Lobeliaceae, the Lobelia Family
Herbs with alternate simple leaves and milky juice; flowers irregular; petals 5, united; corolla split down the upper side; stamens 5, united by their anthers into a ring or tube surrounding the style; ovary 2-celled, inferior. Flowers in summer and autumn.
| 1a. Leaves all basal, tubular; flowers on leafless stalks (aquatic, 1-4 dm. high; flowers blue) | Water Lobelia, Lobelia dortmanna. |
| 1b. Leaves normal, on the stem — 2. | |
| 2a. Flowers more than 2 cm. long (5-10 dm. high) — 3. | |
| 2b. Flowers about 1 cm. long, or shorter (flowers light blue) — 4. | |
| 3a. Flowers scarlet | Cardinal Flower, Lobelia cardinalis. |
| 3b. Flowers blue | Great Lobelia, Lobelia siphilitica. |
| 4a. Flowers in loose racemes, pedicelled — 5. | |
| 4b. Flowers in slender terminal spike-like racemes, nearly sessile (4-10 dm. high, usually unbranched) | Lobelia, Lobelia spicata. |
| 5a. Foliage pubescent (3-8 dm. high) | Indian Tobacco, Lobelia inflata. |
| 5b. Foliage glabrous (1-4 dm. high) | Lobelia, Lobelia kalmii. |