A self propelled walk behind mower including a tractor unit and a mowing deck. The tractor unit is hydrostatically driven with a unique control system whereby the forward speed of the tractor is set by operating an electric rocker switch with an operator's thumb. Hand levers are used to turn the tractor to the left and the right. The tractor unit comprises two drive wheels and a third wheel that is pivotally attached, letting the tractor unit stand upright when no implements are attached. Implements attach to the front of the tractor through a movable attachment so that the tractor and implement can closely follow the contour of the ground while keeping the operator controls in a convenient position.