The cannabis life cycle from seed to seed

A seed and the seed it might eventually produce are the same organism at two ends of one arc, not two separate topics. Between them it germinates, builds a root and shoot system, grows vegetatively for as long as its grower allows, senses the nights lengthening or simply turns a set age, flowers, fades, and, only if pollen reaches a stigma, sets seed of its own. Most "life cycle" pages are really a week-by-week schedule wearing that title. This one stays at the level of the arc: what triggers each move, the decision you actually get to make at each transition, and how long the whole thing takes, before you go looking for week-by-week detail.

Use this table as the map. Each row is a transition, what actually causes it, the one decision it hands you, and the article that covers it properly.

Germination: the one stage the grower doesn't control

A viable seed needs water, oxygen and warmth, and nothing you do speeds up the chemistry much beyond getting those three right. Water enters the seed coat by imbibition within the first hour or so, reserves stored in the embryo start converting to usable sugars, and the radicle, the first root, breaks through the coat. Grower consensus puts the comfortable range at roughly 20–25 °C (68–77 °F), where a healthy seed usually shows a visible taproot within a few days to a week, with the whole process commonly finishing by day 10; slower seeds at the same temperature are usually still viable, just not vigorous. Treat that range as a safe default rather than a proven optimum: it's grower practice, not a figure this page could confirm against a controlled trial.

This is the one transition with no decision attached: you can pick the temperature and the medium, but you can't judge or improve a seed's internal readiness from the outside. That is also why germination sits outside the "which route should I choose" framing that runs through the rest of this page — there is no route here, only conditions.

Seedling establishment: small, fragile, running on stored energy

Once the cotyledons (the seed's own two starter leaves) open and turn green, the plant photosynthesises for the first time, but it is still living mostly off the seed's reserves until the first true, serrated leaves expand. This stage typically runs 10–21 days, grower practice rather than a figure from a controlled trial. The seedling has no real root mass yet, so it wilts fast if the medium dries and rots fast if it stays waterlogged — overwatering, not underwatering, is the more common failure here because a small seedling in a large pot rarely dries out between waterings.

The seedling becomes a vegetative plant by degree, not by a single event: watch for two to three pairs of true leaves and a stem that no longer needs staking, rather than a fixed day count.

Vegetative growth: the one stage that is entirely your call

Vegetative growth is where the plant builds the stem, branch and root architecture that everything downstream depends on — and it is the only stage in the whole arc where the length is a decision, not a biological fact. Left on a long photoperiod (16–24 hours of light), a photoperiod plant will simply keep vegetating; it stops only when the grower shortens the light, or, outdoors, when the calendar does it for them. Autoflowering plants are the exception: they move to flowering on internal timing regardless of light schedule, which removes this decision entirely (see photoperiod vs autoflower for how that trade-off plays out).

Two to eight weeks (14–56 days) covers most home and commercial choices, and some mother-plant and phenotype-selection programmes hold plants vegetative indefinitely. Every extra week of veg roughly means a bigger plant at the flip and more branches to support more flowering sites. It also means a taller finished plant, because photoperiod cultivars typically double or more in height during the stretch that follows the flip.

What actually flips the switch to flowering

For a photoperiod cultivar the trigger is night length crossing a threshold specific to that plant, not a fixed "12 hours"; the mechanism itself belongs to the photoperiodism explainer linked in the table above, so it isn't re-derived here. What matters for this page is how much that threshold moves around: a controlled study of 27 hemp cultivars found critical photoperiod thresholds ranging from about 13 h 45 min to over 15 h 30 min depending on cultivar, and four cultivars flowered even under a 24-hour photoperiod, effectively day-neutral ^[1]. A separate study of ten indoor high-THC cultivars found flowering still initiated at day lengths up to 14 h in every cultivar tested, and two of those cultivars showed yield and flower quality more than 35% higher under 13 h than under the conventional 12 h ^[2].

Autoflowering plants don't read the light schedule at all: they carry a recessive trait (the Autoflower1 locus) that makes flowering age-triggered instead of photoperiod-triggered, with flowering commonly starting around four to five weeks after planting under continuous or long-day light ^[3]. That is the entire mechanical difference behind the photoperiod-vs-autoflower choice linked above: one route hands you control over timing by letting you set veg length, the other hands you a fixed, shorter total in exchange for giving that control up. Outdoors, the same photoperiod biology means flowering starts when nights naturally lengthen past a cultivar's threshold after the summer solstice, with the specific dates shifting by latitude, which is its own topic in outdoor seasons by latitude.

The days right after the flip (or, for autoflower, right after the internal trigger) are the stretch: elongation continues even as the plant commits to flowering. In one controlled study tracking a single indoor cultivar node by node, the first visible inflorescences appeared 10 days into the short photoperiod, with flowering well under way by day 15 ^[4] — a useful anchor for the 10–15 day range most growers report, though it is one cultivar in one setting and other cultivars run longer or shorter.

This is also the window in which sex becomes visible on non-feminised plants, and where you decide what to do about it: pull males for flower production, or keep one back if you're planning to breed. That decision, and how to read the pre-flowers that reveal it, is the sexing how-to linked in the table above; choosing regular, feminised or autoflower seed is what determines whether you need to make it at all.

Why the same seed can take three months or five

Add the ranges above together and the spread is enormous, almost entirely because of one variable: how long you vegged. The figure below works three indoor scenarios from the same component ranges, plus one outdoor case, to show where the weeks actually go.

Seed to harvest, total time (days)

• Autoflowerage-triggered, ~10 weeks70 days
• Photoperiod indoor, 3-week vegtent-height limited117 days
• Photoperiod indoor, 8-week vegcanopy-fill, plant-count limited152 days
• Outdoor, Mediterranean latitudesown spring, harvested autumn165 days

1. Home, tent-constrained: pick a short veg≈ 117 days total

   Germination 7 days + seedling 14 days + a deliberately short 21-day veg to stay under the tent's height limit + transition 12 days + flowering and ripening 63 days = 117 days, about 16.7 weeks or just under four months.

2. Commercial, canopy-fill: pick a long veg≈ 152 days total

   Same germination, seedling, transition and flowering numbers, but veg runs 56 days to build fewer, bigger plants that fill a fixed canopy footprint under a plant-count limit. Total: 152 days, about 21.7 weeks or five months — five weeks longer than the home example above, purely from the veg decision.

Both totals sit inside the roughly three-to-five-month range that indoor photoperiod growing commonly spans; where you land in it is a room-and-schedule decision, worked through properly in the "how long a grow takes" article linked in the table above. Autoflower collapses that decision to roughly eight to twelve weeks total, because there's no veg length to choose ^[3]. Outdoors, the season sets both ends: sow or transplant after your last frost risk, and the plant flowers when nights lengthen past its threshold regardless of what you'd have chosen indoors. See the law section for whether outdoor growing is even permitted where you are before planning around it.

Flowering to senescence: the plant's own countdown

Flowering itself divides roughly into a bulking phase, where flower mass and trichome density build, and a ripening phase, where trichomes shift from clear to cloudy to amber and pistils darken from white to orange-brown. Those readiness cues are covered properly in the grow-stages section, not re-derived here. Senescence is the natural next step, not a separate failure: fan leaves lower in the canopy yellow first as the plant remobilises mobile nutrients like nitrogen out of ageing tissue and into the still-developing flowers, a normal reallocation rather than a deficiency to correct. In the last one to two weeks before harvest, that yellowing climbing the plant is one of the more reliable low-tech readiness signals available, alongside a trichome check. The full read on what it does and doesn't tell you is in senescence and the natural fade.

Left unharvested well past normal ripeness, some cultivars don't just fade quietly: in the same node-by-node study cited above, spontaneous male flowers appeared on an otherwise female plant 76 days (about eleven weeks) after the photoperiod flip, well beyond the point most growers would have harvested ^[4]. That's a different phenomenon from deliberate pollination below, but it's a real argument for not treating "just leave it and see" as a neutral choice once ripeness has passed.

If you let it go further: pollination and seed set

Everything above describes the route to harvested flower. Cannabis sativa is naturally dioecious and wind-pollinated: separate male and female plants, pollen carried on air currents rather than by insects ^[5]. Seed only forms if pollen actually reaches a receptive pistil, deliberately or otherwise. Pollinated flowers stop investing in the resin and flower mass a grower usually wants and start building seed instead: energy shifts to the developing embryo and seed coat, calyxes swell around the forming seed, and the surrounding flower's own ripening effectively pauses while that happens. Growers who breed deliberately therefore treat a pollinated branch, or a whole pollinated room, as a different, longer-running crop rather than a slightly later harvest of the same one; commonly reported windows put a seed from viable to physiologically mature at roughly four to eight weeks after pollination, though this varies enough by cultivar and conditions that it's worth confirming against your own plants rather than a fixed number.

None of the breeding decisions belong on this page: which plant to pollinate, how to collect and store pollen, how many seeds a real selection needs. They're covered properly starting with selecting males for a breeding programme in the genetics section. What belongs here is the hand-off itself: seed set is where this arc closes, one plant's life cycle becoming the start of the next one's, and, in every jurisdiction covered by this library, something only worth planning within whatever your local law actually permits for cultivation and propagation.