How many plants do you have?

Usually if you have more than 8 plants and you are using a 1000 watt hps for flowering you want consider flowering when the plants reach 8-24 inches.. depending on how many plants you have..

8 plants, you could let them get as big as 20 inches before flowering...
16+ plants, and you want to flower when they are 8-12 inches tall..


Alhoa