| Family | Scientific Name | Common Name | Habitat | Distribution | Image |
|---|---|---|---|---|---|
| Rubiaceae | Cephalanthus occidentalis | Buttonbush, Honeyballs, Globe-flowers | Streambanks, riverbanks, depressional wetlands, lakes, marshes, often in standing water. | NL, ME, ON, MI, WI, MN, NE, NM, AZ, and CA south through Mexico to Guatemala and Honduras; Cuba (where uncertainly native). |  (c) Keim, Mary - CC-BY-NC-SA, permission granted to NCBG |
| Rubiaceae | Cephalanthus salicifolius | Mexican Buttonbush | Wet areas. | S. TX south to sc. Mexico. |