Just wanted to chime in on this thread. I've got a couple decades of growing under my belt and I still know very little.
IMO flushing is something I'd never go with out. Now before anyone jumps on me let me bring a little clarity. I only use GH flora series in my garden and nothing else. I don't go with the bottles recommendations tho I tone it down a little, less is more as "they" say. So here's real world, this week's experience...as I've also been going hard on flush research. The last week before water I cut my already lowered nutes solution by 1/3 with water over the last three regular feedings getting down to just water by the fourth feeding. After letting the plant use the "First" regular watering (about three days in 5 gallons of soil ) I brought each plant to my slop sink and put 5 gallons of clean water through each plant being as thsee were my final weeks. After returning my babies to there comfortable room I let them have a week before giving them another 5 gallons each. As a side note at this time I clipped a smaller side nug and set it on its way to drying so I could test it's cleanliness, meanwhile the plants continued under regular lighting for the week using the excess water up over 5 rather then 7 days this time. So now two weeks of just water, I take my scope in and check some trichs. It's a mix of plenty, cloudy and amber, I'm excited to see them and decide that my little sample is ready to test... (only a week I know but only a burn test )..so I chop, roll and light. It burns ok, what I would describe as a medium grey ash, not dark but def not white. So I decide to put 5 more gallons thru each. Also took another sampler as they plants now have two full weeks of just water. The plants now have dried after the third 5 gallon flush. The sample has also dried and been sampled
it burnt better but not to that high quality white ash I'm used to and like. So I took the scope in again and not only have the amber trichs become the prominent ones at around 40 % amber but there are abut 20% of the trichs that have turned purple and the rest are high majority cloudy with very few clear trichs to be seen. I haven't tested the plant yet but I'm certain it's ready. It's gping to be about ten days before I'll try a sample but it's my experience so far that yes flushing (in my case with my specific conditions of temp, water quality, humidity, pH, nutes mix etc etc) is important and that patience is key. All of that (sorry it is a chunk to read) being said, it really is a case by case issue son what worked and works for Tom might not be right or work for Dick or Harry. So that's my basic two cents on the matter, I'll include a cple pics of the ladies and the purple trichs (pic taken with a point and shoot thru a pocket scope so please excuse the poorer quality) for all to view, cheers, hope some of my experience helps. Where I live geographically every single grower I know from closet to commercial all do a two week flush, I've been doing three for ever and always had rave reviews. Pic #1 is pineapple express three weeks from finish. Pic two will be pk (the one with purple trichs) and the last one will be a shot of the trichs.
As a last note I find bong & pipe people don't really notice as much if the flowers are dirty / unflushed because they burn it directly with a lighter so unless it's really noticeable many (in my area) don't notice at all. I always do a test burn of any product I'm going to smoke by rolling a joint and burning it. If it urns clean you can see it by the way it burns (obviously ) and by the color of the ashes to some extent. Black, hard ash that won't stay burning is a sign you need more water. I'm always looking for a clean burning light grey towards white ash., cheers all.