| | 1. Perianth red-violet; perennial herb; fruit hairy |
| B. coccinea |
| | 1' Perianth pale pink or white; annual; fruit glabrous |
| |
| | 2. Peduncle long, inflorescence umbel-like or flower 1 |
| |
| | 3. Ultimate 2 cm of branches with 0–1 branches, ending in umbel-like inflorescence; fruit length 3 × width |
| B. intermedia |
| | 3' Ultimate 2 cm of branches with 2–4 appressed side branches, each with 1–2 fruits; fruit length 2 × width |
| B. triquetra |
| | 2' Peduncle short, inflorescence a raceme-like spike |
| |
| | 4. Bracts deciduous, << fruit; fruit ridges generally 5; stem puberulent |
| B. coulteri |
| | 4' Bracts ± persistent, ± = fruit; fruit ridges generally 4; stem glandular-hairy |
| B. wrightii
|