Iridaceae, the Iris Family
Herbs, with 6-parted perianth, inferior ovary, and 3 stamens.
| 1a. Flowers blue, 5 cm. wide or larger — 2. | |
| 1b. Flowers about 1 cm. wide (blue or white, from a spathe terminating a 2-edged stem 2-5 dm. high, spring and early summer) (Blue-eyed Grass) — 3. | |
| 2a. Flowering stems 4-8 dm. high (early summer) | Blue Flag, Iris versicolor. |
| 2b. Flowering stems 2 dm. or less high (spring) | Dwarf Iris, Iris lacustris. |
| 3a. Spathes terminal, sessile — 4. | |
| 3b. Spathes long-peduncled, axillary — 8. | |
| 4a. Spathe single — 5. | |
| 4b. Spathes 2 on each flowering stem — 7. | |
| 5a. Pedicels much longer than the inner (shorter) bract | Blue-eyed Grass, Sisyrinchium mucronatum. |
| 5b. Pedicels equaling or barely exceeding the inner bract — 6. | |
| 6a. Capsule brown; common species | Blue-eyed Grass, Sisyrinchium angustifolium. |
| 6b. Capsule green or yellowish; rare species | Blue-eyed Grass, Sisyrinchium montanum. |
| 7a. Leaves folded lengthwise; stems narrowly winged | Blue-eyed Grass, Sisyrinchium hastile. |
| 7b. Leaves flat; stem broadly winged, 2-3 mm. wide | Blue-eyed Grass, Sisyrinchium albidum. |
| 8a. Capsules pale straw-color or whitish — 9. | |
| 8b. Capsules brown, or tinged with purple — 10. | |
| 9a. Plant with straight fibrous bristles at base; pedicels long-exserted | Blue-eyed Grass, Sisyrinchium farwellii. |
| 9b. Plants not bristly at base; pedicels barely exserted | Blue-eyed Grass, Sisyrinchium strictum. |
| 10a. Pedicels scarcely exceeding the inner bract — 6a. | |
| 10b. Pedicels much exceeding the inner bract — 11. | |
| 11a. Stem 2-6 mm. wide; bracts 1.5-2 cm. long | Blue-eyed Grass, Sisyrinchium gramineum. |
| 11b. Stem 1-2 mm. wide; bracts 1-1.5 cm. long | Blue-eyed Grass, Sisyrinchium apiculatum. |