How many weeks does it take to flower?

I am currently growing outdoors in the uk, I have forced flowering by bringing the plants into the shed for 12 hours a day. The only chemical I am currently using is Green Sensation Top Activator. The strain is uk cheese. This is my first grow, I just sort of want a rough idea of how many weeks this should roughly take. I am on the 3rd week at the moment, and the cola is forming very well and overall beginning to look like buds, although still mainly just hair.
Is there any advice anyone can give me here? Like should I be using other chemicals? Is trimming fan leaves a good idea? I would just like a rough idea of how many weeks it should take to be ready, I would like mor thc other than cb.
Thanks, Marc

just use some fowering nutes now, and from the start of flowering it will be around 8 weeks, could be more or less based on the strain, if u want more thc then when ur almost ready for harvest keep a close eye on the trichomes, get a 30x scope, and harvest when the trichs are cloudy, a few amber here and there wouldnt hurt

Thank you hopefully not too long for my babies then

Mr.Marijuana420 said:

just use some fowering nutes now, and from the start of flowering it will be around 8 weeks, could be more or less based on the strain, if u want more thc then when ur almost ready for harvest keep a close eye on the trichomes, get a 30x scope, and harvest when the trichs are cloudy, a few amber here and there wouldnt hurt

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Good answer, I agree!