Knotweed is a tufted ground cover plant with dark green, tapered leaves on creeping stems. Tiny, bright rose flowers bloom in dense spikes about 8 inches high from late summer into fall. Easy to grow. This plant requires good soil, preferably slightly moist, in full sun. The plant is good as a ground cover or as an edging plant for the bed or border. It is especially valuable because the plant sends up new flowers over a long period.