Pilosella aurantiaca (orange hawkweed).

Abstract P. aurantiaca is a perennial herb which has spread rapidly in North America after its introduction as an ornamental and/or the contamination of pasture seeds from its native range in Europe. Although it is known to be a noxious weed elsewhere, it continues to be available as a garden ornamental and is therefore likely to spread further. It is an undesirable invader on account of its competitiveness, prolific seed production and vigorous vegetative growth leading to a drastic change in vegetation, loss in forage for stock, and loss of biodiversity. All Hieracium/Pilosella species are prohibited entry to Australia and New Zealand, and in the USA, P. aurantiaca is a declared weed in Colorado, Idaho, Minnesota and Washington.