wait a few weeks, you want there to be enough vegetation so that you get atleast somewhat of a decent yield. from germination, id say wait atleast 3+ weeks - by then it would prolly be around the size of a plant for sea of green. its all about how much you wanna yield, if you flower after 1-2 weeks of germ youll prolly get a few g's - not even an 8th under your 170watts..but if you wait a few more weeks for it to develop some branches and bush out a little bit then your yield will increase.