Plants started from seed in late Feburary outdoors should not flower. Days are getting longer and the plants know this. Stress could possibly cause this but still not likely. Most likely due to genetics, (auto flower).
I'm in the southern hemisphere, so I'm trying to work out what time of year end of February is to you, end of winter for you I think.
Firstly I was talking about seedlings being put outdoors, as no guerilla grower plants out seeds, little sprouts are too at risk of being eaten by rodents, bugs, birds etc.
Guerilla growers put out 1 foot high seedlings or clones.
Even in your backyard, I wouldn't reccomend planting seeds directly in the soil, better to have them in small pots to start, which is what the op has done I think.
So when I talk about outdoor planting times, I'm talking about planting out a 8 inch or more seedling or clone in the ground or a big pot, as that is what just about everyone does.
Sure if you put a seed in the ground outdoors, it will take a week to pop the surface, for the first week it will be only about 3 cm high, so that's two weeks it will not be able to flower, and in that two weeks the days are getting longer, so maybe by the time it gets to about 6 inches tall and is old enough to flower then the days will be too long.
Depends on the strain.
The Afghani #1's from Sensi I put out last year, I put out about 10 days after the middle of spring, and they vegged for about three weeks and got to about 3 foot tall and then went fully into flower.
I think they would have stayed in flower and not revegged too, but I didn't get to see that as a ripper found them so I had to move them inside and finish them there.
Now Afghani #1 is not an autoflower, if you keep it under 24 hours light it will not flower, I know as I have had a clone mother of it going for over a year, and no sign of flowering.
It's just one of these strains that when it reaches a certain height it will start to flower even if the daylight hours are over 13. But as I said it wont flower under 24 hours of light.
But plants don't sense the days getting longer and stay in veg, they produce a flowering hormone in the dark hours, a hormone that is destroyed by light, and when they are in an environment where the flowering hormone can build up to a higher level than the daylight can destroy, due to the long nights and short days, then they will flower.
