Its strain dependant, grow style dependant, humidity dependant etc etc, from first sign to opening can be 3 days to a week, once starting to show they are programmed to open quickly to pollinate as many as they can, if im collecting pollen, I chop the male with its sacks still closed and leave to dry on a sheet of dark paper, the sacks will open naturally as it dries and the pollen falls out of the sack onto the paper.