In general terms the plants should be ready after 8 weeks of bloom. You can tell they are getting ready when the majority of white hair on the buds starts to change colour (usually grey, sometimes red or purple). When around 80% of hair changes colour the plants are ready to be harvested. Quote from happygirl.ca grow guide.
^Sorry, wrong. The color of the hairs is not an accurate indication of when to harvest. For the most part flowering time is genetic and varies by strain, from a short end of about 7 weeks to the long end approaching 14 weeks. True that many strains fall into the 8-9 week range, but do not go by the calendar. (And all of these time windows begin when flowering starts, not when 12/12 lighting starts). Also do not go by the color of the hairs. The one true way to know is to check the trichomes under magnification, most growers harvest when 25-50% have turned amber. Get a cheap $10 pocket microscope from Radio Shack to check.
cheers Toasty... Trichioms are the only way to truly get the best out of your grow, Do what he said get the microscope I have two just in case...... I dont even watch the calender just makes me anxious... let them tell me when its time.... The reward is worth the wait..
i know this might sound like a stupid question... but all this time i thought that the Trichioms are the white hairs... so what and were are they exactly please??..
Finally someone who knows what they are talking about.. I humbly bow to your knowledge... But technically you can count the number of days you've been on 12/12 as flowering days since you aren't using them as a time line to harvest. the number of days you have been on 12/12 will just become for reference only, and when you harvest you will still have peak maturity of THC if you go by the crystals...personally 25%-50% amber is too much for me, I like the "laughing high" so I'm harvesting when I have 25% clear/75% cloudy which is around 7 weeks. so on Monday mines are getting chopped. (I'm still trying to find out who started this rumor that you start counting number of days flowering when actual flowers start to show on the plants. In botanics we call it the "Flowering season" which happens when the hours of daylight is shortened, causing the plants to start developing buds. So in the same sense, when you shorten the number of hours of light to what is required to induce the budding hormone, then you have began flowering, not at the first sight of buds/flowers...been like that since the beginning of time)