Description

Key Characters:

Growth Form: Annual or perennial herbs, often somewhat woody at base.

Stems: Stems decumbent, sometimes ascending, or occasionally subscandent, usually 3–10 dm long, densely soft short–villous, becoming glabrate.

Roots:

Leaves: Leaves simple. Opposite. Blades broadly ovate to rhombic–ovate or occasionally ovate–deltate, 1–6 cm long, 1–3 cm wide. Apex acute to obtuse. Base broadly cuneate or occasionally truncate. Upper surfaces sparsely scabrid to glabrous; lower surfaces sparsely puberulent to glabrate. Margins crenate–serrate. Petioles 0.7–1.5 cm long. Stipules absent.

Flowers: Flowers 2–6 in diffuse racemose inflorescences, bracts ovate, 1.5–2.5 mm long, apex acuminate. Calyx bilabiate, tubular to campanulate, 2-3 mm long, only slightly cleft, moderately glandular pubescent, 10–15–nerved, upper lip truncate or obscurely 3-toothed, lower lip 2-toothed, sometimes the teeth and lips obsolete. Corolla blue, strongly bilabiate, tube straight or curved, ca. 2.5 mm long, upper lip concave, ca. 1.5 mm long, lower lip spreading, 3-lobed; nectary disk often present at base of ovary, annular or developed on anterior side only. Stamens 2, scarcely exserted beyond or included in corolla tube, , aligned with the sinuses; anthers dithecal, opening by longitudinal slits, with an elongate connective articulated near the center of the filament; anther sacs at each end, sometimes lower anther sac or entire lower arm of connective rudimentary. Ovary superior, 2-carpellate; ovules 1 per ovary lobe, placentation basal-axile; style 1; stigmas 2.

Fruit: Nutlets narrowly obovoid; only one nutlet developing; ca. 1.5 mm long. Seeds with endosperm absent or scanty and oily.

Ploidy:

Habitat: Naturalized in low elevation; dry to wet; disturbed habitats.

Elevation Range: 0–1,000 m.