If you've got plants in front of you right now and you're second-guessing your light intensity, humidity target, or whether it's time to flip — this cannabis grow chart is the reference you need on the wall above your tent. Every number here is stage-specific and actionable. No ranges so wide they're useless. No vague "adjust as needed." Just the data that drives consistent harvests.
Of the 1,000 grow journals tracked on Grow Guide, 732 are indoor grows — meaning most growers using this kind of reference are working in a tent or room where they control every variable. That's exactly where a grow chart pays off the most. Outdoor growers will find the environmental targets useful too, particularly for VPD and harvest timing.
What a Cannabis Grow Chart Actually Covers
A good cannabis grow chart is not just a pretty timeline poster. It's a multi-variable reference that tells you, for each growth stage:
- Light: photoperiod (hours) and intensity (PPFD in µmol/m²/s)
- Environment: temperature, relative humidity, and derived VPD
- Nutrition: EC (electrical conductivity) target and NPK emphasis
- Water/medium: pH target and feed frequency
- Duration: how many days to expect in each phase
Below is that full chart, broken into the five main phases. Use the Grow Schedule Planner to build a personalised calendar from these numbers.
The Full Cannabis Grow Chart by Stage
Stage 1 — Seedling Phase (Days 1–14)
Seedlings don't need much. Blast them with 600 µmol/m²/s and you'll stunt root development and cause bleaching. Keep PPFD at 100–300 µmol/m²/s, maintain 74–78°F, and run humidity at 60–80% to support transpiration through underdeveloped roots. Feed lightly — EC 0.4–0.8 mS/cm — or skip feeds entirely if you're in a pre-charged soil. For seedling-specific nutrition, see our guide on the best nutrients for cannabis seedlings.
pH in soil: 6.0–7.0 throughout all growing phases. The plant cycles through different micronutrient uptake windows across that range, so don't lock it to one number — alternate between 6.2 and 6.8 across waterings.
Stage 2 — Vegetative Phase (Days 14–70)
Veg length is a yield lever you control. Most indoor growers on Grow Guide run 21–42 days in veg, but if you're running a single-plant indoor grow, extending to 56 days with LST or ScrOG can double your canopy without increasing strain count.
Nutrient profile in veg: NPK emphasis on nitrogen, roughly a 3:1:2 ratio. EC should climb from 0.8 at the start of veg to 1.4–1.6 by the final week before flip. Run your Grow Light Calculator to confirm your light is hitting 400–600 µmol/m²/s evenly across the canopy — uneven PPFD in veg creates uneven stretch in flower.
VPD target in late veg: 1.0–1.2 kPa. This is where a lot of growers miss it — they watch temperature and humidity separately instead of combining them into VPD. At 80°F and 65% RH you're sitting at ~1.1 kPa. Drop that humidity to 50% and you're at ~1.6 kPa, pushing the plant into stress before it's even flowered. For canopy training approaches that work well in veg, see our Fimming vs Topping guide.
Cannabis Grow Chart: Flowering Phase Breakdown
Flower is where the cannabis grow chart earns its keep. Most nutrient errors, environmental mistakes, and harvest timing calls happen in the 7–9 weeks between flip and chop.
Nutrient Transitions in Flower
At flip, begin shifting from a 3:1:2 NPK toward a 1:3:2 ratio by week 3 of flower. Phosphorus and potassium drive calyx development and resin production; excess nitrogen at this point delays maturation and keeps foliage too green, delaying the visible fade that signals the plant is finishing. By week 7, back off nitrogen almost entirely. EC should taper from its flower peak (1.6–2.4 mS/cm) down to 0.4–0.8 in the final week if you're running a flush. Use the Nutrient Deficiency Identifier if you spot leaf yellowing that looks like something other than a natural late-flower fade.
Humidity Management in Late Flower
This is where grows get lost. Dense buds at high humidity — above 50% RH — are a Botrytis incubator. Target 35–50% RH from week 4 of flower onward. If you're running an outdoor or mixed environment and can't drop below 55%, increase airflow directly through the canopy and consider defoliating interior bud sites to improve air circulation. Of the 1,000 grows tracked on Grow Guide, soil was the medium in 633 of them — and soil growers in late flower are particularly prone to overwatering, which compounds humidity problems from the medium side.
How to Read Trichomes for Harvest Timing
The cannabis grow chart gives you day counts as a guide, not a harvest trigger. The real harvest signal comes from trichome colour under a 60–100x loupe or digital microscope:
- Clear trichomes: THC not yet fully developed. Too early.
- Cloudy/milky: peak THC, energetic effect. Start the harvest window.
- Amber: THC degrading to CBN, more sedative. Ideal mix: 50–70% cloudy, 20–30% amber for most indica-leaning cultivars.
Also check pistil colour: 70% of white pistils turned reddish-brown is a secondary indicator that you're inside the window. Don't use pistils as your sole signal — they respond to touch and environment. Trichomes don't lie. Harvest in the early morning before your lights come on to preserve terpene profiles that accumulate overnight. Explore how different cultivars express their terpene profiles post-harvest with the Terpene Explorer.
Cannabis Grow Chart: Dry and Cure Phase
Dry and cure is where most first-time growers give up gains they earned over three months. A fast dry at high temperature destroys terpenes and produces harsh smoke. Target a 10–14 day dry at 60–70°F with 55–65% RH in complete darkness. Hang whole branches if space allows — buds on stems dry more slowly and evenly than trimmed buds on screens.
The snap test: small stems (pencil-thickness) should snap clean, not bend. Larger stems can still flex slightly. Once dry, move into mason jars filled 75% full. In the first two weeks, open jars for 10–15 minutes daily — this burping releases CO₂ and residual moisture. After two weeks, burp three times per week. Add Boveda 62 packs to maintain jar RH at 58–62%. Use the Dry & Cure Timer to track your burping schedule and flag optimal jar-ready dates.
Minimum cure: 2–4 weeks. Serious quality: 8 weeks. The chlorophyll breakdown that happens in weeks 2–6 is responsible for that smooth, developed flavour that separates dispensary-grade bud from backyard trim.
Tracking Your Grow Against the Chart
A cannabis grow chart is only as useful as the data you compare it against. Keeping a structured grow journal — logging actual PPFD, EC, pH, temperature, and RH readings against these targets — is how you identify where your grows drift and what to fix next run. See our guide on keeping a cannabis grow diary for the full system.
Once you've got your target stage times locked in, plug them into the Grow Schedule Planner to build a week-by-week calendar with nutrient transition dates, environmental shift reminders, and harvest window projections. And when you're ready to estimate what your grow should yield based on your setup, run your numbers through the Yield Calculator.
Frequently Asked Questions
How long is the full cannabis grow cycle from seed to cured bud?
Expect 16–26 weeks total: 1–2 weeks seedling, 3–8 weeks veg, 7–10 weeks flower, 2 weeks dry, and a minimum 2–4 weeks cure. Faster autoflower strains can compress the growing phases to 9–12 weeks, but the dry and cure timeline is the same regardless of genetics.
What should EC be during the cannabis flowering stage?
Start early flower at 1.2–2.0 mS/cm, peak in mid-flower at 1.6–2.4 mS/cm, then taper to 0.4–0.8 in the final flush week. These targets are for soil; coco and hydro growers can run EC 10–15% higher due to faster throughput.
When do I flip to 12/12 for flowering?
Flip when your plant has reached roughly half of its intended final height — plants typically double to triple in height during the flowering stretch. For a 4-foot tent, flip at 18–24 inches of plant height. There's no minimum day count, but most indoor growers veg for at least 21 days to establish enough node sites for meaningful yield.
What humidity should I target in late flower to avoid bud rot?
Drop relative humidity to 35–50% from week 4 of flower onward. Botrytis (bud rot) thrives above 55% RH in dense colas — once it's in, it spreads fast and there's no recovery for affected buds. Increase airflow through the canopy if you can't reduce RH via a dehumidifier.
How do I know when drying is finished and it's time to start curing?
Snap a small stem (pencil thickness or thinner) — if it breaks cleanly with an audible snap rather than bending, the bud is ready to jar. If it bends or feels springy, give it 1–2 more days. Don't rush this; jarring buds that are still too wet leads to mould inside sealed containers.
References
- Clarke, R.C. & Merlin, M.D. (2016). Cannabis: Evolution and Ethnobotany. University of California Press. Foundational reference for cannabis plant biology and growth cycle physiology. ucpress.edu
- Caplan, D., Dixon, M., & Zheng, Y. (2017). Optimal Rate of Organic Fertilizer during the Vegetative-Stage for Cannabis Grown in Two Coir-Based Substrates. HortScience, 52(12), 1,683–1,689. Established EC and nutrient rate benchmarks for cannabis in coir. doi.org/10.21273/HORTSCI12243-17
- Rodriguez-Morrison, V., Llewellyn, D., & Zheng, Y. (2021). Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment. Frontiers in Plant Science, 12. Defines PPFD response curves across veg and flower stages used in modern grow charts. doi.org/10.3389/fpls.2021.646020
- Pellegrini, M., Fattorini, S., & D'Ercole, F. (2021). Cannabis sativa L. Drying Methodologies, Cannabinoids and Terpene Profiles. Plants, 10(12), 2709. Documents temperature and humidity effects on cannabinoid and terpene retention during the drying and curing phase. doi.org/10.3390/plants10122709
- Grow Guide Platform Data (2026). Aggregated anonymised grow journal data from 1,000 tracked cannabis grows, covering environment type, growing medium, and feeding method distributions. growguide.app.
