Crimson Knotweed is plant characterized by crimson broad-cylindrical or rounded dense flower spikes, 1.5-4 cm long. Flowers are about 4 mm. Leaves are oblong-blunt, up to a foot long and 2-4 cm broad, with the base narrowing into a leaf-stalk which has narrow wings. Upper leaves are stem clasping. The plant is 20-50 cm tall, with a stout root-stock. The stem is often covered with bases of old leaves. Crimson Knotweed is found in the Himalayas, from West Nepal to SW China, at altitudes of 3000-4000 m. Flowering: June-September.