Pilosella caespitosa (yellow hawkweed).

Abstract P. caespitosa is a stoloniferous rosette plant which has spread rapidly to exotic locations outside its native range, namely to North America after its introduction as a garden ornamental or contaminant of agricultural seed. It continues to be available as an ornamental and can be easily transported by machinery and as such is likely to spread further. P. caespitosa is an undesirable invader on account of its vigorous growth due to stolon, rhizome and adventitious root bud production and wind-dispersed seeds which are produced in high numbers. P. caespitosa displaces desirable pasture plants leading to loss of forage and biodiversity. Early infestations of P. caespitosa which are still very small may be difficult to spot since this weed occurs on upland pastures and forest meadows in parts of the USA, and it is a declared weed in the states of Idaho and Washington (USDA-NRCS, 2016).