When is tobacco harvested?

Once the leaves are yellow-green is the time when tobacco is harvested.

Specifically, color clues the harvester into the plant in question's ( Nicotianaspp) optimal maturity. The leaves have to yellow, a process which requires 80+ days from germination (or 60+ days from transplanting). They may be extracted from the bottom upward and the outside inward as each layer yellows in leaf harvesting, through cutting the base once the bottom- and top-most leaves yellow by a stalk harvesting, or with the passage of 3-5 weeks after the tobacco plant's terminal bud is removed in topping harvesting. Whatever the method, the harvesting must be done after the morning dew dries or once the sun's heat and light dim by the mid and late afternoon.