Grow Q&A: When To Start Flushing Pot Plants

Dear Dan, I grow outdoors near Seattle and just started getting sugar-coating. The plants are doing fine in my greenhouse—a nice sativa strain (my own blend of Hawaiian and something else that grew fabulous), plus no pests this year! They’re real beauties, but I don’t want to flush too soon or too late. How do I know when to start flushing? Do I flush as soon as I see trichomes, or as soon as they get milky (which is when to pick and harvest, it seems)? Or would that be flushing too late? – S&S

Dear S & S,
Knowing when to start flushing your plants with plain water instead of nutrient solution is very important—too soon and you might stifle yields by not packing on weight during the crucial middle stage of flowering, when essential-oil production is at its peak; too late and your buds will taste harsh and burn improperly.

The key to understanding when to start flushing is to know your plant’s natural harvest schedule. If you plan to harvest on October 15, then begin the flushing on October 1 or so. Two weeks is the perfect amount of time to flush outdoor pot, so knowing when your strain typically finishes is paramount. If your seeds are listed as 60-day flowering, you should start the flush 14 days prior to when the full budding period has ended. The trichomes should be well-formed and bulbous, but mostly clear; they will cloud up closer to harvest time.

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