Autoflower vs. Photoperiod Cannabis Seeds
The most important decision when buying cannabis seeds isn't which strain you choose -- it's which flower timing fits your situation. Autoflower seeds flower automatically based on age and finish in 9 to 12 weeks from seed, no light schedule required. Photoperiod seeds flower in response to light and take longer, but give you more control over plant size and yield. Both produce quality results. The right one depends on how you're growing.
| Autoflower | Photoperiod | |
|---|---|---|
| Flowering trigger | Age (automatic) | Light schedule change |
| Time to harvest | 9 to 12 weeks from seed | 4 to 6 months from seed |
| Indoor light schedule | 18 to 20 hours, start to finish | Veg on 18/6, flower on 12/12 |
| Outdoor timing | Finish 9-12 weeks after germination | Finish in fall with shortening days |
| Plant size | Compact, 2 to 4 feet | Larger, 4 to 10+ feet outdoors |
| Yield per plant | Smaller | Larger |
| Multiple harvests | Yes, 2 to 3 per season outdoors | One harvest per season outdoors |
| Best for | New growers, small spaces, fast results | Experienced growers, larger yields, full expression of genetics |
Which One Is Right for You?
Choose Autoflower if you...
- Are growing cannabis for the first time
- Want to harvest in under 3 months
- Are growing outdoors in a short season climate
- Have limited indoor space
- Want multiple harvests per season outdoors
- Don't want to manage a light schedule change
Choose Photoperiod if you...
- Want larger plants and bigger yields per plant
- Are growing in a long season climate or greenhouse
- Want full control over when your plant flowers
- Are comfortable managing a light schedule indoors
- Want to run the genetics to their full potential
Not sure which climate you're in? Check the USDA Zone Map to find your frost dates and growing window. Or text us at (919) 410-6945 and we'll help you figure it out.
Frequently Asked Questions
Yes. Modern autoflower genetics have closed the gap significantly. The main difference is yield per plant, not quality. Autoflowers produce smaller plants with smaller harvests, but the cannabinoid and terpene profiles are comparable to photoperiod varieties at the same THC levels.
Technically yes, but you need a consistent light schedule to flower them properly. A timer is a $15 solution that removes all the guesswork. Without one, plants either won't flower or will re-veg if the light schedule isn't consistent. It's one of the first things to set up for an indoor photoperiod grow.
Full season strains take longer to finish outdoors and are best for climates with a long frost-free window, typically zones 7 and warmer. Short season strains start flowering about 4 weeks earlier, making them the right choice for growers in northern climates where fall arrives quickly. Use the USDA Zone Map to check your window before choosing.
You can, but it creates a conflict. Autoflowers prefer 18 to 20 hours of light throughout their entire life. Photoperiods need a switch to 12/12 to flower. Running both in the same space means one format will be on a suboptimal schedule. Most growers keep them in separate spaces or run one format at a time.
Yes, but less than photoperiods. Autoflowers are smaller plants with faster life cycles, so they don't need heavy feeding. Starting with a quality potting mix and supplementing lightly after week 4 or 5 covers most grows. Overfeeding is a more common mistake than underfeeding with autoflowers. See our fertilizer guide for specifics.
Most outdoor growers in the US can get 2 to 3 autoflower harvests between late spring and early fall. A plant started in May finishes by late July or August. You can start a second round immediately after. Use the outdoor planting timing guide to plan your season.
Not harder exactly, but they require more active management. You control when flowering starts, which means more decisions and a longer timeline. For an experienced grower that control is an advantage. For a first grow, the shorter timeline and automatic flowering of autoflowers tends to be more forgiving. See our guide for new growers if you're just getting started.
Yes. Cannabis seeds contain less than 0.3% THC and are federally legal to purchase under the 2018 Farm Bill. Triangle Seeds ships to all 50 states. Whether you can legally grow them depends on your state. Check our state home grow guides to see where your state stands.
