No you can flower whenever,depends on how big you want the plant to be when finished,most will double in size and stretch the first couple weeks of flower. I've used a light very similar to yours before and flowered a few plants,the yield didn't compare to hps or cob led or even my cfl grow but you will get a decent stash,and if your in the us then getting beans is fairly easy anymore,I don't know your exact situation but plenty of reliable America based seedbanks and the one here at the farm too. Good luck