Aquatic and Wetland Vascular Plants of the Northern Great Plains
40. Verbenaceae, the Vervain Family
2. Verbena L. -- Vervain1. Verbena hastata L. -- Blue vervain
Stout, erect, perennial herb 4-12 dm tall from a thick rootstock; stem simple from the base, sometimes branched above, 4-angled, hispid to strigose. Leaves simple, opposite, short-petioled, the blades lanceolate to ovate-lanceolate or elliptic-lanceolate, 4-12 cm long, 1-5 cm wide, scabrous with stiff appressed hairs, acute to attenuate at the tip, coarsely serrate, occasionally lobed near the base, cuneate to rounded at the base and decurrent on the petiole. Inflorescence of (1) few to many, dense, bracteate spikes terminating the main stem and branches; spikes mostly 2-10 cm long, elongating as flowering progresses upward from the base; bracts lance-subulate, mostly 2-3 mm long. Flowers numerous, small, dark blue to purple, slightly irregular; calyx tubular, unequally 5-toothed, 1.5-3 mm long, strigulose; corolla 5-lobed, salverform, weakly bilabiate, surpassing the calyx by 2-5 mm, the limb 2-4 mm across, the tube strigulose; stamens included; style slender, exserted from the calyx after flowering, 2-lobed at the tip, ovary superior, 4-celled, shallowly 4-lobed. Fruit oblong, 4-angled, splitting lengthwise into 4 nutlets, these ca. 2 mm long. Jul--Sep. Wet meadows, shores, stream banks, ditches and springs, where water is fairly fresh; common in all but extreme w ND, e MT, nw SD and e WY; (N.S. to B.C., s to FL and AZ).
Verbena hastata, with enlargement of a flowering spike. |
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