Pentanema britannicum

British yellowhead, in the Asteraceae (daisy) family, is a very recent introduction to North America. A native of Europe, this creeping perennial weed has been introduced to several nurseries in contaminated hostas and daylilies from the Netherlands. Once introduced, the plant spreads aggressively by thick, fleshy roots that produce new shoots.

Plants form rosettes of long, thin leaves that resemble some asters or fleabanes. The leaves also resemble buckhorn plantain leaves except plantain leaves have five distinct parallel veins; Inula leaves have netted veins. Leaves are up to 2 inches inches long and about 1/2 to 1 inch wide. Leaves remain green through the winter. Plants require a chilling period to flower. In the spring plants spread rapidly, then in early to mid-summer flowering stems begin to elongate. Plants produce attractive, typical aster-like flowers, yellow to light orange in color. They are found growing along river and stream margins, marshes, ditches, and wet woods and grasslands. However, it is an adaptable plant to other areas.

It is unclear whether or not the species produces viable seeds in North America. Because the plant primarily reproduces vegetatively, preemergence herbicides commonly used are not effective. It is nearly impossible to remove all of the root pieces; consequently, if a container plant is infested with British yellowhead it should be destroyed before the weed can spread.

This species is on the USDA list of Noxious Weeds.