Fortunately, heliotrope makes both a striking mid-mourning hue and a scent-sational tender perennial. Discovered in the Peruvian Andes by French doctor and botanist Joseph de Juissieu, who journeyed to South America with a scientific expedition in 1735, the plant achieved almost immediate popularity after being introduced to Europe in 1751.
De Juissieu didn't make it back to Europe himself until twenty years later. Unfortunately, many of his other finds had been stolen or lost at sea, and the doctor ultimately descended into insanity--perhaps in despair over what he conceived a wasted life.
Despite all his years of botanizing, heliotrope (Heliotropium peruvianum, now known as arborescens) is the only find widely attributed to him. However, an 1889 book called The Pharmacology of the Newer Materia Medica by George S. Davis states that De Juissieu was the first explorer to send Erythroxylon coca--AKA cocaine--to Europe around 1750. If he could know how that turned out, I suspect he would prefer to be remembered as the discoverer of the herbe d'amour (flower of love) instead.
According to an 1855 edition of Philadelphia's The Horticulturist and Journal of Rural Art and Rural Taste, one of the newest heliotrope cultivars at that time was dubbed "Beauty of the Boudoir." Despite an occasional titillating name, the flower of love apparently never achieved the degree of infamy that blooms such as the camellia did. However, I suspect a lady had to be careful not to accept it from the wrong person.
Hardy in USDA zones 9 to 11, Heliotrope arborescens can grow into a 4-foot bush there, and bloom virtually all year round--or as long as the temperature remains above 40 degrees Fahrenheit anyway. As a summer annual in other zones, it usually doesn't have time to grow that large.
The plant bears clusters of small trumpet-shaped and 5-petalled flowers in shades of lavender, purple, and white. Often tinged with purple, the leaves appear so deeply veined as to look almost quilted.
Heliotrope can take full sun in cooler climates, but should have afternoon shade in hotter ones, with rich and well-drained soil which never dries out completely. Because it is a mountain plant, it seems to perform best in late summer and early fall when days turn cooler and less humid.
If you wish to start heliotrope from seed, sow it about four months before your last frost date, to give it the chance to achieve some height before being transplanted into the garden after all danger of frost is past. As the seeds are small, cover them only with the lightest sprinkling of seed-starting mix. The most widely available variety appears to be "Marine" or its dwarf variations, though some sellers of heirloom seeds offer plain old arborescens, which is anything but plain.
It germinated for me in five days and "Blue Wonder" in six days, but heliotrope can take as long as four to six weeks to sprout. The best fragrance reportedly comes from heirloom cultivars such as "Mrs. J. W. Lowther" or "Chatsworth," reproduced from cuttings of semi-ripe wood. As those are more available in Britain than here, you probably won't be too unhappy if you have to settle for spectacular new types such as "Black Beauty" instead.
You can keep your heliotrope as a houseplant by moving it indoors during the winter. Place it in a sunny spot--or under a grow light--where temperatures remain in the 50s, though the 60s will do. I've had plants last several years for me under grow lights in a cool back room, though they do eventually become woody and fade out. Although heliotrope blooms best when a bit pot-bound, I probably allowed mine to become pot-strangled!
The fragrance of the flowers is responsible for the plant's nickname of "cherry pie." Some will hold, however, that the scent is closer to almonds or vanilla. However delectable those blooms smell, don't be tempted to eat them, as all parts of the plant are poisonous. Since a Victorian gentleman would have given a lady heliotrope to signal his devotion to her, we might have to rewrite an old song to read, "Can she take a cherry pie, Billy Boy, Billy Boy?"
The Heliotropium arborescens photo is by Kurt Stuber, courtesy of Wikimedia commons and this license. The Heliotropium arborescens "Alba" photo is by poppysue and the Heliotropium arborescens "Black Beauty" photo by Kell, both from the Dave's Garden PlantFiles. The antique image is from the E. Step and D. Bois book, Favorite Flowers of Garden and Greenhouse, courtesy of plantillustrations.org. The thumbnail and the unidentified Heliotropium photo are my own.