| | 1. Heads generally 1(–3) per flower stem |
| |
| | 2. Stem 5–12 cm; leaves thick, green above, tips notched |
| A. suffrutescens |
| | 2' Stem < 4 cm; leaves thin, gray-tomentose above, tips acute |
| |
| A. dimorpha |
| | 3' Plant bearing long, slender, ± leafless stolons |
| A. flagellaris |
| | 1' Heads 3–many per flower stem |
| |
| | 4. Plant without stolons, not forming mats |
| |
| | 5. Leaves cauline, ± equal; lower involucre densely tomentose |
| A. geyeri |
| | 5' Leaves basal and cauline, reduced upward; involucre ± glabrous |
| |
| | 6. Lower leaves 7–20 mm wide; stems 18–40 cm; phyllaries white or cream-colored, unequal |
| A. argentea |
| | 6' Lower leaves 2–5 mm wide; stems 10–25 cm; phyllaries straw-colored or pale, ± equal |
| A. luzuloides |
| | 4' Plant with stolons, forming mats |
| |
| | 7. Rosette leaves elliptic, green above; inflorescence raceme- or panicle-like, main axis 3–11 cm; peduncles 10–30 mm; inflorescence finely glandular |
| A. racemosa |
| | 7' Rosette leaves oblanceolate to spoon-shaped; inflorescence cyme-like, main axis ± 0; peduncles < 5 mm; inflorescence glandular or not |
| |
| | 8. Rosette leaves green or very lightly tomentose above, 1–3-veined |
| |
| | 9. Rosette leaves > 6 mm wide, 1–3-veined; cauline leaves 20–40 mm; inflorescence not glandular; Northwestern California |
| A. howellii subsp. howellii |
| | 9' Rosette leaves < or = 6 mm wide, 1-veined; cauline leaves 7–16 mm; inflorescence generally glandular; San Bernardino Mountains |
| A. marginata |
| | 8' Rosette leaves gray-tomentose above, 1-veined |
| |
| | 10. Phyllaries dark brown to black; stems 3–13 cm |
| |
| | 11. Lowest cauline leaf > 11 mm; herbage generally not glandular; pistillate corolla > 3 mm in fruit; staminate corolla generally > 2.7 mm in flower |
| A. media |
| | 11' Lowest cauline leaf < or = 11 mm; herbage generally glandular; pistillate corolla < or = 3 mm in fruit; staminate corolla generally < or = 2.8 mm in flower |
| A. pulchella |
| | 10' Phyllaries white to rose or pale brown; stems 6–40 cm |
| |
| | 12. Phyllaries white-tipped with a prominent blackish brown spot near base of scarious part |
| A. corymbosa |
| | 12' Phyllaries white, rose, straw-colored or (paler) brown, not dark-spotted near base |
| |
| | 13. Stolons slightly woody, ascending; phyllaries pale yellow to pale brown, tips blunt; staminate plants present — n High Sierra Nevada |
| A. umbrinella |
| | 13' Stolons not woody, horizontal or ascending; phyllaries various colors, tips acute; staminate plants ± 0 |
| A. rosea |
| | 14. Longest leaf of flower rosettes < 20 mm; phyllaries sometimes brown |
| subsp. confinis |
| | 14' Longest leaf of flower rosettes > 20 mm; phyllaries generally not brown |
| subsp. rosea
|