Pick where the problem started and what the leaves look like, and the chart narrows the 13 plant nutrients down to the likely few, with the pH notes and the fix for each. Mobile nutrients (nitrogen, phosphorus, potassium, magnesium, molybdenum) show on the oldest, lowest leaves first; immobile ones (calcium, sulphur, iron, manganese, zinc, boron, copper) show on new growth at the top first. Check pH before adding anything: most deficiencies are pH lockout. Around 6.0–7.0 suits soil and 5.5–6.5 suits coco and hydro.
| Nutrient | Where it starts | Symptoms | pH | Fix |
|---|---|---|---|---|
| Nitrogen (N) Mobile | Old, lower leaves first | Leaves turn pale green to yellow, starting on the oldest, lowest leaves and moving up. Veins and leaf stems may show red or purple tints, and the plant loses vigour. | Availability drops in strongly acidic or alkaline conditions. | Check pH first, then feed a nutrient with more nitrogen (a veg or grow formula). A few yellow lower leaves late in flower is normal as the plant uses up its stores. |
| Phosphorus (P) Mobile | Old, lower leaves first | Slow growth with dark green older leaves early on, then bronze tints with browning between the veins and at the edges. Leaflets stay small and spindly, maturity is delayed and buds may be fewer and smaller. | Availability begins to fall below pH 6. | Correct pH, keep the root zone warm, and feed a nutrient with phosphorus (a bloom formula in flower). Purple stems alone are not proof: purpling is a general stress response. |
| Potassium (K) Mobile | Old, lower leaves first | Yellowing and browning of the leaf edges ('marginal scorch'), first on older leaves, which often curl downward. Internodes may be shorter. | Availability falls below pH 6 and is reduced between pH 7.6 and 8.4. | Correct pH and feed a nutrient with potassium. If you also see salt build-up, flush the medium with pH-balanced water first. |
| Calcium (Ca) Immobile | New growth first | New growth turns pale, then develops yellow-to-brown spots and dead patches between the veins. Leaves can curl and grow in odd shapes, and in severe cases the growing tips stop and die back. | Availability declines below pH 6.5. Uptake is also blocked by ammonium-based nitrogen and by excess potassium, magnesium or manganese. | Correct pH and add calcium, for example a Cal-Mag (calcium-magnesium) supplement. |
| Magnesium (Mg) Mobile | Old, lower leaves first | Yellowing (or reddening) between the veins of older leaves while the veins stay green, followed by browning at the edges, curling and dead patches. It can run for weeks before you see it. | Most available between pH 6.5 and 8.5. | Correct pH and add magnesium: a Cal-Mag supplement or Epsom salt (magnesium sulphate). |
| Sulphur (S) Immobile | New growth first | The plant turns pale green, with younger leaves more yellow than older ones and sometimes red or purple tints. Stems can look woody with short internodes. | Availability falls below pH 6.0. | Correct pH; a complete nutrient (or Epsom salt, which also contains sulphur) usually solves it. |
| Boron (B) Immobile | New growth first | New leaves come out distorted and curled and thicken with age, with yellowing between the veins and then dead tissue. Growing tips can die back and buds may be deformed. | Availability declines above pH 7.5. | Correct pH and use a complete nutrient with micronutrients. Add boron only in tiny amounts: the gap between too little and too much is narrow. |
| Chlorine (Cl) Mobile | New growth first | Rare. Growth slows, growing tips and young leaves wilt or go limp, then yellow and dead spots appear; young leaves may cup. | Not affected by pH. | Very rare in practice: tap water and most nutrients supply enough chloride. |
| Copper (Cu) Immobile | New growth first | New growth turns an unusual dark blue-green and looks wilted, then yellows and starts to curl and droop. | Availability declines above pH 8.0. | Rare. Correct pH and use a complete nutrient with micronutrients. |
| Iron (Fe) Immobile | New growth first | Young leaves at the top of the plant turn yellow between the veins, from light green to pale yellow or almost white, while the veins stay green. Brown dead patches appear only after a long deficiency. | Availability declines above pH 7.5. Overwatering, poor drainage and cold roots make it worse. | Lower the pH if it is high, ease off watering, and use a chelated iron product if needed. |
| Manganese (Mn) Immobile | New growth first | Young leaves yellow between the veins while the edges and veins stay darker green, then develop brown speckles or dead patches. | Availability declines above pH 7.5. | Correct pH and use a complete nutrient with micronutrients. |
| Molybdenum (Mo) Mobile | Old, lower leaves first | Looks like nitrogen deficiency: yellowing, stunting and scorched leaf edges, starting on older leaves, with leaves cupping or rolling. Yellow spots can appear on young and old leaves. | Availability increases above pH 7.0, so deficiency is more likely in acidic conditions. | Raise the pH if it is too low and use a complete nutrient with micronutrients. |
| Zinc (Zn) Immobile | New growth first | The newest leaves yellow between the veins, sometimes as pale or white bands; in severe cases new leaves come out almost white. New leaves can also be thin and narrow with distorted edges. | Availability declines above pH 8.0. | Correct pH and use a complete nutrient with micronutrients. |
Symptoms, mobility and pH notes follow the Ontario Ministry of Agriculture Nutrient Deficiency Identification Guide for Hemp (2023) and Utah State University Extension hemp nutrient guidance.
Start with where the symptoms appeared first. Mobile nutrients (nitrogen, phosphorus, potassium, magnesium, molybdenum) show on the oldest, lowest leaves first; immobile ones (calcium, sulphur, iron, manganese, zinc, boron, copper) show on new growth at the top first. Then match the pattern: overall yellowing, yellow between green veins, brown spots or edges, or distorted leaves.
Often it is pH. Each nutrient becomes harder for roots to take up outside its pH range, so a plant can show a deficiency even when the nutrient is in the soil. Check the pH of your water and runoff before adding anything: around 6.0–7.0 for soil and 5.5–6.5 for coco and hydro.
Not on their own. Purpling comes from anthocyanin, a general stress response, and cold, genetics and other problems can cause it. Phosphorus deficiency usually also shows slow growth, dark green older leaves that later bronze and brown, and small leaflets.
Usually not. In the last weeks of flower the plant moves nitrogen out of its older fan leaves, so they yellow and drop. It is a problem when yellowing starts early, spreads fast or reaches the upper leaves and buds.
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