originates in Europe and Asia, and has spread across most other parts of the world, including all contiguous US states except Wyoming and North Dakota. Plants are creepers, with distinctive, reddish, four-sided stems, smooth green leaves and small, five-petaled flowers. Petals are round in shape and mostly colored pinkish-orange, with a darker, red to purple patch at the base. Petal edges are finely irregular, or toothed. The green calyx is split into five thin, pointed lobes, joined right at the base. The flower center contains five yellow-tipped stamens and a pistil. Petals open fully, often bending slightly below the plane. Flowers bloom only on sunny days, closing by the evening.