Also known as Asian knotweed,  fleeceflower, crimson beauty, and Mexican bamboo, this herbaceous perennial is a member of the buckwheat family, Polygonaceae, that also includes rhubarb and dock. Although it is native to East Asia it was introduced into North America as an ornamental prior to 1890 and was used also for erosion control. It grows quickly to form thickets and is is now considered invasive in some areas. Japanese knotweed tolerates a wide range of conditions from sun to full shade, drought to occasional flooding, high temperatures, and high salinity. The plants do particularly well near waterways but also thrive in roadsides and waste places. On the other hand, bee keepers appreciate the nectar of the flowers for honeybees, various parts of the plant are used in traditional Chinese and Japanese medicine, and the young stems are edible, although very sour. Photo Credit Wikipedia

Description: Japanese knotweed grows 3-10′ tall and has erect, reddish brown stems that are hollow and swollen at the joints. The alternate leaves are 2-6″ long and have a pointed tip and square base. Clusters of small greenish-white or creamy-white male and female flowers appear in late summer on different plants. Pollinated female flowers are followed by a tiny ,1-seeded, dark brown, triangular fruit with a three-winged calyx. The rhizomatous root system is extensive and may reach down for 10 feet. Small root fragments can sprout and produce new plants.

Control: Japanese knotweed is difficult to control and may takes several years and the use of various techniques. For small young populations growing with desirable plants, careful hand digging can be effective but labor intensive because the whole root system must be removed to avoid resprouting of root fragments. Cutting the plants to the ground for several years will weaken the plants and eventually reduce their numbers. A heavy landscape fabric can be used to further weaken plants that emerge. This method will take up to 5 years and needs constant monitoring to flatten the plants that emerge and prevent them from growing through the cloth.

Severe infestations may require the use of a foliar herbicide such as a 2% solution of glyphosate or 2% solution of triclopy applied to thoroughly wet the leaves but not enough to drip. This is best done in late fall to reduce injury to desirable plants growing nearby.

By Karen