There are many species of plants that contain Indican (precursor of indigo/indigotin), and they are cultivated worldwide to extract the blue colors.
From Left, Indigofera Tinctoria (image from wikipedia), Isatis Tinctoria (image from wikipedia), Persicaria Tinctoria (image from mika)
Indigofera Tinctoria (true indigo) is a species of plant from the bean family. It is cultivated in India and southeast Asia to extract Indigo. The native range of this species is tropical West Africa,South Africa and the Indian subcontinent to Mainland Southeast Asia and it requires a tropical climate. It contains the most indigo among all the indigo containing plants.
Indigofera suffruticosa (Guatemalan indigo, anil) is a flowering plant in the pea family, Fabaceae. Anil is native to the subtropical and tropical Americas. It is an erect branching shrub growing to 1m tall with pinnate leaves, and is commonly found growing in dry, highly disturbed areas such as roadsides and fallow fields.
Strobilanthes Cusia is a perennial flowering plant of the family Acanthaceae. Native to South Asia, China, and Indochina, it was historically cultivated on a large scale in India and China as a source of indigo dye. It requires a tropical moist climate.
Isatis Tinctoria (woad, färberweid, pastel) is a flowering Biennial plant in the family Brassicaceae, native to South-Eastern and Central Europe and it has been cultivated widely for the use as a blue dye source. However the concentration of indigo in the plant is significantly lower than the other species.
Persicaria Tinctoria ( Chinese indigo, Japanese Indigo, Tade Ai, dyer’s knotweed, Färber Knöterich) is a species of flowering plant in the buckwheat family. Annual plant. It is native to Eastern Europe and Asia. Colour is extracted through water extraction or by composting leaves called “Sukumo”. It does not contain indigo as much as Indigofera, but it contains more than Isatis. Suitable for a temperate climate.
Circular Blue project plans to grow both the Persicaria Tinctoria and Isatis Tinctoria at the Elisabeet. Both of the plants suits well with the Berlin temperate climate region.