Bistorta is an old genus name, now back in use. Around 46 species spread across much of the Northern hemisphere. All the plants were previously known as Persicaria and may still be sold under that name now.
One of the most important genera to have in a wildlife garden (indeed, any garden), bistortas produce nectar and pollen throughout their long flowering season, attracting honeybees, social wasps, butterflies and a host of other insects especially in the summer and early autumn. The leaves are relatively palatable also, and may be eaten by the caterpillars of a number of generalist moths. B. amplexicaulis is increasingly found away from gardens where it can persist, so care should be taken to avoid its spread away from cultivation.