A Greensman or Greensperson or Greenskeeper is any production personnel on a film set who is responsible for obtaining and taking care of anything "green" – plants, grass, trees, flowers, and other various landscaping materials like rocks, gravel, sand, etc. Considered part of the art department.
This includes artificial forms of these materials up to and including those representing greens, such as camouflage netting.
Greens work is generally considered to be one of the dirtiest, most thankless, and physically demanding jobs in set construction. In addition to set construction greensmen often work "on set" assisting the camera and other departments in adjusting the set to the changing demands of different camera positions and lighting setups.
Ideally the greensman functions as a participant in the filmmaking process as an extension of the art department during set construction and in conjunction with the camera department during filming. The range of duties in this category ranges from tending to plant nursery operations (watering, fertilizing, transplanting, etc.) through to the artful crafting of vines, trees, flowers and the like using cut living material and various forms of artificial material.