Vertical mowing, or verticutting, is a maintenance practice periodically performed to accomplish the following: Remove excessive thatch and leaf biomass that contribute to puffy, spongy surface conditions. Improve mowing quality and surface smoothness. Cut laterally growing stolons and rhizomes to help promote a more upright growth habit of the turf, i.e., control turf grain. Create open grooves in the turf canopy for the incorporation of sand topdressing. Dislodge and remove Poa annua seedheads. The process involves using a putting green mower fitted with thin, tightly-spaced rotating blades that cut vertically into the turf. The depth of the blades is typically adjusted 1/64-inch to 1/8-inch below the mowing height so that the vertical blades penetrate and cut slits into the turf canopy. The goal is to thin the turf canopy while maintaining a proper balance of leaf growth and turf density. There is no standard recommendation for the frequency of vertical mowing. It is a judgment call made by the superintendent and course officials based on existing conditions and growth rate of the turf. Poa annua and creeping bentgrass greens tend to grow more rapidly during the spring and fall, while bermudagrass and seashore paspalum grow most actively in the summer. During these times, vertical mowing is often performed every two to three weeks, or even weekly. Vertical mowing is suspended during periods of turfgrass stress and/or limited growth. Caution must be exercised because excessive vertical mowing or doing so at the wrong time can damage greens and predispose the turf to infestations from fungal diseases, moss and algae.