What is Japanese Knotweed
The stems grow vigorously from mid to late May dominating areas and creating stands where it is the only species present. The dried stems from previous years are generally present. Fresh stems are green and red with a similar appearance to rhubarb and can grow in excess of two metres in height. The leaves have a stem, are oppositely arranged on the stem. Stems are hollow. Later in the season small creamy white flowers appear in the leaf axils.
Method of Spread
Rhizomes (underground stems that are capable of producing the stems and roots of another plant) grow rapidly underground producing long white shoots at the tips which send up shoots to the surface. Disturbance increases the stem density and if the tops are cut it is important to dispose of them properly.
All Japanese Knotweed plants within the UK are female and all male plants are shown to be infertile hybrids. Japanese Knotweed has an incredible capacity to spread: as little as a 10mm2, 0.7 gm section of rhizome has the capacity to produce a whole new plant. The plant spreads vegetatively from stems, crown and rhizomes and has spread throughout the entire UK since its arrival here in 1854.