Mowing is the periodic cutting of leaf blades. Turves are mown by mechanical rotary, reel, or flail mowers, or hand scythe. Grass leaf blades elongate from the base thus are adapted to such repetitive defoliation. Most other plants, dicotyledonous (broadleaf) plants especially, do not survive frequent defoliation. Mowing, grazing by animals, and fire act similarly to shift plant communities to domination by grass. To maintain sufficient photosynthetic area, grasses should not be mown more than 1/3 of their vertical height at any cutting. Optimum mowing frequency and height are determined by the 1/3 rule. To conform to this, low height lawns and sporting areas are cut frequently, while taller lawns and rights-of-ways are cut infrequently.

Husqvama auto mower 450 xThe reel mower was invented by Edwin Budding in 1830, based on textile finishing machines in the early Industrial Revolution. The reel mower has a cylindrical assembly of spiral steel blades attached to and rotating on a horizontal axis, the “reel.” The rotating blades slice against a fixed bedknife to cut grass leaf blades like scissors. The cut is sharp. In contrast, the rotary mower typically has one or more flattish or beveled blades rotating on a vertical spindle. The rotary mower does not technically cut grass leaf blades but shatters them. As a result of this less efficient action, and aerodynamic propulsion of cut leaf blades or “clippings,” rotary mowers are energetically costly (Fluck and Busey, 1988). Mowers are powered by gasoline, electricity, humans, and animals. There are many adaptations of mowers including hover mowers, filament mowers, and robotic mowers.