| silphium perfoliatum var. connatum | | USA: District of Columbia; US Botanic Garden National Garden. West of Conservatory | | 1243025627 |
| silphium perfoliatum var. connatum | | USA: District of Columbia; US Botanic Garden National Garden. West of Conservatory | | 1243024547 |
| silphium perfoliatum var. connatum | | USA: District of Columbia; US Botanic Garden National Garden. West of Conservatory | | 1243024270 |
| silphium perfoliatum var. connatum | | USA: District of Columbia; US Botanic Garden National Garden. West of Conservatory | | 1243023873 |