Annual or perennial herb 40 cm - 1.5 m tall Stem: erect, branching near base, nearly hairless to minutely stiff-haired. Leaves: opposite, stalked, 5 - 20 cm long, more than 2 cm wide, egg-shaped and tapering to a pointed tip, coarsely toothed, nearly hairless to densely velvet-haired beneath. Inflorescence: a branched cluster of numerous spikes, each ascending spike less than 7 mm thick, with flowers well separated along the spike. Flowers: white, subtended by 0.5 - 1.5 mm long bracts that are egg-shaped with pointed tips and hairy along the margin. The calyx is 2 - 2.3 mm long, triangular-lobed, and hairy, and the corolla is barely longer than the calyx and has blunt lobes. Fruit: four nutlets surrounded by the persistent calyx but exposed at the top, each nutlet 1 - 2 mm long with a smooth and flat or wrinkled back.
Similar species: Verbena urticifolia and Verbena hastata have more than three flower spikes per cluster. Verbena hastata differs by its lance-shaped to narrow egg-shaped leaves and its bluish purple flowers that overlap along the spike. Verbena urticifolia is represented by two varieties in the Chicago Region. See links below for further information.
Etymology: Verbena is the Latin name for vervain. Urticifolia means nettle-leaved.
Author: The Morton Arboretum
From Flora of Indiana (1940) by Charles C. Deam
This species doubtless occurs in every county. It is found in almost all kinds of soil except in very wet places; it is generally found in open woods, along logging roads in thick woodland, in fallow fields and waste places, and along roadsides and railroads. All of the species of Indiana vervains are extremely variable, especially in the leaf margins and color of flowers. Evidence of hybridization is frequent. I have a specimen with pink flowers from Wells County.
Erect, single-stemmed annual or perennial, 4-15 dm, often branching from near the base; lvs broadly lanceolate to oblong-ovate, petiolate, 5-12 cm, coarsely and somewhat doubly crenate-serrate; spikes paniculately disposed, slender; bracts ovate, acuminate, ciliate; cal-teeth short, subequal; cor white, the tube scarcely exserted, the limb 2(-4) mm wide, the lobes obtuse; fr exposed at the top; nutlets
1-2 mm; 2n=14. Thickets, moist fields, meadows, and waste places; N.B. (?) and Que. to N.D., s. to Fla. and
Tex. June-Oct. Var. urticifolia, with the range of the sp., has the lvs hirtellous or glabrous on both sides, the
hairs whitish, 1-1.3 mm, the cal strigose, 2-2.3 mm at maturity, and the nutlets 2 mm, corrugated on the back.
Var. leiocarpa L. M. Perry & Fernald, with more restricted range, from Conn. and Pa. to N.D., S.C., and Okla., has the lvs densely velutinous with hairs to 0.3 mm, the mature cal puberulent, to 2 mm, the nutlets 1.5 mm, smooth. A hybrid with V. stricta is V. ةllicita Moldenke; one with V. hastata is V. إngelmannii Moldenke.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.