Getting your nutrient schedule for cannabis right is the single biggest variable you control after environment. Light and airflow set the ceiling — nutrients determine whether you hit it. Based on Grow Guide platform data from over 1,000 tracked grows, 63% of growers are running soil, 15% coco coir, and the vast majority (55%) are hand-feeding on a manual schedule. That means most of you are mixing nutes by hand every watering, and the margin for error is real. This guide gives you the exact numbers to dial it in, stage by stage, medium by medium — plus the equipment you need to do it properly.
What Equipment Do You Actually Need?
Before we get into the schedule itself, let's talk about the tools that make the schedule executable. A nutrient schedule on paper is useless if you can't measure what you're putting into the plant.
Must-Have Gear (No Compromises)
- pH meter: A digital pen-style meter, not strips. Apera PH20 (~$40) is the budget benchmark. Bluelab pH Pen (~$80) is the step-up. Calibrate weekly with 4.0 and 7.0 buffer solution.
- EC/TDS meter: Measures nutrient concentration in your feed water. Apera EC20 (~$35) or the Bluelab Truncheon (~$65) for hands-off reliability. EC is more useful than TDS — make sure your meter reads in EC (mS/cm).
- Digital scales (0.1g precision): For measuring dry nutrients or precise liquid doses. Any kitchen scale in the $15–25 range works.
- Measuring syringes (1ml, 5ml, 20ml): Cheap, essential, and eliminates eyeballing liquid nutes.
- pH up and pH down solutions: GH pH Up/Down is the standard. Buy both — you'll use pH down far more often.
Worth Having (Speeds Up Troubleshooting)
- Runoff EC and pH meter: Checking runoff after watering tells you what's actually happening at the root zone. A $35 combo meter handles this.
- Refractometer (Brix): Measures sugar content in plant sap — useful for mid-to-late flower to confirm plant health.
- Nutrient reservoir (5–20L): Mix your feed solution in bulk, let it aerate 15–20 minutes before feeding. Any food-grade bucket works.
Premium Automation (For Serious Setups)
- Dosatron or Bluelab Dosetronic: Inline dosing systems that automatically mix concentrated nutrients into your water line. Accurate to ±2% and dramatically reduce feed prep time.
- Bluelab Guardian Monitor: Continuous pH/EC/temp monitoring with alerts. ~$300 but pays for itself in one avoided lockout event.
- Automated drain-to-waste systems: Timers + drip emitters. 12.6% of growers on Grow Guide already run top-feed drain-to-waste — it's the most scalable manual upgrade.
The Nutrient Schedule for Cannabis, Stage by Stage
Use the Grow Schedule Planner to map this directly onto your plant's calendar. The week numbers below assume a photoperiod strain with a standard 8-week veg and 8–9 week flower. Auto-flowering strains compress this — typically 5–6 weeks total veg before flower begins automatically.
Weeks 1–2: Seedling Stage — Feed Nothing
Cotyledons contain enough energy to push the seedling through its first two weeks. Your tap water's natural mineral content (typically 0.1–0.2 EC) is sufficient. Adding nutrients now risks burning fine root hairs before they're established. If you're in a pre-amended soil like Fox Farm Ocean Forest, you especially don't need to add anything — those mixes run 0.8–1.2 EC out of the bag.
Target: plain pH-adjusted water. Soil: 6.2–6.5. Coco: 5.8–6.0. EC: 0.1–0.3 max.
→ See our guide on best nutrients for cannabis seedlings for the exact moment to introduce your first feed.
Weeks 3–8: Vegetative Stage — Ramp Up Nitrogen
This is the growth window. Cannabis is building its structural framework — stems, fan leaves, nodes — and it needs nitrogen to do it. A high-N, moderate-P, moderate-K ratio is your target. Think 3-1-2 or similar NPK ratios (e.g., General Hydroponics FloraSeries Grow, or Canna Vega).
- Weeks 3–4: Start at 50% of label strength. EC target: 0.8–1.2 mS/cm in soil, 1.0–1.4 in coco.
- Weeks 5–6: Increase to 75% strength. EC target: 1.2–1.6 (soil), 1.4–1.8 (coco/hydro).
- Weeks 7–8: Full strength. EC target: 1.6–2.0 (soil), 1.8–2.4 (coco/hydro).
Check runoff EC at every other watering. If your runoff EC is climbing more than 0.3 above your feed EC, you have salt buildup — flush with plain pH water until runoff EC drops within range.
Weeks 9–16: Flowering Stage — Shift to P and K
Flip your lights to 12/12 (for photoperiod strains) and flip your nutrient profile at the same time. Nitrogen drops, phosphorus and potassium climb. This supports root development, bud site formation, and dense flower structure.
- Early flower (Weeks 9–12): Bloom feed at 75% strength. Look for 1-3-2 or similar NPK (e.g., Canna Flores, GH FloraBloom). EC target: 1.6–2.0 across mediums.
- Mid flower (Weeks 11–13): Add a PK booster (e.g., Canna PK 13/14, Aptus Topbooster). Use for 1–2 weeks max — these are concentrated and easy to overdo. EC can push to 2.0–2.4 in coco.
- Late flower (Weeks 13–16): Return to base bloom feed only, full strength. Begin watching trichomes. At 70–80% milky trichomes, you're entering your harvest window.
If you're seeing tip burn (necrotic leaf edges, brown crispy tips), you've hit nutrient burn. Drop EC by 15–20% and don't push it back up. Use the Nutrient Deficiency Identifier to distinguish burn from a true deficiency — the symptoms can look similar.
Final 1–2 Weeks: Flush
Flush with plain pH-adjusted water only. In soil: 1–2 weeks of plain water. In coco or hydro: 3–5 days is typically sufficient due to lower buffering capacity. Target runoff EC under 0.5 before harvest. This step improves flavor and smoke quality — residual salts in the bud affect the burn and taste noticeably.
Nutrient Schedule for Cannabis: Choosing Your Nutrient Line
The schedule above works with any complete nutrient line. Here's how the main options compare:
Synthetic (Salt-Based) Nutrients
Fast-acting, precise, and pH-stable when used correctly. Best for coco and hydro. General Hydroponics FloraSeries (3-part), Canna Coco A+B, and Dutch Pro are all reliable. Cost: roughly $0.10–0.25 per litre of feed solution. Downside: less forgiving — salt buildup happens faster.
Organic Nutrients
Slower to act but builds a living soil ecosystem. Better for soil grows. Bio Bizz, Roots Organics, and Vegamatrix are the main players. A growing number of growers in 2026 are moving toward fully veganic nutrients (no animal-derived inputs) — early data suggests improved terpene expression, though yields are comparable to standard organics. See our best organic nutrients for cannabis guide for specific products and dosing.
Two-Part vs Three-Part vs One-Part Systems
- One-part: Easiest. One bottle per stage (grow, bloom). Works for beginners. Less flexibility.
- Two-part: A+B systems (like Canna). Good balance of simplicity and control.
- Three-part: Micro/Grow/Bloom (like GH FloraSeries). Most control, steeper learning curve. Best for experienced growers dialling in a specific cultivar.
Troubleshooting Your Nutrient Feed
Nutrient Burn
Brown, crispy leaf tips that feel dry — usually starts at the very tip of the blade. Reduce EC by 15–20% at the next feeding. Don't flush unless EC is severely elevated (above 3.0 in soil). Just back off and watch the new growth.
Nutrient Lockout
When pH drifts out of range, nutrients become chemically unavailable even if they're in your feed water. Calcium and magnesium lock out below pH 5.8 in coco. Iron locks out above pH 7.0. Always check pH first before assuming a deficiency — use the Nutrient Deficiency Identifier to match your symptoms to the likely cause.
CalMag
If you're running RO water or soft tap water (below 0.2 EC), add calcium-magnesium supplement at 1–2ml/L from seedling stage onward. Coco coir is naturally calcium-hungry — always supplement CalMag in coco regardless of your tap water quality.
After the Feed: Dry and Cure
Your nutrient schedule doesn't end at harvest — it influences it. A proper flush means cleaner burning, better-tasting buds. Once you cut, hang trimmed branches in a dark room at 18–22°C (65–72°F) with 45–55% relative humidity. Expect 7–14 days to dry to the right moisture level (stems should snap, not bend). Then into glass jars for cure — burp daily for the first two weeks, weekly after that.
Use the Dry & Cure Timer to track your drying and burping schedule precisely, and the Yield Calculator to estimate your final dried weight based on plant count and grow style.
Want to plan the full grow from seed to harvest? The Grow Schedule Planner lets you plug in your strain's expected flowering time and auto-generates a week-by-week nutrient and environment schedule you can follow from day one.
Frequently Asked Questions
What EC should I feed cannabis in veg vs flower?
In vegetative stage, target 0.8–2.0 EC (mS/cm) depending on week and medium — start low at 50% strength and ramp up. In flower, push to 1.6–2.4 EC at peak, then drop back to base bloom feed in the final weeks. Coco and hydro tolerate slightly higher EC than soil.
How often should I feed cannabis nutrients?
In soil, water when the top 2–3cm of medium is dry — typically every 2–3 days in veg, daily or near-daily in late flower. In coco, you can feed daily or twice daily once roots are established. Never let coco fully dry out — it locks out calcium immediately when dry.
Should I flush cannabis before harvest?
Yes — for synthetic nutrient grows especially. Run plain pH-adjusted water for the final 1–2 weeks in soil (3–5 days in coco/hydro) until runoff EC drops below 0.5. This removes accumulated salts and noticeably improves smoke quality and flavor.
What pH should my cannabis nutrient solution be?
For soil grows, maintain feed water at pH 6.0–6.8 (sweet spot is 6.2–6.5). For coco coir and hydro, keep pH at 5.5–6.5 (optimal range 5.8–6.2). Always pH adjust after adding nutrients — nutrients change the pH of your water.
Can I use the same nutrient schedule for autoflowers?
Yes, but compress the timeline. Autos typically spend 3–5 weeks in veg before automatically flipping to flower. Start nutrients a week earlier (around week 2–3), and use lighter EC values throughout — autos are generally more sensitive to nutrient intensity than photoperiod strains. A max EC of 1.8–2.0 is a safer ceiling.
