Larkspur (Delphinium (Belladonna Group) 'Casablanca')

Overview

Delphinium (Belladonna Group) ‘Casablanca’ offers spectacular vertical accents in the garden, celebrated for its towering spikes of pure white blooms that appear from May through July. This vigorous selection is part of the Belladonna Group, which means it often performs better in warmer conditions than some traditional hardy types, though it still requires care in hot summers. As an excellent cut flower, Larkspur brings sophisticated structure and color deep into floral arrangements.

Cultivating this herbaceous perennial successfully requires attention to detail, particularly concerning soil drainage and wind protection, as it demands a high maintenance input. Delphinium (Belladonna Group) ‘Casablanca’ rewards dedicated gardeners with its showy display, making it a definitive feature when placed correctly toward the back of a border. Gardeners seeking dramatic vertical interest should consider this specific white cultivar for its strong performance potential outside of the hottest, most humid environments.

Fast Facts

• Plant Family: Ranunculaceae
• Plant Type: Herbaceous perennial
• Hardiness Zones: USDA Zones 3-7
• Size at Maturity:
  • Height: 2.5-3 ft
  • Spread: 1-2 ft
• Bloom Time: May to July
• Bloom Description: White
• Sun Exposure: Full sun
• Water Needs: Medium
• Maintenance Level: High

How to Grow

Plant Delphinium (Belladonna Group) ‘Casablanca’ in the spring or fall in locations offering full sun. The key to success for this Larkspur variety is the soil: it must be fertile, humus-rich, medium moisture, and crucially, well-drained. This plant tolerates alkaline soils well, which is a bonus for many garden sites.

Water requirements are medium; ensure consistent moisture, especially during dry spells, but never allow the crowns to sit in standing water, which invites rot. Plants appreciate cool summer temperatures and may need partial afternoon shade in the hottest climates. Due to their height, Delphinium (Belladonna Group) ‘Casablanca’ requires protection from strong winds and heavy rains, necessitating staking or placement near a supportive structure like a fence.

Prompt deadheading is essential for maximum return. After the main flush of bloom fades between May and July, immediately cut the spent flower spikes back down to the basal foliage. This critical pruning step often encourages a secondary, though usually smaller, bloom period much later in the summer or into the fall.

Landscape Uses

Delphinium (Belladonna Group) ‘Casablanca’ excels when used to create drama and height in the landscape. Its upright structure makes it superb in cottage gardens, where it blends well with softer textures, or positioned at the back of mixed borders to provide a crisp backdrop. Massing this white Larkspur cultivar or planting it in thoughtful groupings maximizes the impact of its tall flower spikes.

For wind protection, a classic design technique mentioned is planting this vigorous selection against a sturdy stockade fence. Though deer generally leave this plant alone, it thrives alongside other sun-loving perennials that appreciate rich soil, such as roses or tall phlox. The fact that ‘Casablanca’ produces excellent, sturdy stems makes it an indispensable choice for gardeners who regularly harvest flowers for indoor enjoyment.

Standout Features

Flower Qualities

• Showy
• Good Cut

Noteworthy Characteristics

Delphinium is a genus consisting of over 300 species of annual, biennial and perennial flowering plants. Most delphiniums sold in commerce today are complex hybrids. One such hybrid grouping, commonly known as English hybrid types or Elatum Group (often designated as Delphinium x elatum), features a large number of showy cultivars which have been introduced into commerce over time in a number of different series or strains which are considered by many gardeners to contain some of the showiest of the delphiniums available in commerce today.Genus name comes from the Greek word delphis meaning dolphin in reference to the flower bud shape of some species purportedly resembling a dolphin.‘Casablanca’ is a white flowering cultivar in the Belladonna Group, which is made up of several hybrid cultivars resulting from crosses of Delphinium elatum, D. Cheilanthum and D. Grandiflorum. The members of this group are said to have superior performance in hot, humid climates. An upright, vigorous selection, ‘Casablanca’ produces numerous flowering stalks up to 3’ tall with showy, white blooms. An excellent cut flower. The sturdy stalks may not require staking, especially if placed in a full sun location protected from wind.

Tolerances

• Deer

Potential Problems

Delphiniums require considerable maintenance (staking, pruning, deadheading, disease control) in order to perform well in the garden. Delphiniums are generally susceptible to powdery mildew, botrytis blight, leaf spots and crown rot. To minimize fungal issues, always water plants at the base to avoid wetting the foliage, and aim for full sun exposure, which improves air flow and resistance to mildew.

Crown rot is an inevitable consequence of poorly drained soils or planting the crown too deeply; amending soil structure is crucial for long-term health. Slugs and snails can chew unsightly holes in the foliage, requiring vigilance when new growth emerges. Gardeners should also scout regularly for common pests like aphids, leaf miners, stem borers, and mites, treating outbreaks promptly to keep the showy white spikes pristine. Remember that this species of Larkspur is considered toxic to humans if ingested.

Frequently Asked Questions

What hardiness zones is Larkspur suitable for?

Delphinium (Belladonna Group) ‘Casablanca’ is winter hardy across USDA Zones 3 through 7.

How large does Delphinium (Belladonna Group) ‘Casablanca’ grow?

This variety typically reaches heights between 2.5 and 3 feet tall, with a spread of 1 to 2 feet wide.

When does Larkspur bloom?

This white-flowering cultivar has its main bloom period lasting from May into July.

What sun exposure does Delphinium (Belladonna Group) ‘Casablanca’ need?

This plant performs best when situated in a location receiving full sun, though a little afternoon relief is appreciated in very hot summers.

Conclusion

The striking verticality and clean white coloring of Delphinium (Belladonna Group) ‘Casablanca’ make it an indispensable plant for adding architectural height and elegance to summer flower displays. While this Larkspur demands higher maintenance, its value as a showy perennial and superb cut flower justifies the attention required. Before planting, carefully assess your summer climate and ensure you can provide staking and rich, well-drained soil to ensure a magnificent seasonal performance.

Design Ideas for Vertical Interest

Strategically placing tall, structural plants like this white Larkspur creates dynamic visual lines throughout the garden narrative. Use ‘Casablanca’ to break up low, mounding perennials or to add necessary height against solid structures like fences or walls where wind buffering is naturally provided. Groupings of three or five spikes create the most noticeable impact, drawing the eye upward toward the sky.

When designing a white-themed garden, pair Delphinium (Belladonna Group) ‘Casablanca’ with silver-leaved foliage like Lamb’s Ears (Stachys byzantina) or silvery Artemisia. The contrasting textures—the feathery foliage below and the clean spikes above—enhance the perceived whiteness of the blooms, creating a sophisticated, cool-toned effect that carries well across a distance.

Companion Planting Considerations

Because Delphinium (Belladonna Group) ‘Casablanca’ requires fertile, consistently moist yet well-drained soil supplemented with calcium (as it performs well in alkaline soils), companion plants should share these preferences. Roses thrive under similar soil rich conditions and bloom concurrently, providing beautiful color massing around the base of the taller Larkspur.

Other excellent companions include Nepeta (Catmint), whose fine texture and blue-purple flowers contrast beautifully with the white spikes, and sturdy, compact Geraniums that can cover the lower soil level, helping to keep the base of the delphinium cool and shaded. Avoid siting it near aggressive spreaders as the high maintenance needs of the delphinium require easy access for staking and deadheading.