Your Cannabis Growing Guide: Start Here
Whether you have seedlings under a T5 or you're two weeks into flower under a 600W LED, this cannabis growing guide is built around the decisions you're making right now — not textbook theory. Of the 1,000 grow journals tracked on Grow Guide, 73.4% are indoor grows, 63.4% run soil, and 54.7% feed manually. The advice below is calibrated to that reality, with specific numbers for every stage so you're not guessing.
Step 1: Germination and Seedling Stage (Weeks 1–4)
Germination is simple but easy to overwater. Soak seeds in plain pH-neutral water (6.5) for 12–24 hours until a tail emerges, then transfer to a seedling plug or directly into moist soil. Keep temps at 75–80°F (24–27°C) and humidity between 65–70% RH. Light intensity at this stage should be low — 200–300 PPFD is plenty. A 24-hour light cycle is fine for the first week.
Seedlings need almost no nutrients for the first two weeks if you're in a quality potting mix. If you are feeding, stay below EC 0.4 and use a seedling-specific formula — see our Best Nutrients for Cannabis Seedlings guide for specific product breakdowns. Overfeeding at this stage is the number one cause of slow seedling development.
Step 2: Vegetative Growth — The Engine Room of Your Yield
Veg is where you build the structure that carries your flowers. Most indoor growers run 18/6 light cycle for 4–8 weeks. Your target environment: 70–82°F (21–28°C), 50–65% RH, VPD 0.8–1.0 kPa. Ramp PPFD from 400 at week 1 to 600–900 by mid-veg. Use our Grow Light Calculator to confirm your fixture is hitting those numbers at canopy height.
Nutrients in veg should be nitrogen-forward. A typical EC range for established veg plants in soil is 1.0–1.6 mS/cm. In coco, push to 1.4–1.8. pH should sit at 6.0–7.0 for soil and 5.8–6.2 for coco or hydro. Water when the top 1–2 inches of soil dry out, or on a consistent schedule in coco (daily or twice daily).
Training During Veg: Don't Skip This
Training during veg is the highest-leverage activity in this entire cannabis growing guide. Topping or FIMing once or twice, combined with LST, can double your canopy coverage without adding a single extra day. If you're running a SCROG net, fill it to 60–70% before flipping to 12/12 — plants will stretch another 30–50% in early flower. Read our Fimming vs Topping breakdown if you're unsure which approach suits your setup.
Step 3: Flipping to Flower (Weeks 8–18 Approximately)
Switch to 12/12 light cycle to trigger flowering in photoperiod strains. In the first two weeks of flower (the "stretch"), expect 30–50% height increase. Dial back nitrogen and ramp up phosphorus and potassium. A mid-flower feed in soil might look like: N-P-K ratio shifting from 3-1-2 in veg to 1-3-2 by week 4 of flower. EC can push to 1.8–2.4 in late flower depending on strain and medium.
Environment in flower: drop RH to 40–50% to reduce mildew risk, keep temps 68–79°F (20–26°C), and push PPFD to 900–1,100 at the canopy. If you're running supplemental CO₂ at 1,200–1,500 ppm, your plants can handle up to 1,500 PPFD before photosaturation. Without CO₂ supplementation, stick to 900–1,000 PPFD maximum. VPD in late flower should be 1.0–1.5 kPa. Use our Grow Schedule Planner to map out your full flower feeding and environmental timeline week by week.
Step 4: Nutrients — What Plants Actually Need
Cannabis has three macronutrient phases across a typical grow. The problem with most commercial nutrient schedules is they're written at 100% dose, which regularly causes nutrient burn. Start at 50–70% of recommended dose and adjust based on leaf colour and EC runoff.
- Seedling (weeks 1–3): Near-zero feeding. Let the medium do the work. If pale yellowing appears after week 2, introduce a quarter-strength balanced feed.
- Veg (weeks 4–8): Nitrogen-dominant. EC 1.0–1.6 in soil. Key micros: calcium, magnesium, iron. Cal-Mag is the most commonly needed supplement for indoor grows, especially under LED and in RO water.
- Flower (weeks 9–18): Shift to P/K-dominant. Drop nitrogen sharply at week 3 of flower or you'll get airy, leafy buds. Supplement silica through week 6 of flower for stronger cell walls and stress resistance.
- Flush / Pre-harvest (final 1–2 weeks): Stop nutrients. Feed only pH-adjusted water to clear residual salts. EC of runoff should drop to below 1.0 by harvest day. This improves the smoothness of the final smoke significantly.
If leaves start showing spots, clawing, or discolouration, run them through the Nutrient Deficiency Identifier before reaching for a product. Overfeeding a deficiency is the fastest way to make it worse. For organic feeding strategies, see our Best Organic Nutes for Cannabis guide.
Step 5: The Cannabis Growing Guide to Troubleshooting Problems
Most problems fall into four categories: environment, nutrients, pests, and disease. Here's how to triage each one fast.
Environment Issues
If leaves are clawing down and dark green, you're likely running too high nitrogen or too-high humidity causing transpiration issues. If tips are burning, check EC — runoff above 3.5 mS/cm in late flower signals salt build-up. Get a decent VPD chart on your wall and check it every time you walk into the tent.
Pests
Spider mites appear as tiny stippling on upper leaf surfaces; fungus gnats come from overwatering; thrips leave silver streaks. For all three, implement an IPM protocol before you have a problem: neem oil or spinosad sprays weekly in veg, predatory insects (Amblyseius cucumeris, Hypoaspis miles) in the grow medium from week 1. Stop foliar spraying by week 3 of flower.
Disease
Powdery mildew shows as white powder on upper leaf surfaces and thrives above 55% RH in temps under 75°F. If you catch it early in veg, a potassium bicarbonate spray (1 tsp per litre) applied every 3 days for two weeks will clear it. In flower, lower humidity aggressively and improve airflow — spray applications risk mould in dense buds.
Step 6: Harvest Timing — Reading Trichomes Correctly
Harvest is the most common place growers leave quality on the table. A 60x loupe is the minimum; a digital microscope is better. Here's the three-stage trichome read:
- Clear trichomes: Cannabinoids still developing. Do not harvest.
- Cloudy/milky trichomes: THC at peak. Effects will be more cerebral and energetic.
- Amber trichomes: THC degrading to CBN. Effects become more sedative and body-heavy.
For most strains, harvest when 50–70% of trichomes are cloudy and 10–30% are amber — this is the standard potency-plus-body balance window. Check the pistils too: 70–80% darkened and curled in is a useful secondary indicator. Don't rely on breeder-stated "flower time" alone; it's almost always optimistic by 1–2 weeks. Estimate your final yield at harvest using the Yield Calculator before you cut.
Step 7: Drying and Curing — Where the Quality Is Won or Lost
A technically perfect grow can be ruined in the dry room. Here are the non-negotiable parameters: hang whole branches or use drying racks in a dark room at 60–65°F (16–18°C) with 55–60% RH and gentle air circulation (fan on a wall, not blowing directly on buds). This slow dry preserves terpenes. A fast dry at high temps destroys them — you'll end up with harsh, flat-tasting cannabis regardless of genetics.
Drying takes 7–14 days. The ready test: bend a small stem. If it snaps cleanly, you're ready to jar. If it bends, give it more time. Do not rush this.
For curing, use wide-mouth glass mason jars filled to 70–75% capacity. Store in a cool, dark space at 60–65°F. For the first two weeks, "burp" jars twice daily for 10–15 minutes each session to release moisture and CO₂. After two weeks, drop to once daily, then every few days. The minimum cure for good smoke is 4 weeks. 6–8 weeks is where the terpene profile really opens up. Use our Dry & Cure Timer to track burping schedules and target moisture content.
Keeping a Grow Journal: Why It Pays Off
Every number in this cannabis growing guide — PPFD, EC, VPD, trichome timing — only becomes useful if you record it. Growers who log systematically can cross-reference what went wrong, replicate what went right, and shave weeks off future grows by having a real baseline. Our platform hosts over 1,000 grow journals, and the data from those grows feeds the benchmarks used throughout this guide. Start yours with our grow diary guide, or go straight to the complete 2026 diary framework for a structured template.
Want to run the numbers on what your setup should produce? The Cost Per Gram Calculator turns your electricity spend, yield, and consumables into a real cost-efficiency metric — useful for tuning your setup over multiple grows.
Frequently Asked Questions
How long does it take to grow cannabis from seed to harvest?
Expect 14–20 weeks from germination to harvest day for most indoor photoperiod strains — typically 2–3 weeks seedling, 4–8 weeks veg, and 8–11 weeks flower. Add 7–14 days drying and a minimum 4 weeks curing, and the full seed-to-smoke timeline is 20–36 weeks. Autoflowers compress this to roughly 10–14 weeks seed to harvest.
What pH should I be targeting in soil vs. coco coir?
For soil, maintain a pH of 6.0–7.0 at the root zone, with 6.3–6.8 being the sweet spot for nutrient availability. In coco coir or hydro, tighten that range to 5.8–6.2. Swinging outside these windows locks out specific nutrients regardless of how much you feed.
When should I harvest — cloudy trichomes or amber?
Harvest when 50–70% of trichomes are cloudy/milky with 10–30% amber for the best balance of THC potency and body effect. Harvesting at all-cloudy gives a more cerebral, anxiety-prone high; waiting for 50%+ amber gives a heavier, more sedative effect as THC converts to CBN.
How often should I water cannabis plants in soil?
Water when the top 1–2 inches of soil are dry, or when the pot feels noticeably lighter — typically every 2–3 days in veg and every 1–2 days in flower as root mass and transpiration increase. Lift your pots dry and wet to calibrate by feel; it's more reliable than a calendar schedule.
How long should I cure cannabis for best results?
A minimum of 4 weeks in sealed glass jars produces noticeably better smoke than uncured bud. Six to eight weeks is where terpene complexity peaks. Beyond 8 weeks, keep jars 55–60°F in darkness and burp monthly — properly cured cannabis can hold quality for 12+ months.
References
- Wikipedia contributors. (2025). Cannabis cultivation. Wikipedia. Covers trichome harvest indicators and general cultivation biology. https://en.wikipedia.org/wiki/Cannabis_cultivation
- Grow Weed Easy. (2024). How to dry and cure cannabis. Practical drying parameters including the stem-snap test and 60–70°F / 50–60% RH dry room targets. https://www.growweedeasy.com/curing
- Distru Cannabis Blog. (2024). How to harvest a cannabis crop. Pre-harvest flush protocol and timing recommendations for commercial and home cultivation. https://www.distru.com/cannabis-blog/how-to-harvest-cannabis-crop
- Seed Supreme. (2024). When to harvest cannabis: ultimate guide. Curing timelines and jar-fill ratios for 4–8 week cure protocols. https://seedsupreme.com/blog/when-to-harvest-cannabis-ultimate-guide
- Grow Guide App. (2025). Cultivation techniques that actually boost yields. CO₂, temperature, and humidity ranges validated across indoor grow data. https://growguide.app/blog/greener-days-cultivation-techniques-that-actually-boost-yields/
