Short answer
Cannabis uses more nitrogen in veg and more phosphorus and potassium in flower. A 3-1-2 N-P-K ratio fits veg. A 1-3-2 or 1-4-3 ratio fits weeks 1 to 6 of flower. Target 1.2 to 1.6 EC in veg and 1.4 to 2.0 EC in flower for photoperiod plants in coco or peat mixes. Set pH at 5.8 to 6.2 in soilless media and 6.2 to 6.8 in soil.
when to start feeding cannabis seedlings
Veg stage: what the plant takes
Veg runs 3 to 8 weeks under 18/6 light. The plant builds stems and leaves, so nitrogen drives the schedule. Tissue tests on hemp show nitrogen uptake peaks in this window. Calcium and magnesium move with the nitrogen, so most veg formulas carry 2 to 4 percent Ca and 0.5 to 1.5 percent Mg. Iron and manganese stay available below pH 6.5 in soilless systems.
Cannabis in veg tolerates 1.2 to 1.6 EC. Above 2.0 EC, leaf tips burn and root zone salts build. Feed, water, water is a common rotation in coco.
marijuana feeding schedule week by week
Flower stage: what changes
Flower runs 7 to 11 weeks for most photoperiod cultivars. Nitrogen drops to 1 to 2 percent of the formula by week 4. Phosphorus and potassium rise. Potassium demand peaks in weeks 4 to 7, when bud mass accumulates. Many schedules cut nitrogen at week 6 and hold PK to week 8.
cannabis nutrient feeding chart for soil
EC climbs from 1.4 to 2.0. Runoff EC should stay within 0.3 of the input value. A gap above 0.5 means salt buildup and a flush is due.
Autoflowers and short cycles
Autoflowering cultivars finish in 70 to 90 days from seed. Veg lasts 3 to 4 weeks. There is no light flip to signal the change, so the nutrient switch comes from the calendar, not the plant. Feed a veg ratio for 21 to 28 days, then move to a flower ratio at 1.2 to 1.6 EC. Autoflowers take lower EC than photoperiods at every stage.
Where convenience fits
Convenience now drives purchase more than ratio. One-part liquid nutrients fix N-P-K for the whole cycle, so the grower cannot drop nitrogen at week 6. Two-part A/B systems cost more time at the mix station but allow the ratio shift. Dry amendments on pre-charged soil cover 4 to 6 weeks with no mixing. Water-only systems remove the EC meter from the workflow and put the burden on the soil blend.
None of these formats changes plant demand. They change the number of steps and the number of measurements per week. A one-part bottle at 1.5 EC in veg and 1.8 EC in flower will finish a crop. A two-part system will finish the same crop with more control over nitrogen.
Mixing rules that hold across formats
- Add part A and part B in separate steps. Calcium in A and phosphate or sulfate in B form gypsum or calcium phosphate if they meet at full strength.
- Measure EC after all parts are in, not before.
- Adjust pH last.
- Keep reservoir temperature at 18 to 22 C. Warm water holds less dissolved oxygen.
Flush before harvest
Most schedules run plain water for the last 7 to 14 days. Published trials on flushed versus unflushed cannabis show no consistent difference in tissue mineral content, so the flush is a labor and cost choice more than a quality step. Growers who skip it save water and time.