German knotweed (annual knawel)

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.