Physostegia is a genus of flowering plants in the family Lamiaceae (the mint family), belonging to the order Lamiales. Commonly known as lionshearts or false dragonheads — the latter name referring to their resemblance to the related genus Dracocephalum — the genus comprises around a dozen species of erect, rhizomatous herbaceous perennials native entirely to North America, ranging from the United States and Canada south into northern Mexico.
Plants typically grow up to 2 metres (7 ft) tall, forming clumps via spreading rhizomes. The flowers are tubular, two-lipped, and borne in upright terminal racemes, typically in shades of purple or pink, appearing in summer. The genus inhabits damp, sunny habitats such as streambanks, wet meadows, and floodplain margins.
The best-known member of the genus is Physostegia virginiana, the obedient plant, widely cultivated in temperate gardens. Its common name derives from the quirk that individual flowers can be repositioned on the stem and will remain where placed, due to the structure of the short pedicel. GBIF records 14 descendant taxa in the genus.
Etymology
The genus name Physostegia derives from two Greek words: physa (bladder) and stege (covering or roof), together describing the calyx, which inflates and encloses the fruit when seeds mature.
Distribution
All species are native to North America. The genus ranges across much of the eastern and central United States and Canada, with some species extending west to British Columbia and south into northern Mexico. Individual species tend to have more restricted ranges — for example, P. ledinghamii is confined to the Prairie provinces and adjacent northern US states, while P. purpurea and P. digitalis are restricted to the southeastern US.
Ecology
Physostegia species inhabit damp, sunny environments including streambanks, wet prairies, and floodplain margins across North America. They are rhizomatous perennials that can spread vegetatively in suitable moist soils.
Cultivation
Physostegia virginiana is the species most widely grown in gardens and is valued for its upright habit, late-summer bloom, and tolerance of moist soils. Its common name "obedient plant" reflects the flower's notable characteristic: individual blooms on the raceme can be repositioned and will stay in place due to the flexible pedicel joint.
