Only once a season, starting in August and continuing through the fall. They let it grow as high as it wants or can, then knock it down late summer. Takes a while to cover the ski resort acreage, as its a real slow process dragging the mowing attachment behind a snowcat. The ground cover grows quickly this time of year, and seems to max out as high grasses, ferns, and wild flowers. That stuff goes dormant pretty fast after the first couple frosts/freezes at elevations in the early fall.