Short answer. Seed, seedling, vegetative growth, transition, flowering, ripening, harvest. A photoperiod plant stays vegetative under long days (typically 18 h light indoors) and flowers once it gets long, uninterrupted nights (typically 12 h dark indoors). An autoflower flowers at a set age regardless of day length. Indoors, a photoperiod grow from seed usually takes 3-5 months; an autoflower 2.5-3.5 months.
What's happening
Cannabis is a short-day plant: what it actually measures is the length of the dark period. When nights pass a cultivar-specific threshold, the shoot tips switch from vegetative architecture to compact flower clusters [1][2]. Even under long days, plants of flowering age form solitary flowers at the nodes ("pre-flowers"), which is how you can sex plants before switching to 12/12 [1].
Stages and timing
| Stage | Typical duration (indoor) | What the plant is doing | Grower focus |
|---|---|---|---|
| Germination | 1-7 days | Radicle emerges, cotyledons open | Warmth 22-26 °C (72-79 °F), moist not wet |
| Seedling | 1-3 weeks | First true leaves (1, then 3, then 5 leaflets) | Gentle light, avoid overwatering |
| Vegetative | 2-8+ weeks (grower's choice for photoperiods) | Leaf, stem and root growth; nodes stack | Training, root volume, steady feeding |
| Transition / stretch | ~2-3 weeks after 12/12 | Stems can elongate 50-200% (genotype dependent); flower sites form | Height planning, canopy management |
| Flowering | ~7-12 weeks for most drug-type cultivars; 12-16+ for some tropical lines | Bract and stigma production, resin build-up | Stable climate, no light leaks |
| Ripening | Last 1-3 weeks of flower | Stigmas recede and darken; trichome heads turn cloudy, some amber | Decide harvest by trichomes and plan; keep feeding at stage strength (no pre-harvest flush: see the flush debate) |
| Harvest, dry, cure | Dry 7-14 days; cure 2-8+ weeks | Water leaves slowly; flavour and smoothness improve | ~18-21 °C (64-70 °F), ~55-62% RH for drying |
Durations are typical grower ranges, not laws (Grower practice). Breeders' stated flowering times are claims and often optimistic by 1-2 weeks.
The photoperiod threshold
The critical day length varies by cultivar. In a Florida study of 27 hemp cultivars, essential-oil types flowered 1-2 days later when days exceeded 13 h and a further 7-8 days later beyond 14 h; some had a critical day length of 13 h 45 min to 14 h. Very dim civil twilight (~2 µmol/m²/s) was enough to count as "light" for the plant [2]. Indoor growers use 12/12 because it reliably triggers essentially all photoperiod cultivars (Established practice).
Autoflowering is a different, genetically controlled pathway (a recessive locus, Autoflower1, in the populations mapped so far) [4]. See photoperiod vs autoflower.
Male versus female timelines
Males usually show sex earlier and open flowers sooner than females from the same seed lot. Males shed pollen within roughly 1-3 weeks of the switch; remove or isolate them before then unless you are making seed (Grower practice) [3].
Common mistakes
- Light leaks during the dark period. Even weak light can delay or disrupt flowering in sensitive cultivars [2].
- Vegging too long in a small space. Plan for the stretch: a plant can roughly double in height after the flip.
- Harvesting by the calendar instead of the plant.
Evidence
- Short-day (long-night) flowering and cultivar-specific critical photoperiods: Established [1][2].
- Pre-flowers under long days as sex indicators: Established [1].
- Stage durations above: Grower practice, highly cultivar dependent.
- Drying and curing ranges: Grower practice; see the harvest-cure category for evidence detail.
