How We Make Hay Mowing The first stage is to cut the grass. This must be done when the grass is fully grown, but is not over-mature, so that it produces tough, stocky hay. It must also be cut when you think that you have 3 to 5 days of sunny weather to dry the hay. The grass is cut with a machine called a drum mower . Tedding The tedder takes the hay out of windrows, and spreads it flat across the field. Spreading out the grass just allows it to dry faster. Raking It usually takes 3 to 4 days for the hay to dry properly. The rake is used to rake the hay back into windrows, or to turn over the drying windrows. It is then ready to be picked up by the baler.