How do you guys know when to start feeding the plant plain ph'd water (flushing)?
On this site they differentiate between "flush" (large amount of water to flush the soil of salts, nutrients that may have burned a plant, etc.) and "cleanse" (feeding plain water, ph'ed or not, to a plant 2 weeks before harvest.). I suppose if you wait too long you could employ both methods: start with a flush, even using one of the chemicals to expedite flush, like Botanicare's FloraKleen, then begin cleansing by feeding plain water for whatever time you have remaining.
But, the common recommendation here is to start cleansing (without flushing) 2 weeks before you anticipate harvesting. The challenge for new growers (like me) is to imagine what the plant will look like two weeks into the future.
Best thing to do is read these two stickies:
when to harvest, and
lifecycle of an AF. Then post photos of your plant along with info about strain, age, etc. More info the better. Interpret advice based upon what you read in those stickies.
Here is
my first grow. If you read that post, I was about 3 weeks away from cleansing. If you read the subsequent posts in that thread, you'll see more photos showing what the plant looked like when I approached cleansing and harvest. This might help you assess your timing.
These things probably depend greatly upon strain and personal preference (stoney or mind high?). For me, waiting that long was extremely counter-intuitive while I did it -- but proved to be nearly perfect. The buds packed on significant weight during those final weeks. The trics turned cloudy (and a few amber) coinciding with the condition of the plant (as described in the "when to harvest" sticky).
My second grow is 7-14 days away from harvest. Started cleanse a week ago. It feels a lot better to know what I'm looking at this time, what to expect, etc.