Good information, will help a lot. They're about 1ft right now. Also, even if the plant only grows for a week or so during flowering, does root development also continue during flowering? Will i have to worry about transplanting once flowering has begun if the container currently is a "perfect fit" for the plant?
Mmm, Interesting questions and good ones too!
First off lets clarify something quick like. The plant DOES continue to "grow" throughout the flowering.....The major amount is done in the first few weeks for most strains but, Heavy Sativa's take a longer stretch period.. Indica's will about dbl in size in bloom, while Sativa's can even triple in size! Many crosses can fall in between the two.
In all growing, yes the roots will continue to grow in bloom but, at a very reduced rate the deeper it gets into bloom. Like on a bell curve, if you will.
I always did up potting as I saw need. The last up potting is done 8-10 days before the flip to flower. This gives the roots time to spread into the new soil and give space for them to fill as the flowering period continues. This is naturally for soil grows..
Never intentionally up pot during bloom! This is the BEST way to ensure root space and no "rooting stress" during bloom!
Now you know.
Good Luck
P.S. You should up pot the plants you have NOW! They are looking to be at that point in size relation to the pot their in....