i dont see a reason to..... flush 2 weeks prior to harvest n your good. the plant essentially flushes herself. (moderately) she'll use what she wants, and leave the rest alone in the soil. then you come by and water again and.......... flush! it drains outsome people use a routine of water, water, nute, water, water, nute.... but it's your call on how you feed, just dont over do it