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Flushing
Definition: Flushing is the practice of giving cannabis plants only plain, pH-balanced water, or a mild clearing solution, for the final days or weeks before harvest instead of nutrient solution. Growers using mineral salt nutrients often flush for 1 to 2 weeks to reduce built-up salts in the medium. Its effect on final taste remains debated.
How Flushing works
The idea behind flushing is that a plant deprived of fresh nutrients will draw down what it has stored in its leaves, leaving cleaner-tasting buds that burn to a light gray ash. Many growers swear by it. Controlled evidence is thin, and at least one blind consumer taste test found no clear preference for flushed flower.
Typical flushing by medium
- Soil with bottled nutrients: plain water for the last 7 to 14 days.
- Coco and hydro: 5 to 7 days, since these media hold fewer reserves and respond faster.
- Living soil or amended organic soil: usually no flush at all, because plants take only what the soil food web releases.
Doing it well
Measure runoff EC at the start, then water to about 10 to 20 percent runoff and watch the reading fall. Expect fan leaves to yellow, which is a normal late-flower fade. If leaves crash early, more than two weeks before harvest, cut the flush shorter next time.
Whatever you believe about flavor, slow drying and a proper cure affect taste far more. A rushed dry ruins a perfectly flushed plant.