The birthwort is showing whorls of slender tubular flowers on the Systematic Beds.
The genus Aristolochia contains over 300 species of evergreen or deciduous climbers, shrubs and perennials from woodland in temperate and tropical regions. Many have very showy, petalless flowers, which can be coloured either white, yellow, purple, brown or maroon, or a combination of these, and they have a distinctly shaped flower which has earned them the common name of Dutchman’s pipes. A. clematitis has clusters of slender, tubular, yellow or brown hermaphrodite flowers, with pointed, curved upper lips. During the female stage the flowers attract flies, which are trapped by hairs in the throat of the flower. Whilst trapped the flies feed on nectar and deposit pollen on the stigmatic surfaces. When the flower develops into the male stage the flies are covered in pollen. The fly can emerge from the flower when the hairs shrivel, to repeat the process in another flower. Once pollinated, small, spherical, melon-like fruits are produced, as can be seen here amongst the twining stems.