| Rubiaceae |
|
Houstonia purpurea
| L. | Sp. Pl. 1: 105 | 1753 |
| Rubiaceae |
|
Houstonia purpurea var. calycosa
| A. Gray | Syn. Fl. N. Amer. 1(2): 26 | 1884 |
| Rubiaceae |
|
Houstonia purpurea var. ciliolata
| (Torr.) A. Gray | Manual ed. 5: 212 | 1867 |
| Rubiaceae |
|
Houstonia purpurea var. longifolia
| (Gaertn.) A. Gray | Manual ed. 5: 212 | 1867 |
| Rubiaceae |
|
Houstonia purpurea var. montana
| (Small) Terrell | Rhodora 61: 169 | 1959 |
| Rubiaceae |
|
Houstonia purpurea fo. pubescens
| (Britton) Fernald | Rhodora 38(456): 444 | 1936 |
| Rubiaceae |
|
Houstonia purpurea var. pubescens
| Britton | Mem. Torrey Bot. Club 4: 125 | 1894 |
| Rubiaceae |
|
Houstonia purpurea fo. purpurea
| | | |
| Rubiaceae |
|
Houstonia purpurea var. purpurea
| | | |
| Rubiaceae |
|
Houstonia purpurea var. tenuifolia
| (Nutt.) A. Gray | Syn. Fl. N. Amer. 1(2): 26 | 1884 |