Canadiananswered grow question 5 years ago The most technical and precise way to know is checking the trichomes with a magnifying glass 40X or higher but a more simple way will be looking at the bud and making sure there is no more white pistils shooting to the sky then look at those pistols and make sure they have all change colour red ,orange, brown, and they have curl down at that point you know your plant is ready to be harvested.
The benefit of using a microscope to check out directing the trichomes is that it give you a more control in what kind of high you want to get out of it more physical or cerebral .
Hope this information helps you out good luck with your garden