Certain plants bring to mind bygone days, and are endowed with an aura of nostalgia. Typical examples are mignonette, Mimulus, verbena, certain old-fashioned roses, some of the no longer cultivated carnations, and heliotrope. Although still cultivated, heliotrope remains an old-fashioned plant, often grown in pots for sentimental reasons, and more popular in cottages than in modern gardens where tradition is not considered in the over-all planting plan. The plants are always modest in appearance and subdued in color. Vilmorin refers to heliotropes as “not noted for their form, nor for their color”, but the plants are always pleasing and the flowers have their own inimitable fragrance.
Nowadays, with the orgy of color to be found in our gardens, we have somewhat forgotten that to be really complete a flower should have fragrance as one of its characteristics. A rose without scent is only half a rose; and as for many of the modern carnations and sweet peas, the less said about their scent the better. The heliotrope’s principal attraction is its fragrance, and it is generally grown exclusively for that purpose; more frequently it is grown as a pot plant than in the garden, although it is an excellent subject for summer bedding. As pot plants they can be kept for several years, and even trained as standards. Of the quality of the perfume, Fletcher says it is “strong and reminiscent of hawthorn”. Other writers compare the scent of Heliotropium corymbosum to that of narcissus, that of Heliotropium peruvianum to vanilla, while the fragrance of Heliotropium suaveolens has been compared to vanilla and apples. Heliotropium peruvianum and Heliotropium corymbosum are, however, now considered synonyms of Heliotropium arborescens; a change that once again confirms that the nose is one of the most personal sensory organs we possess; registering the same fragrance in different ways for different people. The British, however, have even more personal ideas about the fragrance of heliotrope; they call it Cherry Pie to indicate that the perfume of the flowers is similar to that of a freshly baked cherry pie, and they are certainly not mistaken.
In Greek heliotropin means “turning with the sun”; but, as in the case of sunflowers, this is a false description. We do not know if our heliotrope is the Heliotropium of the ancients because the plant mentioned by Pliny, which he named Clythia, had blue flowers, while the original Heliotropium was supposed to have white flowers. We know little of the contacts the Greeks may have had with the mysterious East, nor do we know if heliotropes reached the Orient by way of Africa or by way of the Atlantic, before reaching Greece.
Whether our present-day heliotropes can be identified with that of ancient times or not, it has long enjoyed popular favor in Europe. It has also been used in folk medicine, and in some places is still employed as an astringent, and valued for its tannic and other properties.
Heliotropium arborescens was discovered in Peru in 1740, and imported to Paris by Jussieu. The plant immediately found favor and rapidly became popular for flower arrangements. The plant was named Herbe d’amour (plant of love).
There are more than 250 species of genus Heliotropium, mostly diffused throughout the hottest parts of the world; many are annuals. The heliotrope cultivated in gardens is Heliotropium arborescens L. (syn. Heliotropium peruvianum, Heliotropium corymbosum), and its several varieties. The two European species are Heliotropium supinum, a sub-shrubby, white-flowered, scentless type that is frequently found in seaside localities; and Heliotropium europaeum, white-flowered and sometimes graced with a faint, elusive scent. Neither species, however, has any garden value.
Cultivation. In northern countries Heliotropium arborescens must be grown as a greenhouse plant and protected against even the slightest frost. It is, in fact, about as tender as the so-called geranium (Pelargonium zonale). The delicious and characteristic fragrance of the flowers is most pronounced in the early morning, before sunrise, and in the evening towards sunset. To increase the intensity of the perfume the plants should be given only the minimum amount of water needed to keep them alive. It is easily cultivated, with no particular demands, but it prefers a soil rich in humus such as would be used for fuchsias and cyclamens. Heliotropes are equally happy in acid or alkaline (calcareous) soils, and are excellent subjects for seaside localities; but they should always be given an open, warm, sunny position. Old plants can be grown in pots for several years if the surface soil is changed every spring and if weekly applications of liquid organic fertilizer are given during the growing season. Some years ago, it was the fashion to train the plants in the form of standards; removing all the lateral shoots so as to form a clean trunk and then finally allowing the terminal branches to develop so they assumed a good head with semi-pendulous branches. If grown permanently in a greenhouse—where the plants will continue to bloom during the winter—the night temperature should not be in excess and the greenhouse should be spacious, light, and well ventilated.
Propagation is generally effected by means of seed, but unfortunately the degree of fragrance can vary from seedling to seedling, and suppliers do not offer any guarantee. The ideal method of propagation, when a plant with strongly fragrant flowers has been located, is to propagate by means of cuttings.
Seed should be sown in a warm greenhouse in February-March, pricked out when ready, and then potted individually into small fibre pots, repotting as the plants develop. The plants can be planted in their flowering positions outside when all risk of frost has passed (or repotted into larger pots if destined for pot cultivation). Germination is not always good and is frequently capricious.
Cuttings can be taken at almost any time between late spring and early autumn (or even in winter in a greenhouse). The best rooting medium is a compost made up of half peat and half sand. They should be kept in a closed greenhouse or heated frame, or under a glass bell-jar or transparent plastic, at a temperature of about 55°F. Cuttings taken late in the season should be of half-ripened wood, while those taken in spring or early summer should be made from soft new growths. If cuttings are to be taken from established pot- grown plants these should be first kept in a warm greenhouse for a few weeks to encourage the .production of suitable young growths. Soft cuttings generally take about two weeks or so to root, and care must be taken that they receive sufficient ventilation as they have a tendency to damp-off if there is an excess of moisture or a stagnant atmosphere. When rooted, the young plants can be potted and should be treated in the same manner as the seedlings.
Heliotropes appreciate an abundance of plant food during their period of active growth. This is best supplied by means of liquid organic fertilizer prepared from dried blood, manure, or from one of the commercial brands available on the market. To produce bushy, well-branched plants, both the seedlings and young plants raised from cuttings should be topped times as they develop—preferably each time they are repotted.
Native to Peru. A semi-shrubby, semi-woody, herbaceous perennial with a wide-spreading erect habit. In a frost-free climate it can be kept in active vegetation for several years, developing a true woody stem. Bright-green leaves are alternate, short-stalked, oval-lanceolate, with a roughly crinkled upper surface and downy on the under- surface. The flowers are borne in small spikes grouped in largish corymbs. The calyx is small and persistent; the corolla and petals are lilac-blue or heliotrope, and the blooms are strongly fragrant with a vanilla scent. H. x voltarieanum has a compact habit with larger and richer green foliage than the species, and intensely blue flowers marked with white at the throat; it is even more delicate than the type. It is a hybrid believed to have been created at Volterra; if such is the case, it should be written volterrae. Another variety that at one time was very popular is var. Triomphe de Liege, with pale blue-grey flowers; it is easily raised from seed. There are also several named varieties with white or pink flowers that are available commercially.