Most temporary grass leys in Wales either comprise a mix of rye grass (Lolium perenne) and white clover (Trifolium repens) or are a monoculture of a rye grass cultivar. These temporary keys tend to be used as part of an arable rotation, i.e. to give the soil a rest from cultivation once in every three or four years. The flora and fauna associated with an arable leys is usually very species-poor.