This rare, bone-hardy, enigmatic, but vigorous plant forms a rosette of coarsely-toothed, kidney-shaped leaves, from which, in August, arise several stems bearing "night-sky" sprays of starry, dark purple-maroon flowers. It comes from partly shady wet spots, at the sides of streams and ravines on Japan's northern island, Hokkaido. Also on, Honshu, on the road from Takayama to Matsumoto!
Seeds can be sown at any time but are best sown in winter or early spring to benefit from a cold spell in the wet compost to break their dormancy. We advise covering seeds very thinly with sand or fine grit to about the depth of the seed size. If the seeds do not come up within 6 to 12 weeks the damp seed tray can be given cold treatment in a fridge for about four weeks. They may still take very many months to appear, so please never discard the pot or tray.