Nap

The lateral growth of a turfgrass. This can be due to either the growth habit of a grass, especially if it spreads by stolons; or where maintenance operations, especially mowing, are carried out in the same direction on a regular basis. Regular brushing a turf surface helps to reduce nap, especially during periods of low mowing activity. Other activities to reduce and prevent nap are to vary the direction of mowing on a routine basis, as well as regular scarification, verticutting and grooming. In the USA this term is called Grain.