Cannabis Feeding Schedule — Week by Week
Pick one nutrient line and stick to it
The two most-used beginner lines are Biobizz (fully organic, very forgiving) and General Hydroponics Flora Trio (mineral, more control). Don't mix brands in a cycle. A cheap dosing syringe — not the bottle cap — is the difference between "1 ml/L" and a burned plant.
See nutrient lines on Amazon →Listen to the summary
Note (3 November 2026): this audio and the short version below were recorded in June 2026, before the 3 November 2026 correction, and still describe a 12-week Biobizz schedule with EC and pH per week. That Biobizz table has been removed; follow the official Biobizz schedule linked in Schedule A. A new recording will follow.
The Short Version
A good feeding schedule isn't a mystery — it's a table. Which bottle, at what dose, at what EC, at what pH, per week. This article gives you the full 12-week schedule for the two most-used nutrient lines (Biobizz organic and GH Flora Trio), plus when to add Cal-Mag, enzymes, and bloom boosters.
First: how to use this schedule
The schedule is a starting point, not dogma. Every plant, water source, and strain reacts differently. The table gets you to ~85% optimal — the last 15% you calibrate via runoff EC and how the leaves look (see pH and EC + nitrogen deficiency).
No measuring protocol = no feeding schedule. For every watering: measure EC + pH of what you give, measure EC + pH of the runoff. Adjust on the difference. For the EC side you need an EC meter; our Bluelab Truncheon review covers one.
Watch this first
Official General Hydroponics how-to
The official GH demo. The Flora Trio schedule below follows these doses — watch how to combine the three bottles safely.
Schedule A — Biobizz (fully organic)
The Biobizz bottles: Bio·Grow, Bio·Bloom, Top·Max and Root·Juice, plus others in the official schedule. Biobizz kits on Amazon.
Correction (3 November 2026): an earlier version of this section gave a 12-week Biobizz table with doses, EC and pH per week and NPK figures. That table had no source and does not match Biobizz’s own chart, so we removed it. Use the official Biobizz nutrient schedule (dated 3 August 2026, read 3 November 2026), which has separate tables for All·Mix and for Light·Mix or Coco·Mix, in ml per litre of water. It gives doses only, no EC or pH targets. Our Dutch page Biobizz voedingsschema reproduces both tables. Two rules from that schedule: Bio·Grow and Fish·Mix do the same job, so use one or the other, not both, and switch to Bio·Grow for flowering; for hard water Biobizz points to Bio·Down, for soft or RO water to CalMag.
Schedule B — General Hydroponics Flora Trio
Flora Trio uses three mineral bottles you combine. More intensive, but more control than organic. FloraMicro (micronutrients, always add first), FloraGro (veg macros, nitrogen-heavy), FloraBloom (bloom macros, phosphorus + potassium-heavy). The ratio shifts per phase:
| Week | Phase | FloraMicro | FloraGro | FloraBloom | EC total |
|---|---|---|---|---|---|
| 1–2 | Seedling | 0.5 ml/L | 0.5 ml/L | 0.25 ml/L | 0.8 |
| 3–4 | Early veg | 1.5 ml/L | 1.5 ml/L | 0.5 ml/L | 1.2 |
| 5–6 | Late veg | 2.5 ml/L | 2.5 ml/L | 1 ml/L | 1.6 |
| 7 | Pre-bloom | 2.5 ml/L | 2 ml/L | 2 ml/L | 1.7 |
| 8–9 | Early bloom | 2.5 ml/L | 1 ml/L | 3 ml/L | 1.8 |
| 10–11 | Peak bloom | 2 ml/L | 0.5 ml/L | 4 ml/L | 2.0 |
| 12 | Flush | — | — | — | 0.0–0.4 |
Mixing order (crucial): FloraMicro FIRST into the water, stir, then FloraGro, then FloraBloom. Otherwise the salts crystallize and nutrients drop out of solution.
Additives — when and why
Cal-Mag (coco, and soft or RO water)
Coco substrate binds calcium. In coco: 1 ml/L Cal-Mag in every watering, all weeks. In soil: usually not needed — only add at the first sign of interveinal chlorosis (see magnesium deficiency). Cal-Mag on Amazon.
Enzymes (root health)
Break down dead root material and help prevent root rot. Use 1 ml/L from week 4 to week 11. Skip in seedling (too strong for young roots) and in flush.
Mycorrhizae (root fungus)
Add once at transplant to the final pot (week 3 or 4). Sprinkle 1–2 g into the transplant hole. Improves nutrient uptake for the plant's life. Works only with organic feeding, not mineral systems.
Bloom boosters (Top·Max / PK boosters)
Optional. We have not measured what they add, and we cite no source for a terpene or density gain. For Biobizz’s own Top·Max doses per week, see the official schedule linked above.
Common mistakes
- Following the schedule without measuring runoff. The schedule is an estimate; what the plant actually gets shows in the runoff water. Measure every watering.
- Ramping up too fast. A seedling on 2 ml/L in week 2 burns roots. Raise the dose 0.5 ml/L per week, no more.
- Dosing by eyeball. A ml/L is a ml/L. Buy a cheap dosing syringe — not the bottle cap.
- Not re-checking pH after feeding. Nutrients always lower pH. Measure pH AFTER mixing, not before.
- Mixing brands. Stick to ONE nutrient line per cycle. Biobizz + GH bottles together have unpredictable buffers.
Adjustments by situation
Autoflower strains
Whole schedule at 70–80% of the doses above. Autoflowers have less root mass and accept less feed. EC also 0.2–0.4 lower.
Coco instead of soil
Coco doesn't buffer — every watering must contain feed. Cal-Mag mandatory. Doses stay the same, frequency higher (daily vs every 2 days). See the coco guide.
DWC / NFT (true hydroponics)
EC 0.2–0.3 lower than substrate values. pH 5.5–6.0 instead of 5.8–6.2. Replace reservoir water fully every 7–10 days — don't just top up. See hydroponics for beginners.
Bottom line
A good feeding schedule is a table + daily EC/pH measuring + a willingness to deviate based on what the plant does. Follow the table above for your first 1–2 cycles; from cycle 3 you'll start noticing your strain wants a little more Bio·Grow in week 4, or that a booster only kicks in for you around week 10.
FAQ
When should I start feeding cannabis seedlings? Day 10-14 from sprout, when the first true leaves (3-fingered) are fully formed. Before that: only pH-corrected water — seedling cotyledons supply enough nutrients for ~10 days. Starting too early causes nutrient burn before the root system is large enough to handle it. First feed: 25-30% of the bottle's recommended veg dose. Watch for tip-burn over 48-72h; if any appears, scale back.
How much do I water + feed during early vs late flower? Volume rule: water until 10-15% runoff out the bottom every 1-3 days in soil/coco, daily or twice-daily in hydro. Concentration rule: ramp UP from week 1 (EC 1.4) to week 6 (EC 2.0-2.2), then ramp DOWN from week 7 onward. Many growers make the mistake of holding peak EC through harvest — bud taste suffers and trichome maturation slows. Late-flower (week 8+): EC drops to 1.4-1.6, then flush week 11-12 with water-only.
Should I follow the bottle dosage or use less? Almost always use less. Nutrient manufacturers print maximum doses to cover all strains, all mediums, all stages. Real-world starting point: 50-60% of label dose, then ramp up by 0.2 EC every 5-7 days only if runoff-EC stays below 2.0 and no burn appears. The aggressive "Lucas Formula" type schedules (GHE Flora Trio, Advanced Nutrients) assume strong genetics + ideal climate + experienced grower — none of which describes a first-cycle indoor hobbyist.
Do I need flushing the last 2 weeks of flower? Mixed evidence. Organic soil (BioBizz All-Mix): no, the microbes break down nutrients gradually so the buds aren't carrying free salts at harvest. Coco/hydro: yes, 7-14 day flush with water-only (EC <0.4) removes accumulated salts that affect taste. Test: chew a tiny bit of dried bud — if it tastes "chemical" or harsh, you under-flushed. If it tastes smooth and slightly sweet, your flush worked.
Why do my plants look hungry even though I'm feeding heavily? Three common causes: (1) pH lockout — feed EC is fine but pH is outside 5.8-6.8 range, locks specific nutrients out. (2) Salt buildup — runoff EC is >3.0 even though feed is 1.8, blocking root uptake. Solution: flush. (3) Wrong nutrient ratio — you're heavy on N (greens) but plants need more P/K mid-bloom. Test pH + runoff-EC first; only adjust feed amount after ruling out the first two.