| | 1. Flower and fruit enveloped in ± closed bract (perigynium) |
| |
| | 2. Perigynium open only at tip |
| CAREX |
| | 2' Perigynium open along 1 side |
| KOBRESIA (no key) |
| | 1' Flower and fruit not enveloped in a perigynium |
| |
| | 3. Generally only uppermost flowers bisexual and fruiting (lower staminate) |
| |
| | 4. Style base much expanded, persistent as tubercle on fruit |
| RHYNCHOSPORA |
| | 4' Style base little expanded, if persistent on fruit, not tubercle-like |
| |
| | 5. Perianth bristles 0; fruit not whitish and bony |
| CLADIUM (no key) |
| | 5' Perianth bristles present; fruit ± white, bony |
| SCHOENUS (no key) |
| | 3' Flowers generally bisexual only, fruiting (except sometimes lowest 1–3) |
| |
| | 6. Flower bracts 2-ranked |
| |
| | 7. Perianth bristles 5–8; spikelet clusters axillary, emerging from sheaths of stem leaves; fruit beak long |
| DULICHIUM (no key) |
| | 7' Perianth bristles 0; spikelet clusters generally terminal, not emerging from sheaths of stem leaves; fruit beak 0 |
| |
| | 8. Spikelet 1–many-flowered, generally not shed as unit |
| CYPERUS |
| | 8' Spikelet 1–2-flowered, shed as unit |
| KYLLINGA (no key) |
| | 6' Flower bracts spiraled |
| |
| | 9. Perianth bristles generally present |
| |
| | 10. Perianth bristles conspicuous, >> flower bract |
| ERIOPHORUM |
| | 10' Perianth bristles inconspicuous, hidden by flower bract |
| |
| | 11. Fruit top with tubercle of different color and texture; stem leaves 0 |
| ELEOCHARIS |
| | 11' Fruit top generally beaked, tubercle 0; stem leaves generally 1–several |
| SCIRPUS |
| |
| | 12. Flower subtended by bractlets and flower bract |
| LIPOCARPHA |
| | 12' Flower subtended only by flower bract |
| |
| | 13. Style ± equally wide throughout |
| SCIRPUS |
| |
| | 14. Fruit 3-sided, cells vertically elongate, top tubercled; style 3-branched, not fringed |
| BULBOSTYLIS (no key) |
| | 14' Fruit 2–3-sided or round, cells ± square or horizontally elongate, tubercle 0; style 2–3-branched, generally fringed below branches |
| FIMBRISTYLIS
|