Araceae, the Arum Family
Individual flowers small, but crowded on a fleshy spadix to form a conspicuous spike, usually surrounded by a green or colored spathe.
| 1a. Leaves compound — 2. | |
| 1b. Leaves simple — 3. | |
| 2a. Leaflets 3, spathe pale green or purple (3-6 dm. high; spring) | Indian Turnip, Arisaema triphyllum. |
| 2b. Leaflets 7-11; spathe green; spadix long and slender (3-8 dm. high; late spring) | Dragon Root, Arisaema dracontium. |
| 3a. Leaves linear, sword-shape; spathe none (5-15 dm. high; early summer) | Sweet Flag, Acorus calamus. |
| 3b. Leaves broader than linear; spathe present — 4. | |
| 4a. Flower clusters partly underground, appearing in earliest spring | Skunk Cabbage, Symplocarpus foetidus. |
| 4b. Flower clusters peduncled, in early summer — 5. | |
| 5a. Leaves broadly ovate-cordate; spathe white | Water Arum, Calla palustris. |
| 5b. Leaves more or less sagittate; spathe green | Arrow Arum, Peltandra virginica. |