Delphiniums: Majestic Spires for Every Garden

Delphiniums, the quintessential cottage garden flower, are renowned for their towering spikes of vibrant blooms. These stalwarts of the perennial border, traditionally associated with cool, English climates, have undergone a renaissance. Thanks to dedicated breeding programs, there is now a delphinium for almost every garden, regardless of size or climate.

From Towering to Tiny: A Delphinium for Every Space

Delphiniums offer a surprising range of sizes, from majestic 6-foot giants to petite 1-foot dwarfs. This allows gardeners to choose varieties perfectly suited to their space and design aesthetic. While traditionally associated with the back of the border, the introduction of smaller varieties means delphiniums can now take center stage in containers, smaller beds, or even as edging plants.

General Delphinium Information (Applies to most types):

• Description: Delphiniums are herbaceous perennials (with some exceptions when grown as annuals) known for their tall, showy flower spikes. Individual flowers are often spurred and can be single, semi-double, or double. The "bee" refers to the central cluster of small petals, which can be the same color as the main petals or contrasting. Foliage is typically deeply lobed and palmate.
• Details:
• Flower Colors: Blue, purple, pink, white, red, yellow (rare).
• Bloom Time: Late spring to mid-summer (depending on variety and climate). Possible rebloom in fall if deadheaded.
• Hardiness: Generally, USDA Zones 3-8, but best performance in Zones 3-6 or cool-summer areas of Zones 7 & 8.
• Toxicity: All parts of the delphinium plant are poisonous if ingested.
• Habitat: Delphiniums prefer cool, moist summers and mild winters. They thrive in full sun (at least 6 hours) in cooler climates but appreciate afternoon shade in hotter regions. Well-drained, fertile, slightly alkaline soil (pH 6.5-7.0) is essential.
• Landscaping Design Tips:
• Back of the Border: Tall varieties create a dramatic backdrop for other perennials.
• Cottage Gardens: A classic choice, adding vertical interest and color.
• Cutting Gardens: Excellent for cut flowers, providing long-lasting blooms.
• Mixed Borders: Combine with other perennials and annuals for a layered effect.
• Containers: Dwarf varieties are well-suited to containers.
• Vertical Accent: Use to create focal points in the garden.
• Mass Planting: Plant in groups of 3-5 for a greater visual impact.
• Planting and Care:
• Starting from Seed: Use fresh seed. Sow indoors in January/February for spring planting, or August/September for fall planting (especially in warmer zones).
• Planting: Choose a location with appropriate sun exposure. Amend soil with compost. Space plants 1-2 feet apart. Do not bury the crown.
• Mulching: Apply a 4–6-inch layer of organic mulch.
• Fertilizing: Side-dress with compost or a balanced fertilizer (e.g., 5-10-5) at planting, when flower stems form, and after flowering.
• Watering: Provide consistent moisture, especially during dry spells. Avoid overhead watering.
• Deadheading: Remove spent flower stalks promptly.
• Staking (for tall varieties): Use stakes and twine, cages, or linking stakes.
• Pest and Disease Control: Watch for slugs, snails, and powdery mildew.
• Winter Care: Mulch in very cold areas. Treat as annuals or choose heat-tolerant varieties in warmer zones.
• Dividing: Divide every 3 to 5 years, plants that live longer.

Delphinium Varieties by Size:

• Tall Delphiniums (4-6 feet): The Classic English Look These are the dramatic, eye-catching delphiniums that most people envision. They produce dense, impressive flower spikes in a range of colors, including blues, purples, pinks, whites, and even reds. They are ideal for creating vertical accents and adding a touch of grandeur to the garden. However, they generally require staking to prevent wind damage.
• Pacific Giants (Round Table Series): The most widely known tall hybrids, Pacific Giants boast large, 3-inch diameter, double flowers that are tightly packed on the stem. They require staking. Popular cultivars include:
• 'King Arthur': Striking royal violet flowers with a contrasting white "bee" (the central cluster of small petals).
• 'Black Knight': Deep, dark violet-blue flowers with a black bee, creating a dramatic, almost gothic effect.
• 'Galahad': Pure white flowers.
• 'Blue Bird': Mid-blue flowers with a white bee.
• New Millennium Hybrids (Dowdeswell's Delphiniums): Bred in New Zealand, these are a significant improvement over Pacific Giants. They offer:
• Superior Hardiness: More resistant to common delphinium diseases.
• Stronger Stems: Less prone to breakage and often do not require staking.
• Increased Heat Tolerance: A game-changer for gardeners in warmer climates.
• More Petals per Flower: Creating a fuller, more luxurious bloom.
• Wider Color Range: Including unique shades of pink and purple.
• DELPHINIUM 'Pagan Purples':
• Description: Deep, rich purple, semi-double to double flowers with a prominent bee (often black or striped).
• Details: Height: 5-6 feet. Strong stems. Excellent cut flower.
• Habitat: Standard Delphinium requirements. Benefits from the New Millennium hybrid hardiness.
• Landscaping: Back of the border, dramatic focal point.
• DELPHINIUM 'Purple Passion':
• Description: Another intense purple variety, often with a slightly ruffled appearance to the petals.
• Details: Height: 4-5 feet. May require staking in exposed locations.
• Habitat: Similar to 'Pagan Purples'.
• Landscaping: Excellent for adding depth and richness to the border.
• DELPHINIUM New Zealand 'Stars' series: The Delphinium New Zealand 'Stars' series is a popular and beautiful group of delphiniums. Here is a breakdown of key features:
• Variety of Colors: This series is known for its diverse color range, including white, pink, purple, and blue.
• Height: Plants in this series typically range in height from 3 to 6 feet, making them excellent for adding vertical interest to gardens. There are also "Mini Stars" which are a more compact variety.
• Breeding: These are English hybrid delphiniums, bred by New Zealand Delphiniums, and are the result of hand-crossed breeding to produce high-quality seeds.
• Characteristics: They are F1 hybrids, known for their strong stems, excellent form, and vigorous growth.
• They are selected for improved tolerance of heat and humidity, while retaining cold hardiness.
• Usage: They are popular for border plantings, cut flowers, and adding height to garden spaces. Due to the height of the standard variety, they often require staking to keep them upright. There are also "Mini Stars" that are a dwarf variety, which do not require staking.
• DELPHINIUM 'Blue Lace':
• Description: Sky blue, ruffled, Semi-double to double flowers with a small white bee.
• Details: 4 to 6 ft tall. Strong stems and a good cut flower.
• Habitat: The New Millennium breeding offers more heat tolerance than older varieties.
• Landscaping: Back of the border, adds a softer color.
• DELPHINIUM 'Cobalt Dreams':
• Description: Intense cobalt blue flowers, semi-double to double, often with a white or striped bee.
• Details: Height: 5-6 feet. Strong stems.
• Habitat: Standard Delphinium requirements; benefits from New Millennium breeding.
• Landscaping: Creates a vibrant, eye-catching display.
• Medium Delphiniums (2.5-5 feet): Graceful and Versatile This group includes the D. belladonna varieties, known for their more loosely branched flower spikes and bushier habit. They generally do not require staking and are more heat-tolerant than the tall hybrids. They offer a more relaxed, informal look.
• D. belladonna Hybrids:
• 'Belladonna': Classic sky-blue, single flowers.
• 'Casa Blanca': A pure white counterpart to 'Belladonna'.
• 'Bellamosum': Deep blue, single flowers.
• Connecticut Yankee: An older, reliable mix particularly well-suited to hotter summers. Offers a mix of blue, violet, and white flowers on 30-inch stems.
• Magic Fountains Series: Essentially a dwarf version of Pacific Giants, with the same large, double flowers but on shorter, 2-3 foot spikes. Excellent for smaller gardens or containers.
• 'Sky Blue' (with a white bee): A classic and popular choice.
• 'Cherry Blossom' (pink with a white bee): Adds a delicate, romantic touch.
• 'Dark Blue/Dark Bee': Creates deep contrast.
• Clear Springs Series: A newer series that falls between Pacific Giants and Magic Fountains in height. Strong stems make these varieties particularly good for cut flowers.
• DELPHINIUM 'Black Eyed Angels':
• Description: Pure white, semi-double flowers with a striking black bee.
• Details: Height: 2.5-3 feet (Magic Fountains series). Compact habit.
• Habitat: Standard Delphinium requirements; good for smaller gardens.
• Landscaping: Front of the border, containers, excellent contrast.
• DELPHINIUM 'Blue Buccaneers':
• Description: Deep blue-violet semi double flowers with a dark bee.
• Details: Height: 3-4 feet.
• Habitat: Good for smaller gardens.
• Landscaping: mid-border containers.
• Dwarf Delphiniums (2 feet or less): Compact Charm These petite delphiniums are perfect for the front of the border, containers, or rock gardens. While they lack the towering presence of the tall varieties, they offer vibrant color and are often better adapted to warmer climates.
• D. grandiflorum Varieties:
• 'Blue Butterfly': Features electric blue, single flowers loosely clustered on 15-inch spikes. Known for its long bloom time in cooler zones (3-6).
• 'Blue Mirror': Brilliant gentian blue, single flowers on 2-foot spikes. Also blooms well throughout the summer in cooler climates.
• Other Dwarf Species:
• D. zalil: Offers a unique color for delphiniums – yellow! Compact plants with deeply cut foliage and single yellow flowers on 2-foot spikes. Shorter-lived and can be more challenging to grow.
• D. cardinale: A California native with red, spurred flowers on 2-foot spikes. Also shorter-lived and requires specific growing conditions.
• DELPHINIUM elatum 'Violets Are Blue':
• Description: Intense violet-blue, single flowers. D. elatum type but bred for compactness.
• Details: Height: 12-18 inches. Long blooming.
• Habitat: Good heat tolerance for a D. elatum type.
• Landscaping: Excellent for edging, front of the border, containers.
• DELPHINIUM 'Mini Pinks':
• Description: Soft pink, semi-double flowers. Compact habit.
• Details: Height: 12-18 inches.
• Habitat: Standard Delphinium requirements.
• Landscaping: Front of the border, containers, adds a delicate touch.

Important Notes:

• Naming Conventions: Delphinium naming can be confusing. Series names (like "New Millennium") often encompass multiple cultivars with different colors. Always check the specific cultivar name for accurate information.
• Local Adaptation: Even with heat-tolerant varieties, it is always best to consult with local nurseries or experienced gardeners in your area to determine which delphiniums perform best in your specific climate.

Cultivating Delphinium Success: Growing Tips

Delphiniums thrive in well-drained soil with a slightly alkaline pH (6.5 to 7.0). Here is a guide to successful cultivation:

• Starting from Seed: Delphinium seed has a short shelf life, so use fresh seed. Sow indoors in January/February for spring planting, or August/September for fall planting (especially in warmer zones). Spring-sown seedlings may flower the first year, but blooms will be smaller and later.
• Planting: Choose a location with full sun (at least 6 hours) in cooler climates. In hotter areas, partial shade, especially during the hottest part of the day, is beneficial. Amend heavy clay soil with plenty of compost to improve drainage. Raised beds are highly recommended in areas with poor drainage. Space plants 1-2 feet apart, being careful not to bury the crown.
• Mulching: Apply a 4–6-inch layer of organic mulch (like shredded bark or compost) to conserve moisture, suppress weeds, and keep the roots cool.
• Fertilizing: Delphiniums are heavy feeders. Side-dress with compost or a balanced fertilizer (e.g., 5-10-5) at planting time, when flower stems begin to form, and again after flowering.
• Watering: Provide consistent moisture, especially during dry spells. Avoid overhead watering, which can promote fungal diseases.
• Deadheading: Cut off spent flower stalks immediately after blooming to encourage reblooming in the fall (in zones 3-6). This prevents the plant from putting energy into seed production.
• Staking (for tall varieties): Use stakes (bamboo, metal, or plastic-coated) and twine, tomato cages, linking stakes, or flower rings to support the heavy flower spikes of tall varieties. Place supports when plants are about a foot tall.
• Pest and Disease Control: Slugs and snails can be a problem, especially for young plants. Use appropriate control methods (e.g., beer traps, diatomaceous earth). Powdery mildew can occur; ensure good air circulation and avoid overhead watering.
• Winter Care: In colder climates, delphiniums are generally hardy. In very cold areas, a layer of mulch can provide extra protection. In warmer zones, treat them as annuals or choose heat-tolerant varieties.
• Dividing: In favorable climates the plants may live longer, even up to 10 years. These plants can be divided.

Heat Tolerance: A Key Consideration While most delphiniums are listed as hardy to USDA zones 3-8, they perform best in zones 3-6 or in cool-summer areas of zones 7 and 8. Consistent temperatures in the 90s (Fahrenheit) are detrimental to many traditional varieties, especially the tall hybrids.

For gardeners in hot-summer climates:

• Choose heat-tolerant varieties: The New Zealand New Millennium hybrids are an excellent choice. Dwarf varieties are also generally more heat-tolerant.
• Plant in the fall: This allows plants to establish themselves before the heat of summer arrives.
• Provide afternoon shade: This will protect plants from the most intense heat.
• Treat as annuals: If delphiniums struggle to survive the summer, consider growing them as annuals, planting new transplants each fall.

Understanding the different types of delphiniums and their specific needs, gardeners can enjoy these magnificent flowers in a wide range of climates and garden settings. The expanded range of sizes and improved heat tolerance make delphiniums a more accessible and rewarding choice than ever before.

By carefully selecting the right varieties and providing proper care, you can enjoy the majestic beauty of delphiniums in your garden, regardless of its size or location. The addition of specific cultivar information makes this guide even more useful for gardeners seeking to choose the perfect delphiniums for their needs.