This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Herbs or shrubs, with alternate mostly entire and petioled leaves, and small blue or white flowers, in scorpioid spikes, or scattered. Calyx-lobes or -segments lanceolate or linear. Corolla salverform or funnelform, naked in the throat, its tube cylindric, its lobes imbricated, plicate or induplicate in the bud, spreading in flower. Stamens included; filaments short, or none. Style terminal, short or slender; stigma conic or annular. Fruit 2-4- lobed, separating into 4 1-seeded nutlets, or into 2 2-seeded carpels. Ovary entire, or 2-4-grooved. [Greek, sun-turning, i. e., turning to or with the sun.]
About 125 species, widely distributed in warm-temperate and tropicai regions. Besides the following, some 10 others occur in the southern and western parts of North America. The species are called Turnsole. Type species: Heliotropium europaeum L.
Fruit 4-lobed, each lobe becoming a 1-seeded nutlet. Flowers in scorpioid spikes.
Plant rough-puberulent; leaves oval.
1. H. europaeum.
Glabrous, fleshy; leaves linear to spatulate.
Leaves linear to oblanceolate; corolla 2" broad.
2. H. curassavicum.
Leaves broadly spatulate; corolla 3"-4" broad.
3. H. spathulatum.
Flowers solitary, terminating short branches.
4. H. tenellum.
Fruit 2- lobed, or of 2 carpels.
Style elongated; flowers large, scattered, white.
Style very short; flowers blue, in scorpioid spikes.
6. H. indicum.
Heliotropium europaeum L. Sp. Pl. 130. 1753.
Annual, much branched, rough-puberulent, 6'-18' high. Leaves oval, 1'-2' long, obtuse at the apex, narrowed at the base, slender-petioled, pinnately veined; flowers white, 1"-2" broad, in dense 1-sided scorpioid, bractless spikes; terminal spikes in pairs, the lateral ones commonly solitary, becoming 1-3' long in fruit; calyx-segments lanceolate to linear-lanceolate, shorter than the corolla-tube; anthers distinct, obtuse; stigma-tip long-conic; fruit depressed-globose, pubescent, 4-lobed, at length separating into 4 nutlets.
In waste places, Massachusetts to New York, Pennsylvania and Florida. Adventive or naturalized from Europe. June-Oct.
Heliotropium curassavicum L. Sp. Pl. 130. 1753.
Annual, fleshy, glabrous throughout, more or less glaucous, branched, diffuse, the branches 6'-18' long. Leaves linear, or linear-oblong, entire, very inconspicuously veined, 1-2' long, 11/2 - 3" wide, obtuse at the apex, narrowed into petioles, or the upper sessile, sometimes with smaller ones fascicled in the axils; scorpioid spikes densely flowered, bractless, mostly in pairs; flowers about 2" broad; calyx-segments lanceolate, acute; corolla white with a yellow eye or changing to blue; stigma umbrella-shaped; anthers acuminate; fruit globose, at length separating into 4 nutlets.
On sandy seashores, Delaware to Texas and Mexico. Widely distributed in saline and maritime soil in the West Indies, South America and the Old World. In ballast about the northern seaports. May-Sept.