The invention relates to a method and apparatus for sorting plant material units (101), such as seedlings. The plant material units are arranged in a supply tray and distributed over a plurality of further trays, each further tray being dedicated to plant material units with a specific classification value assigned to it. In the method, first, the supply tray (105) is provided. An image of the plant material units in the supply tray is obtained, and on the basis of the obtained image, a classification value is assigned to each of the plant material units. Finally, the plant material units are sorted on the basis of the assigned classification value by transferring plant material units with the same assigned classification value by means of a robot directly from the supply tray to the corresponding further tray.