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.
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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.
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 you need: Bio·Grow (veg, NPK 8-2-6), Bio·Bloom (bloom, NPK 2-7-4), Top·Max (late-bloom stimulator), Root·Juice (root stimulator, first 4 weeks). Biobizz kits on Amazon.
| Week | Phase | Bio·Grow | Bio·Bloom | Top·Max | Root·Juice | EC | pH |
|---|---|---|---|---|---|---|---|
| 1 | Seedling | — | — | — | 1 ml/L | 0.6–1.0 | 5.8–6.2 |
| 2 | Seedling | 0.5 ml/L | — | — | 1 ml/L | 0.8–1.1 | 5.8–6.2 |
| 3 | Early veg | 1.5 ml/L | — | — | 1 ml/L | 1.0–1.4 | 5.8–6.2 |
| 4 | Veg | 2.5 ml/L | — | — | 1 ml/L | 1.2–1.6 | 5.8–6.2 |
| 5 | Late veg | 3 ml/L | — | — | — | 1.4–1.7 | 5.8–6.2 |
| 6 | Pre-bloom | 2 ml/L | 1 ml/L | — | — | 1.5–1.8 | 5.8–6.3 |
| 7 | Early bloom | 1 ml/L | 2 ml/L | — | — | 1.6–1.9 | 5.8–6.3 |
| 8 | Bloom | — | 2.5 ml/L | 2 ml/L | — | 1.7–2.0 | 5.8–6.3 |
| 9 | Peak bloom | — | 3 ml/L | 3 ml/L | — | 1.8–2.1 | 6.0–6.4 |
| 10 | Peak bloom | — | 3 ml/L | 4 ml/L | — | 1.8–2.1 | 6.0–6.4 |
| 11 | Late bloom | — | 2 ml/L | 3 ml/L | — | 1.5–1.8 | 6.0–6.4 |
| 12 | Flush | — | — | — | — | 0.0–0.4 | 6.0–6.4 |
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 (mandatory in coco + hard tap 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)
Raise terpene production and bud density in weeks 9–11. Not needed for a good harvest, but they take "good" to "excellent." Example doses are in the Biobizz schedule 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.