| | 1. Leaf pinnately compound, leaflets 3–5; petals 0 |
| A. negundo var. californicum |
| | 1' Leaf simple, palmately lobed; petals present |
| |
| | 2. Leaf 10–25 cm wide; inflorescence long, pendent, flowers > 30; fruit body brownish hairy |
| A. macrophyllum |
| | 2' Leaf 2–12 cm wide; inflorescence a dense raceme, flowers generally < 10; fruit body glabrous |
| |
| | 3. Leaf 5–12 cm wide; fruit wings widely spreading (nearly 180°) |
| A. circinatum |
| | 3' Leaf 2–5 cm wide, fruit wings overlapping or spreading < 45° |
| A. glabrum |
| | 4. Twigs generally whitish; leaf generally 1.2–2.8 cm wide |
| var. diffusum |
| | 4' Twigs generally reddish; leaf generally 3–5 cm wide |
| |
| | 5. Fruit wings overlapping |
| var. greenei |
| | 5' Fruit wings spreading ± 45° |
| var. torreyi
|