Scleranthus annuus is a species of flowering plant in the pink family known by the common names German knotweed and annual knawel. It is native to Europe, Asia, and North Africa, and it is known throughout the rest of the temperate world as an introduced species and a common weed. It grows in many types of habitat, often in disturbed areas. It is an annual herb with low, spreading stems up to 15 centimeters long growing from a taproot. The leaves are needle-like or linear in shape with sharp, stiff points. They are oppositely arranged in pairs about the stem and are fused together at the bases. Flowers occur in pairs or small clusters of up to five. The flowers lack petals but have bell-shaped calyces of green petal-shaped sepals.