Cannabis Nutrient Deficiency Chart

Cannabis Nutrient Deficiency Chart: Diagnose and Fix Fast

If you've got plants in front of you and something looks wrong, you're in the right place. This cannabis nutrient deficiency chart covers every major macro and micronutrient issue you'll encounter — what it looks like, what's actually causing it, and exactly how to fix it. Across 1,000 grow journals tracked on Grow Guide, the overwhelming majority of nutrient problems occur in soil grows (632 out of 1,000), where pH drift is the number-one culprit behind apparent deficiencies. Before you reach for a bottle of supplements, check your pH. You'd be surprised how often that's the whole story.

If you want an interactive version of this guide, our Nutrient Deficiency Identifier walks you through a symptom checklist and returns a diagnosis in under a minute.

How to Read Deficiency Symptoms

The single most important diagnostic rule: location on the plant tells you almost everything. Mobile nutrients — nitrogen, phosphorus, potassium, and magnesium — move from old growth to new growth when supply runs short, so deficiency symptoms appear on older, lower leaves first. Immobile nutrients — calcium, iron, zinc, manganese, boron — can't relocate, so those deficiencies show up on new growth first.

The Cannabis Nutrient Deficiency Chart: Macronutrients

Nitrogen Deficiency

What it looks like: Uniform pale yellowing starting on the lowest, oldest fan leaves, progressing steadily upward. The whole leaf fades — not just between the veins — and affected leaves eventually drop. The plant looks generally washed out. In veg this is a red flag; in late flower (week 7+) some lower-leaf yellowing is completely normal and expected.

What causes it: Underfeeding is the obvious one, but pH drift is just as common. At soil pH above 7.0 or below 5.5, nitrogen uptake tanks. Also watch out for overwatering — waterlogged roots can't absorb nitrogen even when it's sitting right there.

How to fix it: Check pH first (target 6.0–6.5 in soil). If pH is fine, increase nitrogen by 25–30% on your next feed. Use a high-N veg formula or add a nitrogen supplement like fish emulsion at 5–10 ml/L. You should see new growth improving within 5–7 days; yellowed leaves won't recover, but the upward march of yellowing will stop.

How to prevent it: Feed according to a defined schedule and track EC. Veg-stage EC should run 1.2–2.0 mS/cm in soil. Use our Grow Schedule Planner to map out your nutrient ramp so you're never guessing what to feed and when.

Phosphorus Deficiency

What it looks like: Dark green to bluish-green foliage, sometimes with a bronze or purple sheen on the undersides of leaves and along stems. Growth slows noticeably. In severe cases leaves develop brown spots before dying. Unlike nitrogen, the leaves don't turn uniformly pale — they stay dark until things get bad.

What causes it: Cold root zones are the most underrated cause. Below 18°C (64°F), phosphorus uptake shuts down even when the nutrient is present. High pH (above 7.0 in soil) also causes phosphorus lockout. Overfeeding calcium can compete with phosphorus uptake too.

How to fix it: Warm the root zone to at least 20–22°C before touching your nutrient mix. If temps are fine, check pH and flush with plain pH-corrected water (2–3x the pot volume) before reintroducing nutrients at 50% strength. Add a bloom booster with elevated P during weeks 3–6 of flower (look for P values of 5–10 on the label).

How to prevent it: In winter grows or cold basements, use a seedling heat mat under fabric pots to keep roots warm. Monitor root zone temp, not just ambient air temp.

Potassium Deficiency

What it looks like: Older leaves develop marginal scorch — the leaf edges brown and curl upward as if burned. The leaves may first turn pale or yellow before the edges die. Stems can feel weaker and flexible. During flower, bud size and density suffer noticeably if potassium runs low.

What causes it: Inadequate potassium in the nutrient mix, or pH out of range (optimal soil absorption is 6.0–6.5). Excess sodium from tap water can also block potassium absorption competitively.

How to fix it: Confirm pH is in range. Switch to a bloom-phase nutrient formula with elevated K (look for K values of 7–12 on the NPK label). Potassium sulfate or a potassium silicate supplement can be added at 1–2 ml/L. Results show in new growth within 4–6 days.

How to prevent it: Transition to a bloom-focused nutrient formula at the first sign of flowering — don't keep running veg nutrients into week 2 or 3 of flower as many growers do. See our guide on Best Organic Nutrients for Cannabis for bloom-phase product recommendations.

Cannabis Nutrient Deficiency Chart: Micronutrients

Iron Deficiency

What it looks like: New leaves emerge yellow while the veins stay distinctly green — this interveinal chlorosis on the newest growth is the classic iron deficiency signature. The contrast between yellow leaf tissue and green veins is sharp and obvious.

What causes it: High pH (above 6.8 in soil, above 6.2 in coco/hydro) makes iron insoluble. Excess phosphorus also competes with iron absorption. This is one of the most common deficiencies in over-fertilized grows.

How to fix it: Lower pH to 6.0–6.3 in soil, 5.6–5.9 in coco. Apply an iron chelate foliar spray (iron EDTA or DTPA at 1–2 g per 10L of water) for rapid uptake — foliar iron bypasses root pH issues and shows results within 48–72 hours. Follow up with root-zone pH correction so it doesn't keep recurring.

Zinc Deficiency

What it looks like: New leaves are small, sometimes twisted or asymmetric, with shortened internodal spacing. Interveinal chlorosis appears on the newest growth. Flower sites can stall, and bud structure looks loose or underdeveloped.

What causes it: High pH and excess phosphorus are the main culprits — they block zinc absorption at the root surface. Zinc deficiency in cannabis is almost always a pH or overfeeding problem, not a true absence of zinc.

How to fix it: Correct pH to 5.8–6.2 in soil. Flush once if you suspect phosphorus buildup. Add zinc sulfate at 1 ml/L or use a micronutrient supplement containing zinc. New growth should normalize within 5–10 days.

Manganese Deficiency

What it looks like: Similar to iron deficiency — interveinal chlorosis on new leaves — but typically milder in contrast and affects mid-canopy as much as the very top. Affected leaves may develop tan or gray speckling as the deficiency progresses.

What causes it: Alkaline soil, excess calcium or iron, or consistently high-pH water. Manganese gets locked out above pH 6.8 in soil very reliably.

How to fix it: Adjust pH down to 6.0–6.5. Apply manganese sulfate at 1–2 g per 10L, either as a foliar spray or through root drenching. A broad-spectrum micronutrient supplement (containing Fe, Zn, Mn, B together) is often the most efficient approach for mixed micronutrient lockout situations.

Calcium and Magnesium Deficiency

What it looks like: Calcium: New growth is twisted, cupped, or necrotic at the tips with irregular brown spots. Magnesium: Older leaves develop interveinal yellowing, creating a green-veined, yellow-tissue appearance on mid and lower fan leaves. Cal-mag deficiency is extremely common in coco coir grows — coco has a natural cation exchange bias that strips calcium and magnesium before plants can use them.

How to fix it: Add cal-mag supplement at 2–5 ml/L. For coco growers, cal-mag should be a baseline addition from day one at 1–2 ml/L, ramping to 3–5 ml/L in flower. Soil growers can use dolomite lime as a preventive buffer (5–10 g per gallon of soil at mixing). For seedlings specifically, see our article on best nutrients for cannabis seedlings which covers cal-mag baseline dosing for young plants.

Step-by-Step Fix: The 4-Step Deficiency Protocol

Quick-Reference Cannabis Nutrient Deficiency Chart Table

Preventing Nutrient Deficiencies: The Non-Negotiables

• pH meter calibration: Calibrate with fresh buffer solution every 2 weeks. A drifted meter is the number one reason growers are convinced they have a deficiency when they actually have a measurement problem.
• EC tracking: Keep runoff EC within 0.2–0.5 mS/cm of input EC. Wide gaps signal buildup (flush) or near-empty medium (increase feed).
• Water pH every single feed: In our platform data, the majority of growers watering manually (547 out of 1,000) are the most susceptible to pH drift because they're not using automated dosing systems. Hand-water growers should pH every feed, every time — no exceptions.
• Match nutrients to stage: High-N veg formulas in flower = potassium and phosphorus deficiency. Switch your formula at the flip, not weeks later.
• Log symptoms as they appear: Keeping a dated grow journal means you'll spot patterns across grows. Our Cannabis Grow Diary guide shows you exactly how to track nutrient notes effectively.

If you want to see how nutrient issues affect your final output, plug your numbers into our Yield Calculator — it accounts for plant stress days and recovery time when estimating final gram counts. And if you're still unsure what's wrong with your plant, our Nutrient Deficiency Identifier takes you through a quick symptom checklist to get you a diagnosis right now.