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Every grower eventually faces the same choice: photoperiod seeds, which flower when you tell them to, or autoflowering seeds, which flower on their own clock regardless of light schedule. The short answer: autoflowers are faster (8-10 weeks from seed), smaller and easier to get right; photoperiods take longer but give bigger yields, the highest potency and full control, including cloning. Neither is universally better. The right one depends on your space, your patience and what you want out of the harvest.
Autoflower vs photoperiod at a glance
| Autoflower | Photoperiod | |
|---|---|---|
| What triggers flowering | Age: 3-5 weeks after germination | Light: 12 hours of darkness (12/12 indoors, shorter days outdoors) |
| Seed to harvest | 8-10 weeks | 3+ months, depending on veg time |
| Yield indoors | Up to about 400-550 g/m² | Up to about 500-700 g/m² |
| Plant height | 60-100 cm indoors, 1-1.5 m outdoors | Often over 1.5 m; you control it with veg time and training |
| Potency | High; the top end still favours photoperiods | The highest THC ceiling |
| Light schedule | 18/6 or 20/4 from seed to harvest | 18/6 in veg, 12/12 in flower |
| Training | Low-stress training; topping is risky | All techniques: topping, FIM, SCROG, mainlining |
| Cloning | Not useful | Yes, and you can keep a mother plant |
| Room for mistakes | Little: no extra veg time to recover | A lot: keep the plant in veg until it recovers |
| Outdoor harvests | 2-3 per season | 1 per season |
| Best for | Beginners, small or discreet spaces, short summers, speed | Maximum yield, potency, cloning, experienced growers |
What are photoperiod seeds?
Photoperiod seeds grow into cannabis plants that start flowering when the nights get long. Most cannabis is a short-day plant: it only flowers once it gets about 12 hours of uninterrupted darkness. That’s photoperiodism, and it’s why photoperiod plants stay vegetative under roughly 18 hours of daily light and switch to flowering once you drop them to a 12/12 schedule, or once the days naturally shorten outdoors, typically in late summer in the Northern Hemisphere.
Photoperiod seeds can be feminized (all female plants) or regular (male and female). Most of the seeds sold today, including most of ours, are feminized photoperiods.
What does autoflower mean?
An autoflowering plant flowers automatically, based on age rather than light. Autos start flowering 3 to 5 weeks after germination, however much light they get. That trait comes from cannabis ruderalis. Centuries ago, cannabis spread from Central Asia into Russia and Siberia, close to the Arctic Circle, where summers are short and unpredictable. Plants that waited for shorter days to flower often didn’t mature in time. The ones that survived flowered on a fixed internal clock instead. In the early 2000s, breeders crossed ruderalis genetics into indica and sativa lines to create the first commercial autoflowering seeds. Two decades of breeding since then have closed most of the yield and potency gap that once made autos a compromise.
Autoflower vs feminized: these aren’t opposites. “Feminized” means the seeds grow into female plants; “autoflower” means the plants flower on age. Most autoflower seeds sold today are feminized too. We compare the two seed types in more detail in feminized vs autoflower yields.
Photoperiod: pros and cons
Where photoperiod wins:
- Yield potential. Since you control when flowering starts, you can extend the vegetative phase to build a bigger, more branched plant with more bud sites. A well-trained photoperiod plant indoors regularly produces 500-700 g/m². Strains like Caramba sit at the top of that range, and that ceiling still beats the best autoflowers.
- Full control over your timeline. A rough start, transplant stress, a pest problem or a heat spike doesn’t have to mean a lost grow. You can hold the plant in veg until it recovers, then switch to flowering when it’s ready.
- Cloneable and re-veggable. Find a phenotype with the structure, flavour or potency you want, and you can take cuttings to keep those exact genetics, or re-veg a harvested plant to run it again.
- Responds well to advanced training. FIM and topping, LST and HST, SCROG and lollipopping all work best on photoperiods, since the longer veg phase gives the plant time to recover before flowering.
- Higher THC ceiling. The most potent genetics available are still photoperiods.
Where photoperiod costs you:
- Time. With a proper veg phase, most photoperiod grows take 3+ months from seed to harvest. Even fast-flowering strains like Wappa or Mendocino Skunk, which can flower in under 10 weeks, still need veg time on top of that.
- Strict light discipline indoors. Any light leak during the dark period, a timer fault or a crack in the tent can stress the plant and, in the worst case, cause hermaphroditism. You need a light-tight space before you switch to 12/12.
- Judgment calls. Deciding when to switch takes experience: too early and you lose yield, too late and the plant outgrows your space.
- Space. Bigger plants mean more height, canopy and airflow to manage, which isn’t ideal if you’re growing somewhere discreet.
- Short outdoor seasons. In far northern latitudes, especially with sativa-leaning strains, photoperiods often won’t finish before autumn frost.
Autoflower: pros and cons
Where autoflower wins:
- Speed, regardless of season. Most modern autos are ready to harvest 8 to 10 weeks after germination. Strains like Vertigo or Pandora can finish in as little as 8 to 9 weeks.
- No light schedule to manage. Autos flower on age, not darkness, so light leaks, timer failures and schedule changes that would stress a photoperiod plant don’t matter. That makes them far more forgiving for a first grow or an improvised setup.
- Compact and discreet. Autoflowers typically stay at 60-100 cm in a tent and can reach 1-1.5 m outdoors with more room and light. Either way, they’re far easier to fit into a small space or keep out of sight.
- Multiple harvests a year outdoors. Stagger germination by 4 to 5 weeks and you can keep a rolling harvest going from June through October.
Where autoflower costs you:
- Lower yield ceiling per plant. The gap has narrowed a lot, but top autoflowers still typically cap at around 400-550 g/m², behind a well-trained photoperiod in the same space.
- Almost no margin for error early on. Flowering starts 3 to 5 weeks after germination no matter what, so early mistakes (overwatering, nutrient burn, transplant stress) go straight into your final yield. There’s no holding the plant in veg to let it recover.
- Can’t be cloned usefully. A cutting is the same age as the mother and starts flowering almost immediately. Every autoflower grow starts from fresh seed.
- Wants a lot of light. Autos reward 18-20 hours of light a day for the whole grow, so they don’t get the drop to 12/12 that cuts a photoperiod’s electricity use in flower.
Autoflower vs photoperiod yield
Photoperiods yield more, because you decide how big the plant gets before it flowers. Indoors, a well-trained photoperiod plant regularly produces 500-700 g/m², against around 400-550 g/m² for the best autoflowers. Per year, the picture is closer: autos finish in 8-10 weeks, so you can run more cycles in the same tent, or two or three harvests outdoors in one season.
Autoflower vs photoperiod potency
Modern autoflowers are strong, and for most growers the difference won’t be noticeable. At the very top end, though, the most potent cannabinoid and terpene profiles still come from photoperiod genetics.
Do autoflowers grow faster than photoperiods?
Yes. An autoflower goes from seed to harvest in about 8-10 weeks, with no separate veg phase to plan. A photoperiod needs a vegetative stage of a few weeks before you switch it to 12/12, plus 8-10 weeks or more of flowering.
Fast-flowering vs autoflower: fast-flowering (or “fast version”) strains are photoperiods bred to flower a week or two quicker. They still need 12 hours of darkness to start flowering, so you keep the control and yield of a photoperiod with a shorter finish. An autoflower ignores the light schedule completely. If you want speed without giving up control, a fast-flowering photoperiod is the middle ground.
Autoflower vs photoperiod outdoors
Outdoors, photoperiods follow the seasons: they grow through spring and early summer and flower when the days shorten in late summer, for one big harvest in autumn. That gives the largest plants and yields, but in a short northern summer they may not finish before the cold and wet weather arrives.
Autoflowers don’t care about day length, so you can sow them from late spring to midsummer and harvest 8-10 weeks later. That makes them ideal for short summers, balconies and discreet gardens, and for two or three harvests in one season. Our outdoor growing guide covers timing for both.
How to tell an autoflower from a photoperiod
- Check the seed pack or strain name. Autoflowers are almost always labelled “auto” or “autoflowering”.
- Watch the timing. Under 18 hours of light or more, a photoperiod stays in vegetative growth. A plant that shows pistils 3-5 weeks after germination, without any change in light, is an autoflower.
- Look at the size. Autos usually stay smaller and more compact, with fewer side branches by the time they start flowering.
Which should you choose?
Go autoflower if you’re growing for the first time and want one less thing to manage, you’re working with a small or discreet space, you’re in a northern climate with a short outdoor season, you want several harvests in one year outdoors, or speed matters more than the maximum possible yield.
Go photoperiod if you want the highest yield your space can support, you want to clone or keep a specific phenotype, you’re experienced enough to want full control over training and timing, potency is your top priority, or you’re running a perpetual harvest or mother-plant setup.
For beginners: autoflowers are usually the easier start, because the plant handles the timing for you. A forgiving photoperiod indoors is a good second grow, once you’re confident about light-tight spaces and veg time.
Grow with confidence either way
We’ve been breeding both photoperiod and autoflowering genetics in Amsterdam since 1994, and neither is the “better” seed type, just the better fit for a specific grow. Match the seed to your space, your timeline and your goals, and either will get you there.
Ready to pick your side? Browse our autoflower cannabis seeds for speed and simplicity, or our full seed collection if you’re chasing maximum yield with photoperiod genetics.