Orange hawkweed

Appearance

It is a low-growing plant with shallow fibrous roots and a basal rosette of elliptical to lanceolate leaves 5–20 cm long and 1–3 cm broad. All parts of the plant exude a milky juice. The flowering stem is usually leafless or with just one or two small leaves. The stem and leaves are covered with short stiff hairs, usually blackish in color. The stems may reach a height of 60 cm and have 2–25 capitula, each 1–2½ cm diameter, bundled together at the end of short pedicels. The flowers are orange, almost red, which is virtually invisible to bees, yet they also reflect ultraviolet light, increasing their conspicuousness to pollinators. The flowers are visited by various insects, specifically "Musca" flies. The flowers themselves come in a range of colors from a deep rust-orange to a pure yellow and often show striking gradients of color.

The plant propagates through its wind-dispersed seeds, and also vegetatively by stolons and shallow rhizomes.

Uses

"P. aurantiaca" is widely grown as an ornamental plant in gardens for its very decorative flowers. It has been introduced into Australasia and North America and escaped from gardens and is considered an invasive species in some areas. It is found across Canada and the north of the U.S., reaching more in the south on the coasts. The plant is easily removed by ploughing or salting, and it cannot be controlled by mowing because it regularly reproduces vegetatively. It is on the noxious weeds and/or quarantine lists of Colorado, Idaho, Montana, Oregon, Washington, and regions of British Columbia, with cultivation usually prohibited. In Alberta, it is not considered a noxious weed except locally. In Australia, the plant is considered a noxious weed in Tasmania and it is quarantined from the country. It has been recorded at Kosciuszko National Park in New South Wales, Falls Creek and Mount Buller in Victoria and Fern Tree and Snug in Tasmania. In New Zealand, the plant is closely watched and attempts at control are made.