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| 1 Perennial, from a stout rhizome; [subgenus Geranium]. |
| ..2 Cymules 1-flowered (rarely a few cymules 2-flowered); pedicels with eglandular hairs only. |
| ....3 Petals 15-22 mm long; fruit 28-42 mm long |
| ....3 Petals 4-6 mm long; fruit 14-20 mm long |
| ..2 Cymules 2-flowered; pedicels with a mixture of glandular and eglandular hairs (except with eglandular hairs only in G. maculatum). |
......4 Pedicels with eglandular hairs only; petals 11-16 mm long; [native, common in much of our area (and also sometimes cultivated)] |
| ......4 Pedicels with a mixture of glandular and eglandular hairs; petals either 6-9 or 12-29 mm long; [alien, rare and in disturbed situations]. |
| ........5 Fruit 30-37 mm long; petals 12-24 mm long |
| ........5 Fruit 14-27 mm long; petals either 6-9 mm long or 15-29 mm long. |
| ..........6 Petals 15-29 mm long; mericarp callus absent; fruits 15-27 mm long |
| ..........6 Petals 6-9 mm long; mericarp callus present; fruits 14-20 mm long |
| 1 Annual, from a taproot. |
| ............ 7 Leaves compound, at least the terminal segment (and often also the two lateral segments) petiolulate, not connected to the lateral segments by leaf tissue; petals 9-14 mm long; [rare in our area, mainly northward]; [subgenus Robertium, section Ruberta] |
| ............ 7 Leaves dissected, but not compound, all segments interconnected by leaf tissue; petals 2-10 mm long; [collectively common and widespread in our area]. |
| ............ ..8 Sepals blunt or acute, or terminating in a minute callus tip (mucro) < 0.3 mm long; [subgenus Robertium, section Batrachioidea]. |
| ............ ....9 Mericarps appressed pubescent across the surface, not ridged; stem pubescence of short (< 0.3 mm long), gland-tipped and eglandular hairs; stamens partly sterile (the inner 5 fertile, the outer 5 lacking anthers) |
| ............ ....9 Mericarps glabrous across the surface (slightly to densely ciliate at the base), either reticulately ridged or not; stem pubescence an admixture of long eglandular hairs (1.0-1.7 mm long) and short (< 0.5 mm long) gland-tipped and eglandular hairs; stamens (all 10) fertile (note that anthers may fall readily). |
| ............ ......10 Mericarps not reticulately ridged |
| ............ ......10 Mericarps reticulately ridged |
| ............ ..8 Sepals awned or subulate, the subulate awn 0.7-3 mm long. |
| ............ ........11 Mature pedicels < 1.5× as long as the calyx. |
| ............ ..........12 Mericarps with spreading hairs about 0.5 mm long, these often gland-tipped; [subgenus Geranium, section Dissecta] |
| ............ ..........12 Mericarps with long appressed hairs about 1 mm long, these not gland-tipped; [subgenus Geranium, section Geranium] |
| ............ ........11 Mature pedicels > 2× as long as the calyx; [subgenus Geranium, section Geranium]. |
| ............ ............ 13 Pedicels glandular-villous |
| ............ ............ 13 Pedicels retrorsely strigose |