Flowering Questions

How old does marijuana have to be to flower and whats the best age/height?

I like 14-18". Usually get 4-5 feet when done

Age: Regardless of photo-period the plant will not flower for ~4 nodes or so (did 12/12 from seed a few times playing with cfl's and none flowered until atleast 4 nodes. weird ones needed extra PK, pH fluctuation, drop in photo period etc.) with this said: the age/height matters entirely on your room set up.

but yeahr, i like ~12inches

I think to a degree, it depends on indica or sativa, average strain stretch, and yield wanted for the plant. Indicas stay shorter and don't stretch as much as sativas. Some sativas flowered at 1.5 feet can reach five ft. when finished, while there are indicas who may only get to 2 feet and change flowered from same height. Certain plants also start to greatly increase yield if vegged longer. Look into the specific strain you will be growing and look for others grow journals so you know what to expect from the strain, then you'll have a much better idea of ideal height for your environment and plants. I have 3 strains and all are flowered at different heights.