how high should i let ams grow before flowering

newbie on here 1st time growing ams, being just under 4 weeks now and they are about 17 cm tall, any advice much appreciated

Really depends on the strand that you are growing, but ultimately it is up to you. I put my plants into flowering when the one plant was 15 inches and pre flowers and the other one from the same bag was 25 inches with no pre flowers... Keep in mind that the plants are likely to double or maybe triple the size of that they were in Vege, and make sure they are over a foot tall before you consider putting them into flowering. What are you using for light and how many plants? Need much more information in order to give you decent advice, help us help you.

i got six plants in a growdobe with a biax 110 watt flourescent double lamp on them,with a small desk fan. as i say its my first grow so will probably upgrade to a better lighting system on the next grow....thanx 4 da help anyways i will learn how 2 upload a photo so ya can take a look, cheers ogkushoo !!!