Oh i get it now, sorry Dr i just didn't explain my question properly but Anti cleared up most of the questions i had only thing i wanted to be sure of is how tall do you start flowering them. 3" is that from the base of the soil or another measurement? hope i come across clear this time... I'm new to this whole indoor growing plus it's compact so i'm just trying to gather up all the info i can first.
My plants were flowered at day 31 from seed. So they had one full month to go from being a little bean sprout to being full-fledged plants. There is FULL documentation of my grow from the design of my cab, to the build of my cab, to the germination of seeds all the way through to today (near 1st harvest) with pictures every week or sometimes more, if you need visual aids.
To do things Dr. Bud's way, what you're going to need to do is to grow a plant from seed until it can show you that it's definitely female. Once you definitely have a female, you can start taking cuttings of that female and rooting those cuttings so that you have identical genetic copies of that one plant. Now you will begin to experiment with finding the correct plant height in your veg cab so that when you place it into flowering it will only grow JUST tall enough. To do this, you're going to start one clone on 12/12 when it's 2" tall.. you're going to start a second clone (of the same plant) on 12/12 when it's 3" tall. You're going to start a 3rd one at 4", a 4th at 5" and a fifth at 6" (all from the same plant.)
THen you're going to allow them to grow like normal and observe their final height. Whichever one grows to the PERFECT height in your cab (which is, basically, all the way up to within a few inches of the lights and then stop) is the "perfect" starter height for flowering for THAT STRAIN!
So at that point, you'll know that you need to grow strain x to a size of y in order for it to make maximum use of your headroom. Following all this? If you grow a different kind of plant from seed, it will not necessarily stop at the right height. You'd need to do the same exact kind of test on that new strain to find THAT strain's "sweet spot".
On average, plants will double or triple in size when you switch them to 12/12. So if for example you had 3ft of vertical space, you'd want to switch to flower by the time the plant was 12 inches tall.
I'm not on that step yet in my cab. I'm still on the first step, which is grow some plants out to find which ones I like enough to keep around. I'll be harvesting soon and I plan to reveg my plants and start my clone-farming once those plants have started to regrow limbs.