NPK Explained: What Cannabis Needs at Each Stage
The three numbers on a nutrient bottle are the percentages of nitrogen, phosphorus, and potassium. The plant wants a different ratio at each stage of its life.
Nitrogen (N) — vegetative growth
Nitrogen builds leaves and stems. Veg feeds run nitrogen-heavy, something like 3-1-2. Nitrogen is mobile in the plant, so deficiency shows first as uniform yellowing on the oldest, lowest leaves.
Phosphorus (P) — flower formation
Phosphorus drives root development and flower set. Bloom feeds shift toward it, but excessive phosphorus is a common home-grow mistake that locks out zinc and iron.
Potassium (K) — bulking and water regulation
Potassium is the workhorse of late flower, regulating stomata and moving sugars into the bud. Late-flower ratios often look like 1-3-4.
Do not forget the rest
Calcium, magnesium, and sulfur are secondary nutrients consumed in real quantity, and iron, zinc, manganese, boron, copper, and molybdenum in trace amounts. A three-part base plus Cal-Mag covers all of it for most growers.
Frequently asked questions
- Do I need a bloom booster?
- Usually no. A complete three-part base line shifted to a bloom ratio already delivers what the plant uses.