late flowering question

For one, flushing works to remove fertilizers from inside the plant. Smoking less fertilizer can make for a somewhat healthier, smoother and more flavorful smoke. Secondly, washing away the ferts in the soil towards the end of flowering can also help prevent new growth from forming that won't have time to mature.

It's not a required procedure, though. You can still grow great buds without flushing but since it doesn't cost anything besides a few cents on your water bill, there usually isn't a downside to doing it.

 

No- watering and flushing are two different things. More precisely, flushing is watering but watering is not necessarily flushing. Watering only wets the soil and if you flush every time you water, you'll constantly be wasting any nutrients in the soil. Only flush at the end of flowering or when there's a known toxicity in the substrate.

To flush, you just run water through the substrate until all solubles are washed away. You can take the plants outside or to a garage with a drain in the floor and stick a hose in each one for awhile. Some people stick the plants in the shower but to do it that way, you should place a screen of some sort over the drain to catch debris.

Flushing should be performed on each plant in one sitting. If there are time constraints, you can completely flush half the plants one day and any remaining plants the next day. Some people flush many days in a row but doing so causes overwatering. All solubles in the substrate can easily be washed away by flushing once, if done properly. How long it takes depends on the substrate; how quickly water will flow through it. You'll want to keep going for at least twice the time it takes for the water to start coming out clear at the bottom. As long as you only flush on one day, you can't really flush too much and the plants will be fine.

The final flush is usually the last watering before harvest. Since you'll be wetting the soil as much as possible, and also because you'll be drying the plants after you harvest, they can go a little longer than a normal watering cycle between flushing and harvesting. A bare minimum might be as little as five days. Be sure to give the plants at least that long between flushing and harvesting. I typically flush about a week before harvest and that's the last water those plants ever get.