| | 1. Cauline leaves petioled, lower and middle pinnately lobed, rarely just dentate; fruit ± flat parallel to septum to cylindric, rarely ± 4-sided; style ± club-shaped or obconic |
| |
| | 2. Fruit pedicel ± straight, spreading, rarely ascending; stem solid, not inflated; fruit spreading; petal blades linear |
| T. laciniatum |
| | 2' Fruit pedicel upcurved, generally erect at tip; stem generally ± hollow to inflorescence, inflated or not; fruit ± erect, often appressed; petal blades oblanceolate to spoon-shaped |
| T. milleflorum |
| | 1' Cauline leaves sessile, lower and middle generally entire, rarely dentate; fruit cylindric; style cylindric or tapered to tip |
| |
| | 3. Perennial, caudex thick, covered with many old petiole bases; stem subdecumbent to erect, generally wavy; basal leaves persistent; petioles glabrous |
| T. flexuosum |
| | 3' Winter annual, biennial, with few old petiole bases at base or not, if perennial herb then rhizome slender, without old petiole bases; stem generally erect, straight; basal leaves withering early; petioles often hairy |
| |
| | 4. Cauline leaves narrowed to base, ± without basal lobes, ascending |
| T. integrifolium |
| | 5. Petals white; fruit pedicel whitish, 6–13 mm, stalk above receptacle 1–3 mm |
| subsp. affine |
| | 5' Petals lavender to purple, rarely whitish; fruit pedicel not whitish, 2–5(6) mm, stalk above receptacle 0.5–1 mm |
| subsp. complanatum |
| | 4' Cauline leaves expanded to base, with basal lobes, erect-appressed to ascending |
| |
| | 6. Inflorescence dense, spike-like; petals generally white, rarely light lavender, blades often crinkled; fruit pedicel erect, if ± ascending to spreading then < 2.5 mm |
| |
| | 7. Fruit pedicel 1–2 mm, spreading, rarely ± ascending, stout, base flat; seed plump |
| T. brachycarpum |
| | 7' Fruit pedicel 2–6 mm, erect to erect-ascending, partly or fully appressed, slender, base not flat; seed ± flat |
| T. crispum |
| | 6' Inflorescence open, not spike-like; petals lavender or purple, rarely white, blades not crinkled or only so at base; fruit pedicel ascending, rarely ± spreading, 3–8 mm |
| |
| | 8. Paired filaments partly to completely fused; petals spoon-shaped |
| T. howellii subsp. howellii |
| | 8' Paired filaments free; petals linear |
| T. stenopetalum
|