Nutrient deficiency chart
First rule: most "deficiencies" are pH problems. Before adding anything, check root-zone pH against the pH-by-medium table — lockout mimics deficiency.
| Nutrient | Symptoms | Mobility | Notes |
|---|---|---|---|
| Nitrogen (N) | Older/lower leaves yellow first, whole plant pales, early leaf drop | Mobile — moves to new growth | Common in late veg with light feeding |
| Phosphorus (P) | Dark blue-green leaves, purple stems/petioles, slow growth | Mobile | Often cold-root related, not true deficiency |
| Potassium (K) | Leaf-edge scorch/burn on older leaves, weak stems | Mobile | Shows mid-flower when demand spikes |
| Calcium (Ca) | New growth distorted/hooked, brown spots on younger leaves | Immobile — new growth suffers | Frequent in coco without cal-mag |
| Magnesium (Mg) | Interveinal yellowing on older leaves (green veins, yellow tissue) | Mobile | Classic mid/late-flower fade — sometimes intentional |
| Iron (Fe) | New growth yellows almost white, veins stay green | Immobile | Usually pH lockout, not missing iron |
Mobile nutrients show on OLD growth first (plant cannibalizes it); immobile ones show on NEW growth. That single distinction rules out half the chart at a glance.
Common questions
Why do some deficiencies show on old leaves and others on new?
Mobility. Nitrogen, phosphorus, potassium and magnesium move through the phloem, so the plant strips them from old leaves to feed new growth — symptoms appear at the bottom. Calcium, iron and boron cannot be moved once placed, so symptoms appear in new growth at the top.
Nitrogen or magnesium — how do I tell them apart?
Both yellow the lower leaves, but the pattern differs: nitrogen fades the whole leaf fairly evenly, while magnesium yellows between the veins and leaves the veins themselves green.
Do these rules hold in flower?
Not entirely, and this is worth knowing. Research on flowering cannabis found calcium deficiency starting in the LOWER fan leaves — the opposite of the textbook pattern in most plants. Late-flower senescence is also routinely mistaken for deficiency.
Should I feed more if leaves are yellowing?
Not before checking pH. If root-zone pH is out of band the nutrient is present but unavailable, and adding more makes salt build-up worse without fixing the cause.
Sources: Cockson et al. 2019, Applied Sciences — induced deficiencies in cannabis, photographed · Llewellyn et al. 2023, Plants — flowering cannabis breaks the textbook pattern · Maillard et al. 2015, Frontiers in Plant Science — why mobile nutrients show in old leaves · Montana State Extension NM-9 — mobile vs immobile nutrients
- Cal-mag supplement — the single most common fix in coco and under LEDs
- Digital pH pen + calibration solution — most 'deficiencies' are pH lockout — measure before you feed
Affiliate links: we may earn a small commission at no cost to you. We only list gear that solves the problem on this page. Disclosures.
Keep reading
- pH ranges by growing medium (fix the cause, not the symptom)
- Not sure which one it is? Free photo diagnosis
- Environment targets by stage
Track your own grow free — the journal grades your environment against these bands →
Get the one-page grow reference card
VPD, pH by medium, deficiency symptoms and dry/cure targets on a single printable page. Free — plus the occasional grow-data breakdown. No spam, unsubscribe in one click.