feeding at 60% of previous strength.

AZARIUS · When it's excess, not deficiency

Cannabis does most of its damage to itself through overfeeding, not underfeeding. Published cultivar trials show healthy growth across an EC range of 1.2–2.2 mS/cm depending on stage and genetics (Caplan et al., 2017) — higher isn't better.

Last updated: April 2026