Abstract: In a swather formed by a tractor and attached heeder for cutting standing crop to form a swath, reel speed and optionally draper speed are controlled relative to ground speed by a control system including a manually operable input and display available to the operator. The control system can be used in an automatic mode to set an index value for an actual difference in reel speed relative to ground speed and to vary reel speed accordingly. In this mode a manually operable control varies the index. The control system can be switched by the operator to manual in which case the same control varies the actual reel speed. Minimum reel speed can be set by the same control and when operative the automatic system does not allow reel speed to fall below the minimum set value despite the values of index and ground speed.