help! when to change to flowering light times?

my plants going to have been vegging for a month, i had a variety of seeds but im fairly sure its a durban poison
the plant has been nipped on the top once to prevent it being frail and its now starting to look good still not huge bout a foot and really bushy. ive hea of people downing the lights for flowering after only a couple of weeks can i do this yet or should i wait? ps hi im a newbie! and also started 2 lowrider2# seed today! really hope they work!

 

Have they shown any preflowers? I usually wait until then so I can be pretty sure what sex they will be.

 

i cant tell for sure yet, it looks as if its going to be a female but the preflowers dont give it away yet, also the lowryder2s have sprouted and are now in soil, an damn they wer quick i checked after 48hrs an the sprouts wer huge! anyone got any ides how i can cope with the lowryder2s and my vegging durban with one light? im in student housing i can only afford to grow in my cupboard!

 

dude.. the lowryders are an autoflowering strain, which mean you don't have to change the lighting conditions... they flower under any light cycle... so you can vegg your other seeds for as long as you like .. so you can just wait a little longer till the lowryders have given signs of flowering... and then switch to flowering light cycle...

 

Preflowers are poor indicators of sex. The only way you can tell FOR SURE is to wait until 2 weeks of flowering. By then the males will have grown balls (pollen sacs).

 

If you have vegged for a month, then wait 2 more weeks. That is if you have a decent amount of height to work with. Your plants can sometimes triple in height during flowering. Waiting a bit longer will only make things better, by increasing your yield. It all depends on what kind of time scale you are working with. And it also depends alot on the plants themselves.