Nutrients — feeding cannabis from NPK to boron
Cannabis needs 17 elements. A single deficiency limits growth more than any light or climate gain can offset.
TL;DR: NPK veg 3-1-2, flower 1-3-2. Ca, Mg, S secondaries. Soil pH 6.0–6.8, coco/hydro 5.5–6.2. Measure runoff EC, not feed EC.
Macros, secondaries, micros
Macros N-P-K in grams. Secondaries Ca, Mg, S. Micros Fe, Mn, Zn, Cu, B, Mo in mg.
NPK by stage
Seedling 25 %. Veg 3-1-2. Flower 1-3-2. Bulking PK boost. Maturity drop N. Flush water only.
Cal-Mag
LED, coco, RO water: mandatory. 0.5–1 mL/L.
Visual deficiencies
N: old leaves uniformly yellow. P: purple stems. K: brown leaf edges. Ca: young-leaf necrosis. Mg: interveinal chlorosis.
FAQ
EC/pH meter required?
Yes — Bluelab or Milwaukee, $30–80.
PK boost needed?
Yes in mineral, no in living soil.