I never, NEVER like to give any advice about harvesting by any other method than trichome color and trichome color alone. BUT if you absolutely cannot get even a $12.00 from Radio Shack about as close as you can get to guessing right would be wait until 50%-80% of the white pistils (hairs) have turned dark (usually brown or red).
If you had a scope to look at them at about that time, depending of course on the genetics of the strain, you would find that roughly 10% of your trichomes would have turned amber, again depending on genetics and also the difference between 50% to 80% in pistil color change. If you gamble and wait much longer you risk losing THC.
　
If you end up harvesting a little early the maximum level of THC will not have been reached but you will get an increased amount of clear head high over if you harvest to late and then THC production has peaked but then began to degrade creating increased levels of CBN.
If the 50% to 80% pistil color change is accurate enough to keep you within the window of opportunity where THC production has just peaked and just before it is about to drop due to oxidation then you will be happy with what you got and did not lose anything at all.
　
The thing is if you would have amber trichomes they would show up on the tops first and that would likely mean the bottom portions would be all milky white/cloudy or at least turning milky white/cloudy so if you prefer more of a head high then you would want to pick a harvesting point closer to the 50% pistil color change time. Your colas are big producers and it you want your biggest best buds to give you a head high more than a couch-lock body stone then you don’t want to risk waiting until the trichomes on your colas turn amber.
　
If you want more of a couch-lock body stone then at around the 80% range you should have roughly 10% amber trichomes and they would be on the tops of your plants, your biggest best buds, and then those lower that will get smaller and fluffier as you go down your plants will give less of a couch-lock body stone and more of a head high but by not allowing the top trichomes to age longer you reduce the chance of increased levels of CBN due to the oxidation/degradation/loss of THC.
　
Most likely you will not get lucky and harvest at the prime time but you can decide if you want to risk less THC because the plant had not hit peak THC levels or instead risk less THC because the THC that did exist had by then degraded into CBN, a less desirable cannabinoid that makes someone feel confused and messed up instead of stoned or high and also when smoked it will make you feel like you are just about getting high/stoned and then that’s it, nothing more, nada, zilch. It teases you instead of pleases you.
　
But again, you have to decide for yourself.
