Gentianella amarella

Gentianella amarella, the autumn gentian, autumn dwarf gentian, or autumn felwort, is a species of flowering plant in the gentian family, Gentianaceae. It is found throughout Northern Europe, the western and northern United States, and Canada.
It is a short biennial plant with elliptical to lanceolate leaves. The flowers are purplish bells between 12 and 22 mm long. It flowers between July and September. Its habitat is in grass, often on lime-rich soil (in England typically on chalk).