Cyperaceae, the Sedge Family
Grass-like or rush-like plants, with linear leaves or leafless, and inconspicuous flowers in small chaffy spikes.
Over 200 species occur in Michigan, of which only the commonest are included here. For the remaining species the Manuals should be consulted.
| 1a. Spikes all alike — 2. | |
| 1b. The uppermost spike or spikes wholly staminate, the lower one or more pistillate; ovary and achene surrounded by a sac, the perigynium. Mature fruit is necessary for satisfactory identification (Sedge) — 12. | |
| 2a. Stems leafless, bearing one or more spikes at or near the top — 3. | |
| 2b. Stems leafy — 6. | |
| 3a. Spike one, terminal and erect (Spike Rush) — 4. | |
| 3b. Spikes usually more than one, lateral and spreading — 5. | |
| 4a. Annual, with fibrous roots | Spike Rush, Eleocharis obtusa. |
| 4b. Perennial, with a running rootstock | Spike Rush, Eleocharis palustris. |
| 5a. Stem round | Bulrush, Scirpus validus. |
| 5b. Stem 3-cornered | Three-square, Scirpus americanus. |
| 6a. Spikes axillary along the side of the stem | Dulichium, Dulichium, arundinaceum. |
| 6b. Spikes terminal — 7. | |
| 7a. Spikes subtended by long conspicuous leaves which greatly exceed the flower clusters — 8. | |
| 7b. Spikes not conspicuously exceeded by the bract-like leaves — 10. | |
| 8a. Spikes in a dense head-like cluster, white-woolly at maturity | Cotton Grass, Eriophorum virginicum. |
| 8b. Spikes not in dense heads, nor white-woolly at maturity — 9. | |
| 9a. Perennial by a creeping rootstock | Nut Grass, Cyperus esculentus. |
| 9b. Perennial by hard basal corms | Cyperus, Cyperus strigosus. |
| 10a. Bracts of the spike chestnut-brown | Twig Rush, Cladium mariscoides. |
| 10b. Bracts of the spike green or straw-color (Sedge) — 11. | |
| 11a. Spikes 3-8, separate | Sedge, Carex straminea. |
| 11b. Spikes very numerous and densely crowded | Sedge, Carex vulpinoidea. |
| 12a. Achenes flattened | Sedge, Carex crinita. |
| 12b. Achenes 3-angled — 13. | |
| 13a. Perigynium tipped with a sharp straight 2-toothed beak — 14. | |
| 13b. Perigynium with a short soft beak — 17. | |
| 14a. Perigynium thin and papery, loosely enclosing the achene — 15. | |
| 14b. Perigynium firm, closely enclosing the achene — 16. | |
| 15a. Perigynium less than 1 cm. long | Sedge, Carex hystericina. |
| 15b. Perigynium more than 1 cm. long | Sedge, Carex lupulina. |
| 16a. Perigynium smooth | Sedge, Carex riparia. |
| 16b. Perigynium hairy | Sedge, Carex filiformis. |
| 17a. Beak of the perigynium bent abruptly to one side | Sedge, Carex laxiflora. |
| 17b. Beak of the perigynium straight | Sedge, Carex pennsylvanica. |