A flow distributor apparatus for a vertical spreader operable for discharging a flow of straw or other crop residue in a sideward direction over a field, the flow distributor apparatus including a flow guide element, an adjusting mechanism, and a coupling connector connecting the flow guide element to the adjusting mechanism for controllable repositioning of the flow guide element relative to the spreader paddles. The flow guide element is disposed generally adjacent to the back plate of the spreader and intermediate the spreader paddles with an apex portion, laterally extending arm portions, and longitudinally extending crop residue flow surfaces, at least portions of which crop residue flow surfaces extend beneath the spreader paddles. The adjusting mechanism is operable to effect at least either vertical, horizontal, or rotational movement of the flow guide element relative to the spreader paddles to adjustably vary the clearances between the outer swept diameters of the spreader paddles and the crop residue flow surfaces to control the sidewardly outwardly discharge of crop residue from the spreader.