| 1. Herbs, base sometimes woody; axillary leaf clusters generally 0 |
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| 2. Leaves generally entire, < 5 mm wide, anise- or tarragon-scented |
| A. dracunculus |
| 2' Some leaves lobed, generally > 5 mm wide; odor, if any, not anise- or tarragon-scented |
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| 4' Leaves generally 18 cm wide, ± glabrous above, glabrous or hairy below; stems 325 dm |
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| 5. Lowest leaves 2-pinnately divided, lateral lobes acute; leaves generally glabrous above, tomentose (or becoming glabrous) below; strongly lemon-scented; subalpine to alpine |
| A. michauxiana |
| 5' Leaves entire to pinnately lobed, lateral lobes obtuse to acute, green and glabrous above, densely tomentose below; ± scented (not lemony); coastal and inland valleys |
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| 6. Involucre bell-shaped, 24 mm diam; phyllaries gray-hairy, ovate; flowers > 15; leaves green to gray-green above |
| A. douglasiana |
| 6' Involucre narrow, < 2 mm diam; phyllaries yellowish, glabrous to sparsely hairy, oblong to ± ovate; flowers < 15; leaves dark green above |
| A. suksdorfii |
| 4. Leaves generally < 1 cm wide, densely gray-hairy (or becoming ± glabrous above); stems generally < 8 dm |
| A. ludoviciana |
| 7. Inflorescence open; leaves generally 12 cm |
| subsp. albula |
| 7' Inflorescence narrow; leaves generally 211 cm |
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| 8. Leaves entire to toothed or shallowly lobed |
| subsp. ludoviciana |
| 8' Leaves deeply 12-divided into narrow lobes |
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| 9. Involucre 45 mm, 47 mm diam; leaves white-tomentose |
| subsp. candicans |
| 9' Involucre 2.53.5 mm, 23.5 mm diam; leaves upper surface often green |
| subsp. incompta |
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| 10. Stem glabrous, simple, basal leaves 0 |
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| 11. Perennial; stem wand-like, > 8 dm; leaves coarsely lobed; receptacle chaffy s South Coast, Peninsular Ranges |
| A. palmeri |
| 11' Annual or biennial; stem erect, < 8 dm; leaves finely divided; receptacle naked |
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| 12. Heads nodding; annual, aromatic; leaves 23-pinnately divided |
| A. annua |
| 12' Heads erect; biennial, unscented; leaves 2-pinnately divided |
| A. biennis |
| 10' Stem hairy, branched from base, from basal leaf cluster |
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| 13. Leaves densely hairy; phyllaries densely gray-hairy, margins widely scarious; coastal |
| A. pycnocephala |
| 13' Leaves glabrous or ± hairy; phyllaries sparsely hairy, margins dark or scarious; montane |
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| 14. Biennial or perennial herb from taproot; inflorescence narrow, spike-like, phyllary margins scarious |
| A. campestris subsp. borealis |
| 14' Perennial from branched caudex; inflorescence open, phyllary margins black |
| A. norvegica subsp. saxatilis |
| 1' Subshrubs or shrubs; axillary leaf clusters present |
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| 15. Plant spiny, compact (hairy); inflorescence short, heads ± hidden by leaves; leaves palmately 35-divided; flower spring/early summer |
| A. spinescens |
| 15' Plant unarmed, compact to tall; inflorescence long, stalked, generally ± exceeding leaves, heads not hidden; leaf lobes 05; flowering late summer/autumn |
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| 16. Leaves generally > 2 cm, linear, often ± thread-like or lobes < 3 mm wide, generally > 1 cm |
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| 17. Plant 618 dm; leaf segments generally < 1 mm wide, margins curled under; mainland, some Channel Islands |
| A. californica |
| 17' Plant generally < 6 dm; leaf segments 13 mm wide, flat; s Channel Islands |
| A. nesiotica |
| 16' Leaves generally < 2 cm, oblong or wedge-shaped, generally > 3 mm wide, entire to shallowly 3-lobed at tip, lobes < 1 cm |
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| 18. Heads nodding; leaves not clustered, entire or teeth 3, sharply pointed White and Inyo Mountains, Mojave Desert |
| A. bigelovii |
| 18' Heads erect; leaves often in axillary clusters, entire or teeth 3, rounded to acute |
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| 19. Leaves generally linear, entire, winter-deciduous; heads generally > 5 mm wide |
| A. cana subsp. bolanderi |
| 19' Leaves generally wedge-shaped, 3-toothed, persistent in winter; heads generally < 5 mm wide |
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| 20. Plant generally < 4 dm; inflorescence narrow, generally < 3 cm wide |
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| 21. Shrub with evident trunk at base |
| A. tridentata subsp. wyomingensis |
| 21' Shrub branched at base, trunk not evident |
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| 22. Leaves of flower-stems entire; heads < 3 mm diam, solitary on slender peduncle; phyllaries shiny-resinous, straw-colored |
| A. nova |
| 22' Leaves of flower-stems lobed; heads generally > 3 mm diam, sessile, 24 per cluster; phyllaries gray-hairy |
| A. arbuscula |
| 23. Leaves of flower-stem shallowly lobed; heads 34 mm diam |
| subsp. arbuscula |
| 23' Leaves of flower-stem deeply lobed; heads 23 mm diam |
| subsp. thermopola |
| 20' Plant generally > 4 dm; inflorescence > 3 cm wide |
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| 24. Plant sticky-resinous; heads > 3 mm diam; meadows, c&s High Sierra Nevada, San Gabriel Mountains, San Bernardino Mountains |
| A. rothrockii |
| 24' Plant not sticky; heads generally < 3 mm diam (4.56 mm in A. spiciformis); widespread in mtns, dry valleys |
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| 25. Leaves entire to irregularly 36-lobed, partly deciduous; plant sprouting from roots; high mtn meadows |
| A. spiciformis |
| 25' Leaves generally regularly 3-lobed, wedge-shaped, evergreen; plant not root-sprouting; widespread |
| A. tridentata |
| 26. Inflorescence narrow, branches generally erect |
| subsp. vaseyana |
| 26' Inflorescence wide, branches erect to spreading or drooping |
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| 27. Inflorescence branches drooping; fruit hairy |
| subsp. parishii |
| 27' Inflorescence branches erect to spreading; fruit glandular |
| subsp. tridentata
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