Persicaria tinctoria (also known as Dyer’s Knotweed or Japanese Indigo) is a flowering plant from the buckwheat family and native to Eastern Europe and Asia. There are different varieties of Persicaria tinctoria including Kojōko with white flowers and pointed leaves and Senbon with pink flowers and rounded leaves. The soft and dark green leaves of this annual plant have a high concentration of indigo.
Persicaria tinctoria is a plant with jointed stem nodes and will root from the nodes on the stem. Burying the nodes helps the plant to root better. And you can also increase the number of plants by bending branches and tucking them into the soil.
Persicaria tinctoria grows well in sunny spots with weekly watering in well-drained neutral soil. In the greenhouse, persicaria plants start flowering in late August, outdoors not until early October.