The invention relates to a method for operating a harvesting machine for harvesting a harvest material in a field, at least one operating value for a working organ of the harvesting machine being determined depending on at least one plant property of the harvesting material. According to the invention, the plant property is imaged in a plant growth model, wherein said plant growth model models a development of the plant property over time and determines, for the period of the harvest, an anticipated value or an anticipated form of said plant property.
