Corydalis /Fumewort (common name) – this lovely weed is springing up everywhere around us right now, flowering along with the somei yoshino sakura. Corydalis is a genus of about 300 species of annual and perennial herbaceous flowering plants in the family Fumariaceae, native to the temperate Northern Hemisphere and also southern Africa. Central Asia and Western China, along with some in South Africa, have the heaviest concentrations. These plants do well in shade and moist soil.
The plant contains many alkaloids. Native Americans placed the root on coals and inhaled the smoke to “clear the head…”and early American doctors may have used the bitter, astringent root to stop bleeding, for irregular menses, pain, diarrhea and dysentery. There may be some Chinese studies to suggest that Corydalis alkaloids may be muscle relaxants, analgesic and may slow the flow of gastric secretions.
Warning: Corydalis may be toxic even in low doses. Symptoms may include trembling and convulsions.
To see what species are available in Japan, see this link.