There are two types of “flush” popular with cannabis growers. To “flush” before harvest means to stop giving nutrients at the end of a plant’s life so it has time to use up all the nutrients before harvest. The other type of “flush”involves
putting lots of water through a hand-watered plant that is sick from nutrient or pH problems. Giving lots of water helps flush out any nutrient buildup or other unwanted stuff in the grow medium, though plants often get droopyafterward.