Since 2002, the county flower for Derbyshire has been Jacob's-ladder ("Polemonium caeruleum"), a relatively rare species, and characteristic of certain limestone dales in the White Peak. Derbyshire is known to have contained 1,919 separate taxa of vascular plants (including species, hybrids and micro-species) since modern recording began, of which 1,133 are known to be either native or archaeophyte, the remainder being non-native species. These comprise 336 established species, 433 casuals and 17 unassigned. It is known that 34 species of plants once native here have been lost from Derbyshire (i.e. become locally extinct) since modern plant recording began in the 17th century. Derbyshire contains two endemic vascular plants, found nowhere else in the world: "Rubus durescens", occurring in central Derbyshire, and Derby hawkweed ("Hieracium naviense"), still known only from Winnats Pass. One endemic species of moss, Derbyshire Feather Moss, occurs in one small 3-metre patch in just one Derbyshire limestone dale, its sole world location intentionally kept confidential.