About Polygonum douglasii Greene
Polygonum douglasii Greene is a species of flowering plant in the knotweed family, commonly called Douglas's knotweed. It is native to most of northern and western North America, where it grows in many types of habitat, including disturbed areas. In Canada, it has been recorded from British Columbia north to Yukon, and east as far as Québec; in the United States, it occurs as far south as California, New Mexico, Iowa, and New York. P. douglasii is recognized as a species complex, as its many subspecies may actually be better classified as separate distinct species. The species is morphologically variable, and its subspecies are often hard to tell apart. In general, plants in this complex are annual herbs that grow erect, reaching a maximum height between 3 and 80 centimeters (1.2–32 inches), with thin, angular stems. Plants growing at high elevation are smaller, and sometimes trail along the ground surface. Its leaves are linear or broadly lance-shaped; they sometimes drop off to leave the plant mostly bare during flowering, or are reduced to tiny scales at stem tips. Its flowers are a few millimeters long, ranging in color from pink to white, and may stay closed or open all together in a cluster.
