The photo at right shows a flower head of hairy arnica (Arnica mollis).

1. Meadow Arnica: Arnica chamissonis - 5-12 pairs of stem leaves. Tips of involucral bracts blunt to slightly acute, bearing a tuft of whitish hairs. Flower heads with 8-15 rays measuring 1-2 cm long.

2. Heartleaf Arnica: Arnica cordifolia - 2-4 pairs of stem leaves. Flower heads of ray flowers surrounding a central disk. Blades of basal and stem leaves heart-shaped. Involucre with many whitish hairs.

3. Rayless Arnica: Arnica discoidea - Heads completely discoid. No ray flowers present. 2-4 pairs of stem leaves. Flower heads not nodding prior to bloom.

4. Slender Arnica: Arnica gracilis (A. latifolia var. gracilis) - 2-4 pairs of stem leaves. Flower heads of ray flowers surrounding a central disk.Flower heads of ray flowers surrounding a central disk. Basal leaves present, usually not with heart-shaped blades. Stem leaves not heart-shaped. Involucres glabrous or with few whitish hairs. (Similar to mt. arnica.)

5. Mountain Arnica, Broadleaf Arnica: Arnica latifolia - 2-4 pairs of stem leaves. Flower heads of ray flowers surrounding a central disk. Basal leaves present, usually not with heart-shaped blades. Stem leaves not heart-shaped. Involucre glabrous or with few whitish hairs. (Similar to slender arnica.)

6. Spearleaf Arnica: Arnica longifolia - 5-12 pairs of stem leaves. Tips of involucral bracts acute, lacking a tuft of whitish hairs at the tip.

7. Hairy Arnica: Arnica mollis - 2-4 pairs of stem leaves. Flower heads of ray flowers surrounding a central disk. Basal leaves lacking, the lowest stem leaves usually the largest.. Flower heads broad. Pappus of featherlike, light brown bristles.

8. Nodding Arnica: Arnica parryi ssp. parryi - 2-4 pairs of stem leaves. Flower heads discoid, generally lacking ray flowers. Flower heads nodding prior to bloom.

9. Rydberg's Arnica: Arnica rydbergii - 2-4 pairs of stem leaves. Flower heads of ray flowers surrounding a central disk.