| | 1. Annual, sterile leaf-clusters 0, caudices 0; basal leaves 0 or few, shed before fruit complete; fruit 10–15 mm wide |
| T. arvense |
| | 1' Perennial, generally with sterile leaf-clusters from branched caudices; basal leaves generally many; fruit < 6 mm wide |
| |
| | 2. Fruit 2–3 × longer than wide, tip acute; pedicel ascending; basal leaves sparsely dentate |
| T. californicum |
| | 2' Fruit 1–2 × longer than wide, tip generally truncate or notched, rarely acute; pedicel spreading to ± ascending; basal leaves ± entire |
| T. montanum var. montanum
|