Flowers of the polygonaceae (buckwheat) family are generally very small, but produced in large clusters, which may be spherical, elongated or many-branched. Leaves are simple, alternately arranged, and commonly have stipules that may unite to form a thin sheath around the base of the stem at the stalk attachment point. Stems are often somewhat enlarged around the leaf nodes. Flowers have no petals, but instead are formed of petal-like sepals, usually colored. Most species have six sepals, often arranged in two rows of three; other species have three or four. Stamens number between three and nine. The US has 37 polygonaceae genera and 480 species.