Short answer. A first indoor grow takes about 3–5 months from seed to jar. Set up and test the room for a week, germinate, run gentle light for 1–2 weeks of seedling, veg photoperiods for 3–6 weeks, flip to 12/12 and allow a 10–14 day transition before flower really starts, flower for 7–10 weeks while feeding through to the end, then dry slowly for 7–14 days and cure for at least 2–4 weeks. Grow one to four feminised plants. Write everything down.
Legal first. Home growing is legal only in some places, with plant limits and rules about visibility and security. Do the legal check before you grow before you buy anything.
This guide is the spine of the "Start here" series. Each phase links to the step-by-step guide for it, and from there to the deep article with the evidence.
What do you need for a first grow?
A first indoor grow needs a small set of generic equipment, nothing branded and nothing exotic. Buy for the space you have; see choosing your setup for budget tiers.
- [ ] A grow tent sized to your space: 60 x 60 cm (2 x 2 ft) for one or two plants, 120 x 120 cm (4 x 4 ft) for two to four
- [ ] One dimmable full-spectrum LED that can deliver about 600–900 µmol/m²/s over the tent footprint (lights for beginners)
- [ ] An inline exhaust fan with a carbon filter, plus one small clip or oscillating fan
- [ ] 11–19 L (3–5 gal) pots, fabric or plastic with drainage, and saucers
- [ ] Quality bagged potting mix, or buffered coco plus perlite (soil or coco)
- [ ] A pH meter or pen, pH 4 and 7 calibration buffers, and pH up and down
- [ ] An EC meter (needed for coco and hydro; very useful in soil)
- [ ] A thermo-hygrometer with min/max memory, ideally one that logs
- [ ] A mechanical or digital timer for the light
- [ ] A 60x jeweller's loupe or clip-on phone macro lens
- [ ] A base nutrient for your medium, a measuring syringe and a jug
- [ ] Soft plant ties or garden wire for training
- [ ] A grow journal: paper, a spreadsheet or a GenetixBay journal
- [ ] Seeds of a well-documented feminised line (reading a seed listing)
What does the whole grow look like, week by week?
The whole grow runs about 18–24 weeks for a photoperiod plant and 13–20 weeks for an autoflower, counting setup, drying and curing. The table is the timeline; treat the weeks as typical, not fixed, because cultivars differ.
| Week | Photoperiod plant | Autoflower plant | Light | Main job |
|---|---|---|---|---|
| 0 | Set up, run the room empty 48 h | Same | Test run | Log day and night temp and RH; fix the climate first |
| 1 | Germinate, plant out | Germinate straight into the final pot | 18/6, 150–300 µmol/m²/s | Keep the medium moist, not wet |
| 2–3 | Seedling | Seedling | 18/6, 200–400 | Tiny waterings; no feed in most bagged soils |
| 4–6 | Veg; pot up into the final pot | Early veg; start LST about week 3 | 18/6 (up to 24/0), 300–600 | Water by weight; start training |
| 7–8 | Late veg; flip at half the final height you can fit | Pre-flower and stretch | Photo: 12/12 from the flip; auto: 18/6 or 20/4 | Fill the canopy evenly |
| 9–10 | Transition: days 1–14 after the flip, stretch | Flower | Photo 12/12, 600–900 | Count days since flip; check for male flowers |
| 11–16 | Flower (day 1 of flower is about day 10–14 after the flip) | Flower and ripening; most finish weeks 10–14 | 600–900 | Lower RH; weekly pest check; feed through |
| 17–19 | Ripening; harvest by trichomes | (Already in the jar) | Keep the dark period dark | No flush; taper only N if you mix salts |
| +1–2 | Dry 7–14 days | Dry 7–14 days | Dark room | 15–21 °C, 55–62 % RH |
| +2–8 | Cure in jars | Cure in jars | Dark | Slow moisture decline |
The flip is not day 1 of flower. In controlled studies the first real pistil clusters at the top of the plant appeared about 8–14 days after short days began, around 13–14 days on average across 27 hemp cultivars and up to three weeks in slow ones [2][3]. That's why runs go "longer" than a breeder's stated flowering time: see the photoperiod grow calendar and the flip-to-flower transition.
How do you run a first grow, step by step?
Run a first grow as twelve plain steps. Each step names its guide; follow that guide for the detail.
- Check the law. Confirm home cultivation is legal where you live, the plant limit, and any rules on visibility, locks and smell. See the legal check.
- Choose your space and kit. Pick the tent size first, then size the light and fan to it. See choosing your setup and electrical and water safety.
- Choose your plant type and medium. For a first grow, a feminised photoperiod in soil is the most forgiving; an autoflower is faster but punishes setbacks. Compare soil, coco and DWC.
- Run the empty room for 48 hours. Log temperature and RH with lights on and off. Aim for 22–28 °C (72–82 °F) lights-on and no more than 6 °C (10 °F) cooler at night. See climate basics.
- Germinate. Keep seeds at 22–26 °C (72–79 °F), moist and dark; plant a cracked seed root-down 0.5–1 cm (¼–½ in) deep. See germinating seeds.
- Raise the seedling (weeks 1–3). Light at 150–300 µmol/m²/s for 18 h, RH 65–75 %, and only a small ring of water around the stem. Most seedling deaths are overwatering. See watering.
- Veg (photoperiods, 3–6 weeks). Raise light to 300–600 µmol/m²/s, pot up into the final pot when roots fill the small one, start feeding lightly, and begin training: bend and tie, tuck rather than pluck.
- Flip to 12/12. Do it when plants are about half the final height you can fit, because they commonly double in the stretch. Keep the dark period completely dark. Log the flip date. See the grow calendar.
- Watch the transition and confirm sex. Days 1–14 after the flip are stretch and transition. Check every plant for male flowers or herms and remove any that will shed pollen.
- Flower (7–10 weeks of flower). Light at 600–900 µmol/m²/s, RH 45–55 % falling to 40–50 % late, and a daily five-minute check. Feed at stage strength right to the end. Do not flush (see below).
- Harvest by trichomes. Look at the heads on the buds with a 60x loupe and cut at a mix of a few clear, mostly cloudy, some amber. See when to harvest.
- Dry, then cure. Dry whole branches in the dark at 15–21 °C (60–70 °F) and 55–62 % RH for 7–14 days until small stems snap, then cure in jars, letting the buds' moisture fall slowly over 2–8 weeks. See drying and curing.
What numbers should a beginner aim for?
A beginner should aim for the middle of each range below and keep it steady; stability matters more than hitting an exact number. These are Grower practice ranges anchored to the cited studies; your cultivar may differ.
| Parameter | Seedling | Veg | Flower | Late flower |
|---|---|---|---|---|
| PPFD (µmol/m²/s) | 150–300 | 300–600 | 600–900 | 600–900 |
| Photoperiod | 18/6 | 18/6 to 24/0 | 12/12 or 13/11 (photos) | Same |
| Air temperature, lights on | 24–27 °C (75–81 °F) | 22–28 °C (72–82 °F) | 20–26 °C (68–79 °F) | 20–24 °C (68–75 °F) |
| RH | 65–75 % | 55–70 % | 45–55 % | 40–50 % |
| VPD (kPa, leaf) | 0.4–0.8 | 0.8–1.2 | 1.0–1.5 | 1.2–1.5 |
| pH, soil / coco and hydro | 6.2–6.8 / 5.8–6.2 | Same | Same | Same |
| Feed EC (mS/cm, coco) | 0.4–0.8 | 1.0–1.8 | 1.6–2.2 | 1.6–2.2 (taper N only) |
Yield rose roughly linearly with light up to about 1,800 µmol/m²/s in the best indoor trial [1], but a beginner gains more from steady, moderate light than from chasing the ceiling.
Should you flush before harvest?
No. Pre-harvest flushing is a Myth in the GenetixBay evidence ladder, and a harmful one. Cutting off nutrients in the last 1–2 weeks starves the plant while it is packing on most of its final weight, trichomes and resin. Controlled trials found no improvement in quality from pre-harvest nutrient withdrawal [6][9]. Cannabis stores what it takes up in its tissue, and plain water at the end does not wash it out.
What to do instead: keep feeding at the strength the stage calls for until harvest. If you mix single salts, taper only nitrogen over the last few weeks while keeping P, K, Ca, Mg, S and the micronutrients fed; lower N can raise cannabinoid percentage while lowering total yield, a trade-off rather than a reason to flush [5]. The one valid flush is a root-zone flush to clear salt build-up, at any stage. The full evidence is in the flush debate and feeding basics.
How will you know it's working?
You'll know a first grow is working when the plant shows steady, even growth and your logs stay boring. Check these signs weekly:
- Seedling: the stem stays short and sturdy (not leaning or stretched), cotyledons stay green, and a new set of true leaves appears every 3–5 days.
- Veg: a new node every 2–4 days, leaves a mid to deep green held flat or slightly up, and the pot drying from heavy to light in 2–4 days.
- Transition: stretch of 50–150 % over 2–3 weeks, then white pistil clusters at the tips about 10–14 days after the flip.
- Flower: buds swell week on week, lower fan leaves yellow slowly in the last 2–3 weeks (normal), and the smell grows.
- Ripening: trichome heads turn from clear to mostly cloudy with some amber.
- Dry: small stems snap rather than bend after 7–14 days.
- Logs: temperature within about 3 °C (5 °F) of target and RH within about 5 points, day after day.
What mistakes do beginners make on a first grow?
Beginners mostly fail from too much care, not too little. The common ones:
- Watering on a schedule instead of by pot weight. Drowned roots look like hunger, which tempts more feeding.
- Feeding full label strength from week one. Start at a quarter to half strength and work up by EC and plant response.
- Lights too close or too strong for a seedling, especially strong LEDs: bleached tops, upward-cupped leaves.
- Counting the flip as day 1 of flower and harvesting 10–14 days early.
- Flushing for the last 1–2 weeks "for taste". It costs yield and resin and gains nothing.
- Harvesting by pistil colour or by the calendar instead of by trichomes.
- Drying fast and warm. A hay smell from a rushed dry never cures out.
- Transplanting an autoflower. Plant autos straight into the final pot.
- Changing three things at once when something looks wrong. Change one, log it, wait 3–5 days and judge on new growth (how to diagnose any problem).
- Skipping the journal. Without dates and readings, the next grow repeats this one's mistakes.
Evidence
- Light and yield indoors: Supported by a cannabis-specific trial [1].
- The 10–14 day transition after the flip: Supported by controlled flowering studies [2][3]; the house position counts both days since flip and days of flower.
- Organic feed rates in coir veg: Supported [4].
- Nitrogen trade-off: Supported [5]. Pre-harvest flushing: Myth [6][9].
- Drying to aw 0.55–0.65: Established as a standard [7]; the drying climate is Grower practice.
- Mould and hygiene risks in humid flower rooms: Established [8].
