Verbenaceae, the Verbena Family
Herbs, with simple opposite leaves and slightly irregular flowers in spikes or heads; petals 5, united and bearing the 4 stamens in the corolla-tube; ovary 1, 2-celled or 4-celled, with 1 style.
| 1a. Plants prostrate or spreading — 2. | |
| 1b. Plants erect (flowers in summer) (Vervain) — 3. | |
| 2a. Leaves serrate; flowers in short dense spikes (flowers pale-blue, summer) | Fog Fruit, Lippia lanceolata. |
| 2b. Leaves pinnatifid; flowers in loose bracted spikes (flowers light-purple, summer) | Vervain, Verbena bracteosa. |
| 3a. Spikes dense, continuous (flowers purple or blue, varying to white) — 4. | |
| 3b. Spikes slender, interrupted, the flowers scattered (corolla white or pale-blue) — 6. | |
| 4a. Leaves lanceolate, manifestly petioled (1-2 m. high) | Vervain, Verbena hastata. |
| 4b. Leaves sessile, not lanceolate (5-8 dm. high) — 5. | |
| 5a. Leaves narrowly oblanceolate, tapering at the entire base | Vervain, Verbena angustifolia. |
| 5b. Leaves oblong to obovate, not tapering at the base | Vervain, Verbena stricta. |
| 6a. Leaves incised, tapering to a sessile base (5-10 dm. high) | Vervain, Verbena, officinalis. |
| 6b. Leaves serrate, petioled (1-2 m. high) | Vervain, Verbena urticaefolia. |