how tall they should be before you flower depends on your avialable grow height. they will double to triple in size once you induce flowering. The amount of plants depends on the method of growth i.e. sog, SCrog, topping, fimming, lsting, or just letting it grow with minor pruning as needed. I just let my grow with some lower branch pruning and in my grow room is 3.5ft by 2ft by 7ft and I can fit up to six good size plants in there fine.
