1. Verbena bonariensis L. (South American vervain)

Map 2684

Plants annual (perennial farther south). Stems 60–150(–250) cm long, stiffly erect with ascending branches, strongly 4-angled, moderately to densely pubescent with a mixture of gland-tipped and nonglandular, spreading to ascending hairs, usually strongly roughened to the touch. Leaves sessile, the blades 2–10(–15) cm long, narrowly lanceolate to narrowly oblong, narrowly oblong-lanceolate, or narrowly oblong-elliptic, often slightly narrowed toward the base, but with small auricles and noticeably clasping the stem, rounded or more commonly angled to a bluntly or sharply pointed tip, the margins finely and often irregularly toothed, sparsely to moderately pubescent on the upper surface with stiff, loosely ascending, sometimes pustular-based hairs, the undersurface densely pubescent with a mixture of finer gland-tipped and nonglandular hairs. Inflorescences dense clusters of spikes, 0.5–2.0(–4.0) cm long, short and broad, usually appearing as globose or headlike clusters, not elongating much with age. Bracts 2.5–4.0 mm long, slightly shorter than to slightly longer than the calyx, narrowly lanceolate to narrowly triangular. Calyces 2.0–3.5 mm long. Corollas 5–8 mm long, the outer surface densely hairy, narrowly trumpet-shaped, sometimes nearly tubular, purple to purplish blue, the tube slender, the limb 1.5–3.0 mm in diameter. Nutlets 1.3–2.0 mm long, narrowly oblong in outline, the inner surface usually pale and with dense, minute papillae, the outer surface brown, with several longitudinal ridges, these with a few cross-ridges toward the tip. 2n=28. April–October.

Introduced, known thus far only from the city of St. Louis (native of South America, introduced sporadically in the U.S. mostly in southern states and Hawaii; also Caribbean Islands, Australia, New Zealand). Open disturbed areas.

This common garden species was first collected as an escape in Missouri by the author in 2002.