I agree with lipps on the solutions, but I do, however, flush with water with 1tablespoon epsom salts to 1 gal water. Not to aid flushing, but to ensure the plants have enough magnesium. The smoke doesn't burn well if the plant was deficient in mag, & its ok to use as it leaves no metalic taste in the smoke. To flush with plain water with epsom (assuming your grow is in soil, not hydro), I fill the pot to the rim & let it run through 3 times. I do this 2 wks before harvest, then water as needed