on the 5 to 6 noddle you should top it , when u see the 5 or 6 noddle growing you should cut it right on you see a little funil inside the caule on a concave shape , you should see 4 black points separeted on the midle of the caule after cut it ( i dont know how to speak in english) but you shoul leave +- 15% off the apicial gema