The Candle Larkspur (Delphinium elatum) is a perennial herbaceous plant belonging to the Ranunculaceae family, widely cultivated for its ornamental flowering, especially in temperate climates. Although native to the alpine regions of Central Europe and Western Asia, spontaneously appearing in moist meadows and mountainous areas, modern cultivars result from a lengthy process of genetic improvement and interspecies hybridization.
The development of garden larkspurs began in the 19th century in Western Europe, where horticulturists initiated crosses between different species of the genus Delphinium aiming for larger flowers, more intense colors, and greater disease resistance. In the 20th century, breeding programs were expanded in the United States, Japan, and New Zealand, consolidating a group of highly ornamental hybrids known for their stateliness and diversity of forms and colors.
Contemporary cultivars are classified into two main groups: Elatum Group and Belladonna Group. The Elatum Group, which includes Delphinium elatum, is the most representative and popular, consisting mostly of tetraploid hybrids derived from D. elatum, although other species, such as D. cardinale, have been used in crosses to introduce new characteristics. These plants are notable for their tall stature, dense inflorescences, and abundant blooms, along with a wide variety of colors. Meanwhile, the Belladonna Group comprises mainly hexaploid hybrids between D. grandiflorum and D. elatum, featuring a lower stature and a more open growth habit.
The genus name Delphinium is derived from the Greek ‘delphis,’ meaning dolphin, due to the resemblance of the flower bud to the snout of this animal. The epithet ‘elatum’ comes from Latin meaning ‘elevated’ or ‘tall,’ referring to its remarkable height, which can exceed six and a half feet (two meters) in vigorous cultivars.
Delphinium features an upright, herbaceous, and robust stem, with elongated internodes and a slightly grooved texture. The stems generally do not branch, supporting terminal inflorescences at the apex. The base of the plant forms a clump with a short rhizome and fibrous roots, which store reserves for annual vegetative growth. It is a plant that dies back to the ground in winter, resprouting in spring with renewed vigor.
The leaves are alternate, long-petioled, with palmatissect blades, deeply lobed into 5 to 7 segments. The texture of the leaves is fine and delicate, with a medium green color on the upper side and lighter on the underside. The leaf margin is serrated, and the surface can be either glabrous or slightly pubescent, depending on the cultivar.
The inflorescence is a terminal, erect raceme, which can contain dozens of flowers arranged spirally along a robust floral axis. Each flower is hermaphroditic, zygomorphic, and features five petaloid sepals, of which the uppermost forms a characteristic spur. Inside, there are four true petals, with the upper two also spurred, enclosed by the sepals. The flowers can be single, semi-double or double, in shades of blue, violet, white, pink, and less commonly, red. Blooming generally occurs during the summer.
Pollination is carried out by large bees, such as those from the genus Bombus, and butterflies with long proboscises, which are able to access the nectar contained in the spurs. The fruit is an aggregate of three to five follicles, which open longitudinally upon maturing, releasing small, black, and rough seeds, responsible for the natural propagation of the species.
Numerous series and cultivars of Delphinium elatum have been developed to enhance ornamental characteristics, such as plant height, flower coloration, and disease resistance.
Among the most popular series, the following stand out:
- Magic Fountains: This series is known for its medium-sized plants, reaching about 35 to 47 inches (90 to 120 cm) in height, with flowers in a variety of colors, including blue, lavender, pink, and white.
- Pacific Giant: Characterized by tall plants, reaching between 4.9 to 5.9 feet (1.5 to 1.8 meters) in height, with large and showy flowers in shades of blue, purple, pink, and white.
- Dwarf Pacific: Features compact plants, ideal for smaller gardens, with heights ranging from 24 to 35 inches (60 to 90 cm), and flowers in various colors.
- New Millennium: Developed in New Zealand, this series is recognized for its robustness and the wide range of flower colors, including rare hues like red and salmon.
- Aurora: Includes six distinct varieties: Blue, Deep Purple, Lavender, Light Blue, Light Purple and White, all with semi-double flowers and strong stems, reaching about 47 inches (1.2 meters) in height.
- Guardian: This series includes hybrids of the Pacific Giant, known for their early blooming in spring and re-blooming in late summer. The plants reach between 24 to 35 inches (60 to 90 cm) in height and feature flowers in shades of blue, lavender, and white.
- Highlander: Originating from Scotland, this series is notable for its double and semi-double flowers in a variety of colors, including blue, pink, and white. The plants grow between 24 to 47 inches (60 to 120 cm) in height and are valued for their robustness and aesthetic appeal.
- Delphina: This series features dwarf cultivars, ideal for smaller gardens or container growing. The plants reach about 14 to 18 inches (35 to 45 cm) in height and produce double flowers in colors such as light blue with a ‘white eye,’ known for their resilience and no need for staking.
Some specific Delphinium cultivars have also received the prestigious Award of Garden Merit from the Royal Horticultural Society, in recognition of their exceptional performance in gardens. Among them are:
- ‘Lord Butler’: This cultivar stands out for its light blue flowers with a white “eye” in the center, forming dense, erect inflorescences.
- ‘Sungleam’: Features cream-yellow flowers, an unusual color for delphiniums, with semi-double petals and vigorous growth.
- ‘Sweethearts’ (New Millennium Series): Part of the New Millennium series, this cultivar has medium pink flowers with a white “eye”, combining beauty and resilience in a medium-sized plant.
- ‘Spindrift’: This medium-sized variety has semi-double pale lilac flowers with a white-cream center.
- ‘Blue Dawn’: A medium-sized cultivar, reaching up to 7.2 feet (2.2 meters) in height, with pale blue flowers with a pinkish hue and a small black center.
- ‘Faust’: Known for its imposing floral stems that can reach 5.9 feet (1.8 meters) in height, this cultivar displays semi-double deep blue-purple flowers with a black “eye”.
Delphinium was formally described by Carl Linnaeus in his work Species Plantarum, published in 1753, which marks the beginning of modern botanical nomenclature. Its inclusion in Species Plantarum demonstrates that Delphinium elatum was widely recognized and cultivated in the eighteenth century, not only for its beauty but also for its botanical value.
In addition to its ornamental value, it is essential to note that all parts of the plant, especially the seeds and roots, contain toxic diterpenoid alkaloids, such as delphinine. Despite the toxicity, compounds extracted from the plant have historically been used in herbal medicine and the preparation of traditional remedies in some European cultures, always with great caution and under strict control.
Delphinium is often mentioned as a symbol of boldness, ephemeral beauty, and renewal. In Victorian flower symbolism, Delphinium represents feelings of ardor and an open heart, being used in floral arrangements that express sincerity and emotional intensity. The presence of Delphinium in historical gardens and botanical paintings of the nineteenth century reinforces its reputation as one of the most majestic flowers of the European summer.
In landscaping, Delphinium elatum is valued for its dramatic vertical architecture, serving as a focal element in mixed beds and borders. Its imposing stature makes it ideal for planting at the back of flower beds, providing depth and contrast. It can be used in formal, English, or cottage-style gardens, harmonizing with medium to small plants that soften its base, such as Alchemilla mollis, Nepeta faassenii, and Geranium bohemicum. These combinations balance the verticality of the Delphinium with dense, textured plants, creating movement and visual variety in the beds.
Delphinium is also widely used as a cut flower, especially in hybrid varieties developed for commercial purposes. Its long, sturdy, and blooming stems allow for compositions in vertical bouquets and monumental arrangements for events, weddings, and interior decoration. The post-harvest durability, especially when harvested at the beginning of anthesis, is valued in florists and botanical studios. Cultivation for this purpose requires special attention to fertilization, staking, and pest control, as the uniformity of the stems and the integrity of the flowers are critical for commercial value.
In addition, Delphinium elatum can be explored in wildflower and pollinator gardens, contributing to biodiversity and attracting beneficial insects. In sustainable garden projects, it can be integrated with ornamental grasses, creating a contrast between the rigid lines of the Delphinium and the fluid movement of the grasses. The predominant blue-violet coloration of the flowers also allows for monochromatic or complementary harmonizations, composing sophisticated chromatic schemes in high-standard landscape projects.
The Candle Larkspur is a light and climate-demanding plant, which ideally grows under full sun, receiving at least six hours of direct sunlight daily. In regions with very hot summers, it can tolerate partial shade during the afternoon, especially if accompanied by good ventilation and soil moisture. The species prefers temperate and cool climates, with ideal temperatures ranging between 50°F (10°C) and 77°F (25°C). Although it withstands frosts, it is sensitive to intense and prolonged heat, showing signs of thermal stress in arid or tropical environments.
The ideal soil for Delphinium elatum should be fertile, deep, light, well-drained, and rich in organic matter. Clay soils should be amended with the addition of organic compost to ensure good root aeration. The soil pH should be between 6.0 and 7.5. For pot cultivation, a balanced substrate composition is recommended, using equal parts garden soil, perlite, and organic compost, ensuring good moisture retention without waterlogging the roots. Drainage is crucial, necessitating holes at the bottom of the pot and a layer of draining material such as gravel or expanded clay.
Planting Delphinium can be done using either ready-grown seedlings or seeds. For garden planting, it is recommended to space plants 16 to 24 inches (40 to 60 centimeters) apart, ensuring adequate ventilation and prevention against fungal diseases. Watering should be regular, keeping the soil consistently moist but not waterlogged. In periods of intense heat or wind, an increase in irrigation frequency may be necessary. Drip irrigation or at soil level is preferable to prevent wetting the leaves and flowers.
Fertilization should be balanced, with an emphasis on phosphorus and potassium to encourage blooming and strengthen the plant’s structure. During the vegetative cycle, organic fertilizer or NPK 10-10-10 formulations should be applied biweekly. In the pre-blooming phase, switching to a formulation like NPK 4-14-8 promotes abundant flowering. After blooming, fertilization should be gradually reduced, following the plant’s natural cycle.
For cultivars with tall stature and long floral stems, staking is essential. This should be done early in the plant’s development, using bamboo stakes, wood, or metal structures fixed next to the base. Ties should be firm yet not constrictive, allowing growth and support during blooming. Pruning of wilted flowers stimulates new blooms and prolongs the ornamental cycle, while cleanup pruning, removing yellowed or damaged leaves, enhances ventilation, improves plant appearance, and prevents disease onset.
Candle Larkspur tolerates moderate frosts and negative temperatures once established, as long as the soil does not remain waterlogged. Delphinium exhibits low tolerance to drought, being sensitive to lack of moisture, especially during the formation of inflorescences. It also does not adapt well to regions with intense and dry heat. Although it can withstand light winds, its floral stems are susceptible to breakage under strong winds, requiring reinforced protection or staking. It is not suitable for coastal regions, as soil salinity and salty wind can impede its growth.
Delphinium may be affected by slugs and snails that attack young leaves and shoots. Control can be managed with physical barriers or specific baits. Additionally, Delphinium might suffer from infestations of aphids and mites, particularly under conditions of heat and low moisture. Fungal diseases such as mildew, powdery mildew, and root rot are common in poorly ventilated environments or with waterlogged soil. Preventive control includes appropriate spacing, correct watering, and the use of biological fungicides or copper-based products. Crop rotation and cleaning of plant debris also help in preventing infections.
Propagation by seeds is the most traditional and effective method. The seeds must undergo a cold stratification process, which simulates natural winter conditions, promoting dormancy break. This stratification involves storing the seeds in slightly moistened substrate, inside closed plastic bags or covered trays, kept in a refrigerated environment at about 36°F to 41°F (2°C to 5°C) for a period of two to three weeks. After this period, sowing is carried out in trays or seedbeds with a light, well-drained substrate rich in organic matter. At this stage, Delphinium benefits from protected cultivation, avoiding frosts or sudden drops in temperature that can still occur in early spring.
Germination occurs between 14 and 21 days, under a constant temperature of about 55°F to 61°F (13°C to 16°C). After the formation of three to four pairs of true leaves, and when there is no longer a risk of frost, the seedlings can be transplanted to larger pots or directly to the definitive flower beds. Flowering generally occurs in the second summer after sowing, although more precocious cultivars may bloom even in the first year, when sowed in late winter or early spring.
Division of clumps is a practical alternative to maintain genetic uniformity and accelerate the production of plants capable of flowering in a short span of time. This method is performed at the end of winter or the beginning of spring, before intense sprouting.
With the help of a sharp and sterilized tool, the mother plant is carefully unearthed and divided into segments with at least one or two growth buds and well-formed root portions. Each division should be replanted immediately in previously prepared soil, with abundant irrigation in the first weeks to facilitate rooting.
In subtropical climates, propagation by seeds should be adapted to avoid the effects of excessive heat, especially during the initial stages of development. In these cases, sowing should be scheduled for autumn, avoiding the high temperatures of summer. Stratification may still be necessary, although some adapted cultivars may germinate without this stimulus. Trays should be kept in shaded and cool locations, with adequate ventilation and light mist irrigation to prevent the potting mix from drying out. Transplanting to the final location should be done in winter, during periods without heavy rainfall, to allow establishment before the spring heat.
