Autoflower seeds are cannabis seeds that grow into plants which start flowering on their own after a few weeks, with no change to the light schedule. A photoperiod plant waits for 12 hours of darkness before it flowers. An autoflower ignores the clock and flowers on age. That one difference changes pot size, light timing, feeding, and how much room you have for mistakes.
Autoflower Seed Bank Recommendations: US Buyer Guide
Where the autoflower trait comes from
Autoflowering traces back to Cannabis ruderalis, a tough, short-season plant from Central Asia and Siberia. Breeders crossed it with photoperiod indicas and sativas, then worked those lines until the auto trait held steady in every seed. The trait is recessive, which is why the first autoflowers were small and low in THC. Modern breeding has closed most of that gap, and a good auto today looks nothing like the little shrubs from 15 years ago.
autoflower seeds for outdoor grow
Autoflower vs photoperiod: the practical differences
- Light schedule: autos run on 18/6 or 20/4 from sprout to harvest. Photoperiods need 12/12 to trigger flower.
- Life cycle: autos finish in roughly 8 to 10 weeks from sprout for most strains. Photoperiods run as long as you keep them in veg.
- Size: autos stay compact, often 1 to 3 feet indoors. That makes them easy to fit in a small tent.
- Cloning: not practical. An auto is on a timer from day one, so a clone has no time to root and veg before it flowers. You grow autos from seed each run.
- Transplanting: start them in the final pot. Autos stall if you disturb the roots.
What you actually get: yield, potency, and speed
Expect 1 to 4 ounces per plant indoors in decent conditions. Good modern autos test in the 18 to 24 percent THC range, and some hit higher. Yields per plant are lower than a long-veg photoperiod, but you can run more plants and harvest more often. Four autos in a 4x4 on 20/4 will outproduce a single big photoperiod plant over a year, and you get a harvest every couple of months instead of twice a year.
Autoflower Seeds Grow Tips: Light, Pots, Feed, Harvest
How I'd grow a pack of autoflower seeds
- Plant directly into a 3 to 5 gallon fabric pot of light, airy soil. Skip the solo cup.
- Keep temps around 70 to 80 F and humidity near 60 to 70 percent for the first few weeks.
- Run 18/6 or 20/4 the whole way through. More light hours mean more growth, within reason.
- Start bloom nutrients when you see pistils, usually around week 3 to 5. Go easy on nitrogen.
- Water less than you think. Let the top inch of soil dry out between waterings.
- Harvest when trichomes are mostly cloudy with a little amber, often 60 to 80 days after sprout.
Mistakes that cost people grams
- Starting in a small pot and transplanting later.
- Topping or training hard after week 3, when the plant has already started to flower.
- Heavy defoliation during the stretch.
- Running 12/12 out of habit and wasting light.
- Overwatering in the first two weeks, which is the most common way autos get stunted.
- Expecting a photoperiod-sized plant. Autos are compact by design.
Who should buy autoflower seeds
Autos suit beginners, small tents, short outdoor seasons, and anyone who wants a fast turnaround or a steady harvest cycle. They are also a good fit if you only grow from seed and don't want to manage a mother plant. They are a poor fit if you chase maximum yield per plant, like to keep clones, or enjoy a long veg. If you are shopping in a legal market, check the breeder and the stated seed-to-harvest window before you buy, because those two details tell you more than the strain name.