unless you're using 100% organics, you need to flush. if you want your ash to turn white and be super smooth, you have to flush. i've read threads where people don't flush in 100% organics but I've run 100% organics and even then I still flushed. the last few weeks before the plant is ready for harvest, it slows down on its nutrient uptake. start flushing 2 weeks ahead of time and you'll be golden. i wait for my trichomes to turn 50% cloudy and 50% clear if its the first time I'm running a strain as a guide for when the plant is 2 weeks away from harvest. i harvest when there's about 25% amber. i've not flushed and the result was bud that smoldered, not smoked. it was very harsh too. yes you can let it cure a month to make it a bit smoother but why not flush it right and have it cured to the same point in 2 weeks? if you let the flushed bud sit for a month, it just gets better and better. things differ for everyone, but most people I know flush. when you flush, the plant releases its stored up nutes to dine on. if you're in soil, you want to flush with 3x the amount of water to the size pot. so if you're growing in a 3 gallon, flush with 9 gallons off the bat. i recommend the next day before your lights come on doing an additional amount of water to flush out more nutes. the plants release some of their nutes at night as well. you want the water to be clear basically when it runs off. i've flushed some bud for 3 - 5 weeks and some strains like it and other don't. i started flushing a space queen @ 4 weeks and ended up with the smoothest bud i've ever smoked. other strains don't like it, they require more nutes. you have to dial your strain in and over time you'll know exactly what it takes. hope this helps.