Hey Richard, haven't heard that expression in a long time!! When I used to use inorganic notes, I'd start flushing with plain ph'd water around 2 weeks before harvest. It kinda comes down to a part art/part science/part educated guess/part experience/part personal preference thing. For example, the finishing times listed on seed bank websites is just an average ballpark figure, but you might want to harvest early for higher THC % or later for less.
Visual clues like the white pistils have mostly turned brown and turning back in on themselves will be a sign they are getting close enough to start flushing. But best to check the resin glands up close with a little hand held microscope to get an idea of what percentage of amber colored glands you see. As the plant ages, more resin glands will turn brown as the THC converts to other compounds.
In example, if I want to end up with around 25% amber resin, I'd start flushing when I could see maybe 5% or so. Some growers will want to see more amber or less of course depending on their preference, or even to some degree the strain that is being grown. So, essentially, there is no "one size fits all" answer as there are just too many variables.
Having said all that, my recommendation for junior growers is just start flushing when you see mostly cloudy glands with a few amber colored glands here and there. Then later after it's dried and had a while to cure, sample some. Is it smooth or kinda harsh? How's the flavour? Is the result what you want? This is how experience is gained and lessons are learned, just be sure to keep notes as that is a big help.
In my case, since I grow organically, I'm not concerned with flushing at all. But I do usually stop giving nitrogen by the 2nd week of flowering and no food or water for the last week before harvest and that seems to work fine. Since I'm looking for a balanced effect for chronic pain management and still functional during daytime, my harvest time may be different than what you might be interested in. For insomnia, I would chose a later harvest time or perhaps a different strain geared towards that effect.
Basically it comes down to personal preference.....couchlocked and feeling no pain or higher than a hawks ass and ready to go bar hoppin' ?
