Known variously as Japanese or Chinese Indigo, or Dyer's Knotweed,this is a tender annual used for centuries in the East to produce a blue dye with the same chemistry as that in the Indian Indigo plant (Indigofera tinctoria), but it is much easier to grow (in the UK - believe me, I have tried!) and to use. Seed is however difficult to come by and said to be not viable for very long.
I used to import fresh seed from the latest harvest in USA, but now has to include a phytosanitary inspection charge as well as import duty, so the supplier does not want to send anymore; you may find some small amount of seed on eBay. We have a few plants available in spring. (see our Natural Dye Plants section to buy plants, and Books section for books that describes its cultivation and dye use.)
It needs warm, humid conditions to germinate and to grow. Best sown in a heated propagator in Spring and only planted outside after the beginning of June in the UK.
It is NOT the same plant as the infamous "Japanese Knotweed", though it is in the same family! It cannot become invasive as it dies completely in winter. It has pretty spikes of pink flowers which are good in the border and attract insects.
