Koenigia

Species of Koenigia are annual or perennial herbaceous plants, growing from taproots. The flowers are arranged in terminal or axillary inflorescences. The flowers have pale tepals: white, greenish to yellowish white or pink. The seeds are borne in achenes that are usually brown or black in colour and not winged.[2]

The genus Koenigia was erected by Carl Linnaeus in 1767, initially for the type species Koenigia islandica.[2] The boundaries between genera in the family Polygonaceae, and the relationships among them, have long been a problem. At one time, many species were placed in the genus Polygonum. Koenigia is placed in the subfamily Polygonoideae, tribe Persicarieae, whose taxonomic history has been described as "exceptionally convoluted, even by Polygonaceae standards".[2]

A molecular phylogenetic study of the subfamily Polygonoideae in 2015 showed that the genus Koenigia was polyphyletic with respect to the genus Aconogonon. An earlier study had reached a similar conclusion, and had suggested that extra genera be created to maintain monophyletic taxa.[3] The authors of the 2015 study preferred the alternative of merging the two genera,[2] a proposal accepted by other sources.[1] Using broad circumscriptions of the genera, the 2015 study suggested that relationships within the tribe Persicarieae were:[2]

Koenigia species are found in meadows, along stream banks, or on rocky slopes in arctic, temperate and alpine regions of the Northern Hemisphere.[3]