"Primers"" as they are referred to can be seen here harvesting tobacco. Harvesting refers to removing the mature ripe leaves from the plant. When the leaves begin to turn yellow, it is time to harvest them. Harvesting tobacco can be done by machine or by hand. These workers have chosen to do it by hand. Tobacco that is harvested by hand is either primed or stalk-cut. Bright-leaf tobacco that is hand harvested is primed. Priming involves picking leaves as they ripen. Leaves ripen and are harvested from the bottom of the stalk upward. Priming requires several harvests because the leaves ripen at different rates. Some growers use a pre-harvest chemical which causes yellowing of the leaves so more can be harvested at one time.