Allionia, commonly known as windmills or trailing four o'clock, is a genus of two species widespread in the western hemisphere. They are unusual in their blooms, which actually consist of three separate flowers appearing to be a single flower. The plants are finely pubescent annuals or short-lived perennials, with trailing stems up to a metre in length, often threading through other vegetation. The leaves range from oval to oblong, under 4 cm long. The inflorescences are axillary, consisting of three red-purple flowers symmetrically arranged and superficially seeming to be a single flower 3-15 mm across. The individual flowers are bisexual, bilaterally symmetric, with a distinct oblique funnel. The 5-7 stamens may be somewhat exserted, along with the style. The fruits have five ribs.