''Penthorum'' is a genus of plants in the order

Saxifragales Saxifragales is an order (biology), order of flowering plants in the Superrosids, superrosid clade of the eudicots. It contains 15 Families (biology), families and around 100 genera, with nearly 2,500 species. Well-known and economically import ...

. They are erect herbaceous perennials about half a meter tall. The genus consists of two species, one from east Asia and one from eastern North America. It is variously classified in the family

Saxifragaceae Saxifragaceae is a family of Herbaceous plant, herbaceous Perennial plant, perennial flowering plants, within the core eudicot Order (biology), order Saxifragales. The Taxonomy (biology), taxonomy of the family has been greatly revised and the ...

or its own family Penthoraceae. Its closest relatives may be in

Haloragaceae Haloragaceae (the watermilfoil family) is a eudicot flowering plant family in the order Saxifragales, based on the phylogenetic APG system. In the Cronquist system, it was included in the order Haloragales. Description The Haloragaceae ...

References

Saxifragales Saxifragales genera {{Saxifragales-stub