HUGE plants need huge root space. Digging a hole more wide than deep would help. Maybe about 2-3feet deep and 3-4 feet wide. what always helps is vegging a clone or mother and taking it outside when its older and bigger at the beginning of your growing season so it continues to veg for a lil while longer. A lot also has to depend on stain. If im not mistaken thats Jack the rippen in the pic by TGA seeds which is suppost to do pretty well outside. and a lot has to do on your climate and growing season.