How to Grow Blue Delphinium
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Blue Delphinium
Delphinium elatum
flowerBlue delphinium is a tall, majestic perennial flower prized for its spectacular spires of vibrant blue blooms that can reach heights of 3-6 feet. These dramatic flowering plants add vertical interest and elegance to garden landscapes and are excellent for cut flowers. They require cool growing conditions and well-draining soil to thrive.
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Example Blue Delphinium timeline · Pittsburgh, PA (Zone 6b)
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Plant Blue Delphinium
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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First Blue Delphinium blooms
Mid-to-late summerBefore the first fall frost (≈ Nov 8)
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Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 2-7; struggles in hot, humid climates (zones 8+)
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Get my Blue Delphinium timeline →Growth Stages
Germination & Seedling
3-4 weeksTiny seedlings with 2-4 true leaves emerge. Growth is slow in first weeks.
Provide bright light and cool temperatures (60-70°F). Keep soil consistently moist but not waterlogged. Thin seedlings to prevent damping off.
Vegetative Growth
6-8 months (first year)Plant develops sturdy stems and deeply lobed, attractive foliage. No flowering occurs in first year from seed.
Stake plants early to prevent wind damage as they grow tall. Fertilize monthly with balanced fertilizer. Remove weeds. Mulch around base.
Flowering
6-8 weeks (early to mid-summer)Tall spires (3-6 feet) with densely packed blue flowers open from bottom to top. Blooms are typically single or double depending on variety.
Provide sturdy stakes or support cages. Deadhead spent flowers to encourage continued blooming. Water regularly during blooming period. Fertilize every 2 weeks.
Seed Development & Decline
4-6 weeksFlowers fade and develop seed pods. Foliage begins to yellow and decline as plant enters dormancy.
Allow some flowers to go to seed if you want self-sowing. Cut back dead foliage in late fall. Do not leave standing dead material (encourages disease).
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Spray with insecticidal soap or horticultural oil in early morning. Increase humidity slightly. Remove heavily infested leaves.
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Hand-pick in early morning. Use copper tape around stem bases. Apply iron phosphate-based slug bait. Create barriers with diatomaceous earth.
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Ensure good air circulation by spacing plants adequately. Avoid wetting foliage. Spray with sulfur or fungicide at first sign. Remove infected leaves.
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Remove infected foliage. Avoid overhead watering. Apply fungicide if severe. Clean up fallen leaves in fall.
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Remove and destroy infested stems. Keep plants vigorous with proper watering and fertilizing. Prune out weak, damaged growth.
Uses
Edible Flowers
CulinaryBlue delphinium flowers are sometimes used as edible garnishes in gourmet cuisine, adding color and mild flavor to desserts and cocktails. However, use only ornamental varieties confirmed safe; some delphiniums contain toxic alkaloids. [source]
Cut Flowers & Floral Design
CraftDelphinium is a premier cut flower prized by florists for tall arrangements, wedding bouquets, and formal displays. The dramatic height and color range make it essential in the floral industry. [source]
Traditional Herbal Uses
MedicinalHistorically, delphinium was used in traditional medicine for various ailments, though modern use is limited due to alkaloid toxicity. Historical herbals document its use in folk remedies. [source]
Garden Design & Ornament
HouseholdDelphinium creates stunning vertical focal points in cottage gardens, borders, and formal landscapes. Its tall spires provide structure and color to garden compositions. [source]
Pollinator Attraction
WildlifeBlue delphinium flowers attract bees, butterflies, and hummingbirds, making them valuable for pollinator gardens and supporting native insect populations. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Cut flowers for arrangements in early morning when stems are turgid. Harvest when the lower 1/3 of the flower spike is open and upper buds are showing color. Re-cut stems at an angle indoors and change water every 2 days. Flowers last 7-10 days in a vase. For seed saving, allow flowers to mature and dry on the plant, then collect seed pods before they split.
Fun Facts
- 🌱 Delphinium flowers contain toxic alkaloids (delphinine and other compounds) and are poisonous if ingested by humans or livestock; all parts of the plant should be considered toxic.
- 🌱 The name 'delphinium' comes from the Greek word 'delphis' (dolphin) because the flower's spur resembles a dolphin's nose.
- 🌱 Blue delphiniums have been cultivated for over 400 years and were favorite flowers of Victorian gardeners who selectively bred taller varieties with increasingly dramatic flower forms.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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