3. Heliotropium indicum L. (turnsole, Indian heliotrope)

Tiaridium indicum (L.) Lehm.

Pl. 426 i–k; Map 1904

Plants annual, with a slender taproot. Stems 20–60(–80) cm long, erect to moderately ascending, sparsely to moderately pubescent with usually a mixture of longer, stiff, spreading, mostly pustular-based, nonglandular hairs and shorter, softer, spreading to loosely appressed, nonglandular hairs. Leaves usually alternate toward the stem base and opposite above, sometimes all mostly alternate or opposite, moderately to long-petiolate, the petiole usually winged toward the tip. Leaf blades 4–8(–12) cm long, 20–70 mm wide, herbaceous (not succulent), broadly ovate to oblong-ovate or triangular-ovate, abruptly tapered at the base, angled or tapered to a bluntly or sharply pointed or rarely rounded tip, the margins entire to somewhat scalloped, wavy, or with a few coarse, blunt teeth, the surfaces sparsely to moderately pubescent with fine, short hairs mostly along the veins, sometimes also with sparse longer, bristly hairs along the main veins toward the leaf base. Inflorescences terminal, solitary or rarely paired scorpioid spikes, these sessile or on a stalk to 2 cm long, densely flowered, lacking bracts. Calyces 1.5–3.0 mm long, the lobes linear to narrowly oblong-lanceolate, moderately to densely pubescent with stiff, loosely appressed, nonglandular hairs, more or less spreading after the fruit has dispersed. Corollas 2–4 mm long, 2–4 mm in diameter (measured across the spreading lobes), trumpet-shaped, blue to purplish blue, usually with a yellow to white spot at the base of the lobes, hairy on the outer surface, the tube 1–2 mm long, glabrous on the inner surface, the lobes 1.0–1.5 mm long. Stamens attached at the base of the tube, the anthers 0.5–0.8 mm long. Stigma on a short style, the sterile appendage short-cylindrical (about as long as wide) to slightly tapered, more or less truncate and minutely notched at the tip, glabrous. Fruits 2.5–4.0 mm long, 3–5 mm wide, appearing strongly 2-lipped above a more or less globose body, with 2, divergent, flattened lobes at the tip, glabrous, splitting into 2 pairs of nutlets, these sometimes breaking apart with age into 4, 1-seeded nutlets. Nutlets with the dorsal surface having 1 or 2(3) prominent longitudinal ridges, light brown ventrally with greenish brown to yellowish brown lobes and dorsal surface. 2n=22, 24. August–October.

Scattered mostly south of the Missouri River, most abundant in the Mississippi Lowlands Division (native range uncertain but probably tropical South America; introduced nearly worldwide, mostly in tropical and warm-temperate regions; in the U.S. from New York to Florida west to Kansas and Texas). Banks of streams and rivers, margins of ponds, lakes, sinkhole ponds, and sloughs; also crop fields, fallow fields, ditches, farmyards, railroads, roadsides, and open disturbed areas.

This attractive species is distinguished by its thick, hollow stems, leaves that often appear somewhat wrinkled, elongate scorpioid spikes with dense, blue to purple flowers along the upper side, and oddly shaped fruits.