Be patient,if you harvest early you'll kick yourself later.Barely gets you high if you smoke good bud all the time.
They flower according to the light cycle so as the days get shorter they start to flower more and more...some strains lag at first but catch up fast...also sometimes the flowers will stop growing for a little while ...if it does this don't worry it's just becoming more potent and resinous and will finish nicly.
Good Luck